![Introduction 5
that found in the food, drug, and cosmetic industries, that mechanization was first
applied on a large scale.
Estimates of the proportion of mass-produced durable goods to the total
production of durable goods range from 15 to 20%. It is not surprising, therefore,
that only about 5% of products are automatically assembled, the remainder being
assembled manually. As a result, since World War II, increasing attention has
been given to the possibility of using robots in assembly work. It was felt that,
because robots are basically versatile and reprogrammable, they could be applied
in small- and medium-batch manufacturing situations, which form over 80% of
all manufacture.
According to Schwartz [1], George Devol, Jr., patented a programmable
transfer device in 1954, which served as the basis for the modern industrial robot.
The first modern industrial robot, the Unimate [2] was conceived in 1956 at a
meeting between inventors George Devol and Joseph Engelberger. In 1961 the
Unimate joined the assembly line at General Motors handling die castings.
The first uses of industrial robots were in materials handling such as die-
casting and punch-press operations, and by 1968 they started to be used in
assembly. By 1972, more than 30 different robots were available from 15 man-
ufacturers.
In spite of these developments, mechanical and electromechanical assemblies
remain difficult to automate except in mass-production quantities. The exception
to this is the electronics industry, more specifically, the printed-circuit-board
(PCB) assembly. Because of the special nature of this product, introduced in the
early 1950s, it has been found possible to apply assembly automation even in
small-batch production.
At first, PCB components were hand-inserted and their leads hand-soldered.
To reduce the soldering time, wave-soldering was developed in which all the
leads are soldered in one pass of the board through the soldering machine. The
next step was automatic insertion of the component leads. Although initially most
small components were axial-lead components, several large electronics manu-
facturers developed multiple-lead insertion systems. The first company to produce
these systems commercially was USM (United Shoe Machinery).
The PCB is an ideal product for the application of assembly automation. It
is produced in vast quantities, albeit in a multitude of styles. Assembly of com-
ponents is carried out in the same direction, and the components types are limited.
With the standardization of components now taking place, a high proportion of
PCBs can be assembled entirely automatically. Also, the automatic-insertion
machines are easy to program and set up and can perform one to two insertions
per second. Consequently, relatively slow manual assembly is often economic
for only very small batches.
With the present widespread engineering trend toward replacing mechanical
control devices and mechanisms with electronics, PCB assembly automation is
now finding broad application; indeed, one of the principal applications of assem-
bly robots is the insertion of nonstandard (odd-form) electronic components that
cannot be handled by the available automatic-insertion machines.](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-29-320.jpg)
![6 Assembly Automation and Product Design
For many years, manufacturers of electrical and electronic products have
spent more on assembly technology than on any other industry [3].
1.2 CHOICE OF ASSEMBLY METHOD
When considering the manufacture of a product, a company must take into
account the many factors that affect the choice of assembly method. For a new
product, the following considerations are generally important:
1. Suitability of the product design
2. Production rate required
3. Availability of labor
4. Market life of the product
If the product has not been designed with automatic assembly in mind, manual
assembly is probably the only possibility. Similarly, automation will not be
practical unless the anticipated production rate is high. If labor is plentiful, the
degree of automation desirable will depend on the anticipated reduction in the
cost of assembly and the increase in production rate, assuming the increase can
be absorbed by the market. The capital investment in automatic machinery must
usually be amortized over the market life of the product. Clearly, if the market
life of the product is short, automation will be difficult to justify.
A shortage of assembly workers will often lead a manufacturer to consider
automatic assembly when manual assembly would be less expensive. This situ-
ation frequently arises when a rapid increase in demand for a product occurs.
Another reason for considering automation in a situation in which manual assem-
bly would be more economical is for research and development purposes, where
experience in the application of new equipment and techniques is considered
desirable. Many of the early applications of assembly robots were conducted on
this basis.
Following are some of the advantages of automation applied in appropriate
circumstances:
1. Increased productivity and reduction in costs
2. A more consistent product with higher reliability
3. Removal of operators from hazardous operations
4. The opportunity to reconsider the design of the product
The cost elements for equipment investments that assemblers target change
little over the years [3] (Figure 1.1). Direct labor has always been the number one
cost that manufacturers hope to reduce by purchasing assembly technology [3].
Productivity is the relationship between the output of goods and services and
one or more of the inputs — labor, capital, goods, and natural resources. It is
expressed as a ratio of output to input. Both output and input can be measured
in different ways, none of them being satisfactory for all purposes. The most](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-30-320.jpg)
![8 Assembly Automation and Product Design
could wait more than a year before seeing a return. In 2001, only 56% could
afford to wait that long [3].
Productivity in manufacturing should be considered particularly important
because of the relatively high impact that this sector of industry has on the
generation of national wealth. In the U.S., manufacturing absorbs over 25% of
the nation’s workforce and is the most significant single item in the national
income accounts, contributing about 30% of the gross national product (GNP).
This figure is about nine times the contribution of agriculture and construction
and three times that of finance and insurance. In 1974, manufacturing industries
accounted for over two thirds of the wealth-producing activities of the U.S. [4].
Within manufacturing in the U.S., the discrete-parts or durable-goods industries
clearly form a major target for productivity improvements because these are
under direct attack from imports of economically priced high-quality items.
These industries manufacture farm, metal-working, electrical machinery and
equipment, home electronic and electrical equipment, engines, communications
equipment, motor vehicles, aircraft, ships, and photographic equipment. This
important group of industries contribute approximately 13% of the GNP, and
their output is 46% of that of the manufacturing sectors and 80% of that of the
durable-goods manufacturing industries. These industries are highly significant
in international trade, their output constituting 80% of total manufacturing
exports. However, these industries are not generally the highly efficient, highly
automated mass-production units that one is often led to believe they are. The
great bulk of the products of these industries are produced in small to medium
batches in inefficient factories by using relatively ancient machines and tools.
These industries typically depend on manual labor for the handling and assembly
of parts, labor provided with tools no more sophisticated than screwdrivers,
wrenches, and hammers. It is not surprising, therefore, that, as we have seen,
for a wide variety of manufacturing industries, assembly accounts for more than
50% of the total manufacturing cost of a product and more than 40% of the
labor force. This means that assembly should be given high priority in the
attempts to improve manufacturing productivity.
In the past, in most manufacturing industries, when a new product was
considered, careful thought was given to how the product would function, to its
appearance, and sometimes to its reliability. However, little thought was given to
how easily the product could be assembled and how easily the various parts could
be manufactured. This philosophy is often referred to as the “over the wall”
approach or “we design it, you make it.” In other words, there is an imaginary
wall between the design and manufacturing functions; designs are thrown over
the wall to manufacturing, as illustrated in Figure 1.2 [5]. This attitude is par-
ticularly serious as it affects assembly. The fundamental reason for this is that
most manufacturing of component parts is accomplished on machines that per-
form tasks that cannot be performed manually, whereas machines that can perform
even a small fraction of the selection, inspection, and manipulative capabilities
of a manual assembly worker are rare. This has resulted in great reliance on the
versatility of assembly workers, particularly in the design of a product.](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-32-320.jpg)
![10 Assembly Automation and Product Design
1.3 SOCIAL EFFECTS OF AUTOMATION
Much has been said and written regarding the impact of automation and robots
in industry. In the 1980s, newspapers and television gave us the impression that
all consumer products would soon be assembled by general-purpose robots.
Nothing could be further from the truth. Often, publicity such as this led many
an industrial manager to inquire why their own company was not using robots
in this way and to issue directives to investigate the possibility. An assembly
robot was then purchased, and suitable applications sought. This turned out to
be surprisingly difficult, and what usually followed was a full-scale development
of a robot assembly system so that the various problem areas could be uncovered.
The system thus developed was never meant to be economic although that was
not always admitted. In fact, assembly systems based on a single general-purpose
assembly robot that performs all the necessary assembly operations are difficult
to justify on economic grounds. The central reason for this is that the peripheral
equipment (feeders, grippers, etc.) needed to build an economic robot assembly
station had not yet been developed. The practical difficulties are severe, and so,
there is no justification for prophesying mass unemployment as a result of the
introduction of assembly robots. Moreover, history has shown that special-pur-
pose one-of-a-kind assembly automation (which is relatively easy although expen-
sive to apply) has not had the kind of impact that was feared 25 years ago. In
some limited areas, such as the spot welding of car bodies, industrial robots have
made a significant impact. Special-purpose robots (or programmable automatic
insertion machines) are now used in over 50% of PCB assembly. However, the
application of general-purpose robots in batch assembly is, like all other techno-
logical changes, taking place slowly. It should be understood that industrial robots
are simply one more tool in the techniques available to manufacturing engineers
for improving productivity in manufacturing.
Table 1.2 shows the results of a survey illustrating that as much is spent on
parts feeders as on assembly robots. Also, twice as much is spent on single-station
assembly systems that probably assemble two or three parts, and five times as
much on multistation assembly systems. [3]
Considering the overall picture, the robot is not proving to be a particularly
effective tool in assembly. Indeed, much greater improvements in manufacturing
productivity can be obtained by carefully considering ease of assembly during
the design of the products.
It is appropriate to address more carefully the fear that robots are going to
have serious adverse effects on employment in manufacturing. The following
quotation is taken from the evidence of a prominent industrialist addressing a
U.S. Senate subcommittee on labor and public welfare [6]:
From a technological point of view, automation is working, but the same cannot be
said so confidently from the human point of view. The technologists have done and
are doing their job. They have developed and are developing equipment that works](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-34-320.jpg)
![12 Assembly Automation and Product Design
corner 20 years ago and is still just around the corner! It is worth examining
these alarmist views a little more carefully because of the very real and adverse
effects they can have on public opinion. These views are generally based on two
false premises:
1. That the introduction of improved techniques for the manufacture of
goods produces rapid and significant changes in productivity
2. That improvements in productivity have an overall negative effect on
employment
History shows that the introduction of improved manufacturing techniques
takes place very slowly. With specific reference to assembly robots, an MIT
professor puts it as follows [7]:
There has been in recent years a great deal of publicity associated with robotics.
The implication has been that great progress is being made in implementing robot
technology to perform assembly tasks. In fact, progress during the last ten years
has been slow and steady. Present perception in the popular press is that robots are
about to take over many manufacturing tasks. Yet, there is a growing awareness
that this is not so. The rate of progress in this area is accelerating as more money
and more interest are being directed toward the problems.
The automated factory of the future is still many years away, and steps in that
direction are being taken at a pace which will allow us, if we so choose, to study
and make enlightened decisions about the effects of implementation of flexible
automation on unemployment, quality and structure of the work environment, and
quality of the workpiece produced.
Even though this statement is reasonable and considered, there is an impli-
cation in the last sentence that automation will have the effect of increasing
unemployment. Regarding this common premise, it has long been established [8]
that there is little, if any, correlation between productivity changes and changes
in employment. Employment problems in the U.S. auto industry, for example,
have mostly arisen from the lack of manufacturing productivity improvement
rather than the opposite. Certainly there is no evidence that manufacturing process
innovation is, on balance, adverse to employment.
In summarizing a study of technology and employment, Cyert and Mowery
[9] stated:
(i) Historically, technological change and productivity growth have been associated
with expanding rather than contracting total employment and rising earnings. The
future will see little change in this pattern. As in the past, however, there will be
declines in specific industries and growth in others, and some individuals will be
displaced. Technological changes in the U.S. economy is not the sole or even the
most important cause of these dislocations.](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-36-320.jpg)
![Introduction 13
(ii) The adoption of new technologies generally is gradual rather than sudden. The
employment impacts of new technologies are realized through the diffusion and
adoption of technology, which typically take a considerable amount of time. The
employment impacts of new technologies therefore are likely to be felt more grad-
ually than the employment impacts of other factors, such as changes in exchange
rates. The gradual pace of technological change should simplify somewhat the
development and implementation of adjustment policies to help affected workers.
(iii) Within today’s international economic environment, slow adoption by U.S.
firms (relative to other industrial nations) of productivity-increasing technologies
is likely to cause more job displacement than the rapid adoption of such technolo-
gies. Much of the job displacement since 1980 does not reflect a sudden increase
in the adoption of labor saving innovations but instead is due in part to increased
U.S. imports and sluggish exports, which in turn reflect macroeconomic forces (the
large U.S. budget deficit), slow adoption of some technologies in U.S. manufactur-
ing, and other factors.
(iv) Technology transfer increasingly incorporates significant research findings and
innovations. In many technologies, the U.S. no longer commands a significant lead
over industrial competitor nations. Moreover, the time it takes another country to
become competitive with U.S. industry or for U.S. firms to absorb foreign technol-
ogies has become shorter.
In conclusion, it can be said that justification for the use of assembly auto-
mation equipment can be made on economic grounds (which is quite difficult to
do) or because the supply of local manual labor becomes inadequate to meet the
demand. In the past, the latter has most often been the real justification, without
completely disregarding the first, of course. Thus, the real social impact of the
use of robots in assembly is unlikely to be of major proportions.
Turning to the effects of product design, it can be stated that improvements
in product design leading to greater economy in the manufacture of parts and the
assembly of products will always result in improvements in both labor and total
productivity. To design a product for ease of assembly requires no expenditure
on capital equipment, and yet the significant reductions in assembly times have
a marked effect on productivity.
In fact, the design of products for ease of assembly has much greater potential
for reducing costs and improving productivity than assembly automation [10].
This is illustrated by the example shown in Figure 1.3. This graph shows clearly
that automation becomes less attractive as the product design is improved. For
the original design manufactured in large volumes, high-speed assembly automa-
tion would give an 86% reduction in assembly costs and, for medium production
volumes, robot assembly would give a 61% reduction. However, with the most
efficient design consisting of only two parts, design for assembly (DFA) gives a
92% reduction in manual assembly costs and, for this design, the further benefits
obtained through automation are negligible.](https://image.slidesharecdn.com/97343-250224035504-a6b21e68/85/Assembly-Automation-and-Product-Design-12th-Edition-Geoffrey-Boothroyd-37-320.jpg)
Assembly Automation and Product Design 12th Edition Geoffrey Boothroyd
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- 5. Assembly Automation and Product Design 12th Edition Geoffrey Boothroyd Digital Instant Download Author(s): Geoffrey Boothroyd ISBN(s): 9780824785475, 0824785479 Edition: 12 File Details: PDF, 19.58 MB Year: 2005 Language: english
- 7. Assembly Automation and Product Design Second Edition
- 8. MANUFACTURING ENGINEERING AND MATERIALS PROCESSING A Series of Reference Books and Textbooks SERIES EDITOR Geoffrey Boothroyd Boothroyd Dewhurst, Inc. Wakefield, Rhode Island 1. Computers in Manufacturing, U. Rembold, M. Seth, and J. S. Weinstein 2. Cold Rolling of Steel, William L. Roberts 3. Strengthening of Ceramics: Treatments, Tests, and Design Applications, Harry P. Kirchner 4. Metal Forming: The Application of Limit Analysis, Betzalel Avitzur 5. Improving Productivity by Classification, Coding, and Data Base Standardization: The Key to Maximizing CAD/CAM and Group Technology, William F. Hyde 6. Automatic Assembly, Geoffrey Boothroyd, Corrado Poli, and Laurence E. Murch 7. Manufacturing Engineering Processes, Leo Alting 8. Modern Ceramic Engineering: Properties, Processing, and Use in Design, David W. Richerson 9. Interface Technology for Computer-Controlled Manufacturing Processes, Ulrich Rembold, Karl Armbruster, and Wolfgang Ülzmann 10. Hot Rolling of Steel, William L. Roberts 11. Adhesives in Manufacturing, edited by Gerald L. Schneberger 12. Understanding the Manufacturing Process: Key to Successful CAD/CAM Implementation, Joseph Harrington, Jr. 13. Industrial Materials Science and Engineering, edited by Lawrence E. Murr 14. Lubricants and Lubrication in Metalworking Operations, Elliot S. Nachtman and Serope Kalpakjian 15. Manufacturing Engineering: An Introduction to the Basic Functions, John P. Tanner 16. Computer-Integrated Manufacturing Technology and Systems, Ulrich Rembold, Christian Blume, and Ruediger Dillman 17. Connections in Electronic Assemblies, Anthony J. Bilotta 18. Automation for Press Feed Operations: Applications and Economics, Edward Walker
- 9. 19. Nontraditional Manufacturing Processes, Gary F. Benedict 20. Programmable Controllers for Factory Automation, David G. Johnson 21. Printed Circuit Assembly Manufacturing, Fred W. Kear 22. Manufacturing High Technology Handbook, edited by Donatas Tijunelis and Keith E. McKee 23. Factory Information Systems: Design and Implementation for CIM Management and Control, John Gaylord 24. Flat Processing of Steel, William L. Roberts 25. Soldering for Electronic Assemblies, Leo P. Lambert 26. Flexible Manufacturing Systems in Practice: Applications, Design, and Simulation, Joseph Talavage and Roger G. Hannam 27. Flexible Manufacturing Systems: Benefits for the Low Inventory Factory, John E. Lenz 28. Fundamentals of Machining and Machine Tools: Second Edition, Geoffrey Boothroyd and Winston A. Knight 29. Computer-Automated Process Planning for World-Class Manufacturing, James Nolen 30. Steel-Rolling Technology: Theory and Practice, Vladimir B. Ginzburg 31. Computer Integrated Electronics Manufacturing and Testing, Jack Arabian 32. In-Process Measurement and Control, Stephan D. Murphy 33. Assembly Line Design: Methodology and Applications, We-Min Chow 34. Robot Technology and Applications, edited by Ulrich Rembold 35. Mechanical Deburring and Surface Finishing Technology, Alfred F. Scheider 36. Manufacturing Engineering: An Introduction to the Basic Functions, Second Edition, Revised and Expanded, John P. Tanner 37. Assembly Automation and Product Design, Geoffrey Boothroyd 38. Hybrid Assemblies and Multichip Modules, Fred W. Kear 39. High-Quality Steel Rolling: Theory and Practice, Vladimir B. Ginzburg 40. Manufacturing Engineering Processes: Second Edition, Revised and Expanded, Leo Alting 41. Metalworking Fluids, edited by Jerry P. Byers 42. Coordinate Measuring Machines and Systems, edited by John A. Bosch 43. Arc Welding Automation, Howard B. Cary 44. Facilities Planning and Materials Handling: Methods and Requirements, Vijay S. Sheth
- 10. 45. Continuous Flow Manufacturing: Quality in Design and Processes, Pierre C. Guerindon 46. Laser Materials Processing, edited by Leonard Migliore 47. Re-Engineering the Manufacturing System: Applying the Theory of Constraints, Robert E. Stein 48. Handbook of Manufacturing Engineering, edited by Jack M. Walker 49. Metal Cutting Theory and Practice, David A. Stephenson and John S. Agapiou 50. Manufacturing Process Design and Optimization, Robert F. Rhyder 51. Statistical Process Control in Manufacturing Practice, Fred W. Kear 52. Measurement of Geometric Tolerances in Manufacturing, James D. Meadows 53. Machining of Ceramics and Composites, edited by Said Jahanmir, M. Ramulu, and Philip Koshy 54. Introduction to Manufacturing Processes and Materials, Robert C. Creese 55. Computer-Aided Fixture Design, Yiming (Kevin) Rong and Yaoxiang (Stephens) Zhu 56. Understanding and Applying Machine Vision: Second Edition, Revised and Expanded, Nello Zuech 57. Flat Rolling Fundamentals, Vladimir B. Ginzburg and Robert Ballas 58. Product Design for Manufacture and Assembly: Second Edition, Revised and Expanded, Geoffrey Boothroyd, Peter Dewhurst, and Winston Knight 59. Process Modeling in Composites Manufacturing, edited by Suresh G Advani and E. Murat Sozer 60. Integrated Product Design and Manufacturing Using Geometric Dimensioning and Tolerancing, Robert Campbell 61. Handbook of Induction Heating, edited by Valery I. Rudnev, Don Loveless, Raymond Cook and Micah Black 62. Re-Engineering the Manufacturing System: Applying the Theory of Constraints, Second Edition, Robert Stein 63. Manufacturing: Design, Production, Automation, and Integration, Beno Benhabib 64. Rod and Bar Rolling: Theory and Applications, Youngseog Lee 65. Metallurgical Design of Flat Rolled Steels, Vladimir B. Ginzburg 66. Assembly Automation and Product Design: Second Edition, Geoffrey Boothroyd
- 11. Geoffrey Boothroyd Boothroyd Dewhurst, Inc. Wakefield, Rhode Island Assembly Automation and Product Design Second Edition Boca Raton London New York Singapore A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.
- 12. Published in 2005 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2005 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-10: 1-57444-643-6 (Hardcover) International Standard Book Number-13: 978-1-57444-643-2 (Hardcover) Library of Congress Card Number 2005041949 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registra- tion for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Boothroyd, G. (Geoffrey), 1932- Assembly automation and product design / Geoffrey Boothroyd. -- 2nd ed. p. cm. -- (Manufacturing engineering and materials processing ; 66) Includes bibliographical references and index. ISBN 1-57444-643-6 (alk. paper) 1. Assembly-line methods--Automation. I. Assembling machines. I. Title. II. Series TS178.4.B66 2005 670.42'7--dc22 2005041949 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Taylor & Francis Group is the Academic Division of T&F Informa plc.
- 13. Preface Portions of this book are based on a book published in 1968 under the title Mechanized Assembly by G. Boothroyd and A.H. Redford. In a later further edition, titled Automatic Assembly by G. Boothroyd, C. Poli, and L.E. Murch, the original material developed at the University of Salford in England was updated with work carried out at the University of Massachusetts. In those days, it was felt that manufacturing engineers and designers wished to learn about automatic assembly as it appeared to provide a means of improving productivity and competitiveness. Since 1978, I developed a subject that holds much greater promise for productivity improvement and cost reduction, namely, design for assembly (DFA). The DFA method has become widely used and has helped numerous companies introduce competitive product designs. This text, therefore, includes detailed discussions of design for assembly, and the subject of assembly automation is considered in parallel with that of product design. The first step in considering automation of assembly should be careful analysis of the product design for ease of automatic assembly. In addition, analysis of the product for ease of manual assembly should be carried out in order to provide the basis for economic comparisons of automation. Indeed, it is often found that if a product is designed appropriately, manual assembly is so inexpensive that automation cannot be justified. Thus, a whole chapter is devoted to design for manual assembly. Another chapter is devoted to design for high-speed automatic and robot assembly, and a third chapter deals with electronics assembly. This second edition includes, as an appendix, the popular Handbook of Feeding and Orienting Techniques for Small Parts published at the University of Massachusetts. This edition also includes the original data and coding systems for product design for high-speed automatic and robot assembly also developed at the University of Massachusetts. Finally, numerous problems have been added and worked solutions to all the problems are available. The book is intended to appeal to manufacturing and product engineers as well as to engineering students in colleges and universities. I wish to thank Dr. A.H. Redford for his kind permission to use material published in our original book, Mechanized Assembly, and to Drs. C.R. Poli and L.E. Murch for permission to include much of the material from the Handbook of Feeding and Orienting Techniques for Small Parts, which we coauthored.
- 14. Finally, thanks go to Dr. P. Dewhurst for his contributions to our work on product design for robot assembly. Geoffrey Boothroyd
- 15. The Author Geoffrey Boothroyd is Professor Emeritus of Industrial and Manufacturing Engi- neering at the University of Rhode Island in Kingston. The author or coauthor of more than 100 journal articles, he is also the coauthor or coeditor of several books, including Fundamentals of Machining and Machine Tools, Second Edition (with W.A. Knight), Automatic Assembly (with C. Poli and L.E. Murch), and Applied Engineering Mechanics (with C. Poli) (all titles published by Marcel Dekker.). Additionally, Professor Boothroyd serves as coeditor for the Taylor & Francis series Manufacturing Engineering and Materials Processing. A Fellow of the Society of Manufacturing Engineers, he is a member of the National Academy of Engineering, among other professional societies. Professor Booth- royd received Ph.D. (1962) and D.Sc. (1974) degrees in engineering from the University of London, England. His numerous honors and awards include the National Medal of Technology and the SME/ASME Merchant Medal.
- 17. Table of Contents Chapter 1 Introduction......................................................................................1 1.1 Historical Development of the Assembly Process......................................2 1.2 Choice of Assembly Method.......................................................................6 1.3 Social Effects of Automation ....................................................................10 References ...........................................................................................................15 Chapter 2 Automatic Assembly Transfer Systems ........................................17 2.1 Continuous Transfer ..................................................................................17 2.2 Intermittent Transfer..................................................................................17 2.3 Indexing Mechanisms................................................................................23 2.4 Operator-Paced Free-Transfer Machine....................................................27 References ...........................................................................................................28 Chapter 3 Automatic Feeding and Orienting — Vibratory Feeders .............29 3.1 Mechanics of Vibratory Conveying...........................................................29 3.2 Effect of Frequency...................................................................................34 3.3 Effect of Track Acceleration .....................................................................34 3.4 Effect of Vibration Angle ..........................................................................35 3.5 Effect of Track Angle................................................................................35 3.6 Effect of Coefficient of Friction................................................................37 3.7 Estimating the Mean Conveying Velocity.................................................38 3.8 Load Sensitivity.........................................................................................42 3.9 Solutions to Load Sensitivity....................................................................44 3.10 Spiral Elevators..........................................................................................46 3.11 Balanced Feeders.......................................................................................47 3.12 Orientation of Parts ...................................................................................47 3.13 Typical Orienting System..........................................................................48 3.14 Effect of Active Orienting Devices on Feed Rate....................................54 3.15 Analysis of Orienting Systems..................................................................55 3.15.1 Orienting System...........................................................................57 3.15.2 Method of System Analysis ..........................................................58 3.15.3 Optimization ..................................................................................61 3.16 Performance of an Orienting Device ........................................................63 3.16.1 Analysis .........................................................................................63 3.17 Natural Resting Aspects of Parts for Automatic Handling ......................69
- 18. 3.17.1 Assumptions ..................................................................................70 3.17.2 Analysis for Soft Surfaces ............................................................71 3.17.3 Analysis for Hard Surfaces ...........................................................77 3.17.4 Analysis for Cylinders and Prisms with Displaced Centers of Mass.............................................................................78 3.17.5 Summary of Results ......................................................................78 3.18 Analysis of a Typical Orienting System...................................................78 3.18.1 Design of Orienting Devices.........................................................85 3.19 Out-of-Bowl Tooling .................................................................................87 References ...........................................................................................................89 Chapter 4 Automatic Feeding and Orienting — Mechanical Feeders..........91 4.1 Reciprocating-Tube Hopper Feeder ..........................................................92 4.1.1 General Features............................................................................94 4.1.2 Specific Applications.....................................................................94 4.2 Centerboard Hopper Feeder ......................................................................94 4.2.1 Maximum Track Inclination..........................................................94 4.2.2 Load Sensitivity and Efficiency ....................................................99 4.3 Reciprocating-Fork Hopper Feeder.........................................................100 4.4 External Gate Hopper Feeder..................................................................102 4.4.1 Feed Rate.....................................................................................102 4.4.2 Load Sensitivity and Efficiency ..................................................106 4.5 Rotary-Disk Feeder .................................................................................108 4.5.1 Indexing Rotary-Disk Feeder......................................................108 4.5.2 Rotary-Disk Feeder with Continuous Drive ...............................109 4.5.3 Load Sensitivity and Efficiency ..................................................110 4.6 Centrifugal Hopper Feeder......................................................................110 4.6.1 Feed Rate.....................................................................................111 4.6.2 Efficiency.....................................................................................114 4.7 Stationary-Hook Hopper Feeder .............................................................115 4.7.1 Design of the Hook .....................................................................115 4.7.2 Feed Rate.....................................................................................118 4.8 Bladed-Wheel Hopper Feeder.................................................................119 4.9 Tumbling-Barrel Hopper Feeder.............................................................119 4.9.1 Feed Rate.....................................................................................121 4.10 Rotary-Centerboard Hopper Feeder........................................................124 4.11 Magnetic-Disk Feeder .............................................................................124 4.12 Elevating Hopper Feeder.........................................................................125 4.13 Magnetic Elevating Hopper Feeder ........................................................126 4.14 Magazines................................................................................................126 References .........................................................................................................130
- 19. Chapter 5 Feed Tracks, Escapements, Parts-Placement Mechanisms, and Robots ............................................................131 5.1 Gravity Feed Tracks ................................................................................131 5.1.1 Analysis of Horizontal-Delivery Feed Track..............................132 5.1.2 Example.......................................................................................137 5.1.3 On/Off Sensors ............................................................................139 5.1.3.1 Theory ..........................................................................140 5.1.4 Feed Track Section......................................................................143 5.1.5 Design of Gravity Feed Tracks for Headed Parts ......................146 5.1.5.1 Analysis........................................................................146 5.1.5.2 Results ..........................................................................153 5.1.5.3 Procedure for Use of Figure 5.17 to Figure 5.20........158 5.2 Powered Feed Tracks ..............................................................................158 5.2.1 Example.......................................................................................160 5.3 Escapements ............................................................................................161 5.3.1 Ratchet Escapements...................................................................162 5.3.2 Slide Escapements.......................................................................164 5.3.3 Drum Escapements......................................................................165 5.3.4 Gate Escapements........................................................................167 5.3.5 Jaw Escapements.........................................................................167 5.4 Parts-Placing Mechanisms.......................................................................168 5.5 Assembly Robots.....................................................................................171 5.5.1 Terminology.................................................................................171 5.5.2 Advantages of Robot Assembly..................................................172 5.5.3 Magazines....................................................................................174 5.5.4 Types of Magazine Systems........................................................175 5.5.5 Automatic Feeders for Robot Assembly.....................................175 5.5.6 Economics of Part Presentation ..................................................178 5.5.7 Design of Robot Assembly Systems...........................................182 References .........................................................................................................186 Chapter 6 Performance and Economics of Assembly Systems...................187 6.1 Indexing Machines ..................................................................................187 6.1.1 Effect of Parts Quality on Downtime .........................................187 6.1.2 Effects of Parts Quality on Production Time..............................188 6.1.3 Effect of Parts Quality on the Cost of Assembly.......................190 6.2 Free-Transfer Machines...........................................................................195 6.2.1 Performance of a Free-Transfer Machine...................................196 6.2.2 Average Production Time for a Free-Transfer Machine.............200 6.2.3 Number of Personnel Needed for Fault Correction ...................200 6.3 Basis for Economic Comparisons of Automation Equipment ...............201 6.3.1 Basic Cost Equations...................................................................202
- 20. 6.4 Comparison of Indexing and Free-Transfer Machines...........................204 6.4.1 Indexing Machine........................................................................204 6.4.2 Free-Transfer Machine ................................................................205 6.4.3 Effect of Production Volume.......................................................205 6.5 Economics of Robot Assembly...............................................................207 6.5.1 Parts Presentation ........................................................................208 6.5.2 Profile of Typical Candidate Assembly ......................................211 6.5.3 Single-Station Systems................................................................212 6.5.3.1 Equipment Costs ..........................................................212 6.5.3.2 Personnel Costs............................................................213 6.5.3.3 Parts Quality.................................................................213 6.5.3.4 Basic Cost Equation.....................................................214 6.5.4 Multistation Transfer Systems.....................................................215 6.5.4.1 Equipment Costs ..........................................................215 6.5.4.2 Cost Equation...............................................................216 References .........................................................................................................217 Chapter 7 Design for Manual Assembly......................................................219 7.1 Introduction..............................................................................................219 7.2 Where Design for Assembly Fits in the Design Process .......................219 7.3 General Design Guidelines for Manual Assembly.................................221 7.3.1 Design Guidelines for Part Handling..........................................221 7.3.2 Design Guidelines for Insertion and Fastening ..........................222 7.4 Development of a Systematic DFA Analysis Method............................227 7.5 DFA Index ...............................................................................................229 7.6 Classification System for Manual Handling...........................................230 7.7 Classification System for Manual Insertion and Fastening....................233 7.8 Effect of Part Symmetry on Handling Time...........................................236 7.9 Effect of Part Thickness and Size on Handling Time............................237 7.10 Effect of Weight on Handling Time........................................................239 7.11 Parts Requiring Two Hands for Manipulation........................................240 7.12 Effects of Combinations of Factors ........................................................240 7.13 Threaded Fasteners..................................................................................240 7.14 Effects of Holding Down ........................................................................242 7.15 Problems with Manual Assembly Time Standards.................................242 7.16 Application of the DFA Method.............................................................244 7.16.1 Results of the Analysis................................................................248 7.17 Further General Design Guidelines ........................................................251 References .........................................................................................................254
- 21. Chapter 8 Product Design for High-Speed Automatic Assembly and Robot Assembly ..................................................257 8.1 Introduction..............................................................................................257 8.2 Design of Parts for High-Speed Feeding and Orienting ........................258 8.3 Example...................................................................................................263 8.4 Additional Feeding Difficulties...............................................................265 8.5 High-Speed Automatic Insertion.............................................................266 8.6 Example...................................................................................................269 8.7 Analysis of an Assembly.........................................................................271 8.8 General Rules for Product Design for Automation................................272 8.9 Design of Parts for Feeding and Orienting.............................................276 8.10 Summary of Design Rules for High-Speed Automatic Assembly.........280 8.10.1 Rules for Product Design............................................................280 8.10.2 Rules for the Design of Parts......................................................280 8.11 Product Design for Robot Assembly ......................................................281 8.11.1 Summary of Design Rules for Robot Assembly ........................287 References .........................................................................................................289 Chapter 9 Printed-Circuit-Board Assembly .................................................291 9.1 Introduction..............................................................................................291 9.2 Terminology.............................................................................................291 9.3 Assembly Process for PCBs....................................................................292 9.4 SMD Technology.....................................................................................301 9.5 Estimation of PCB Assembly Costs .......................................................302 9.6 Worksheet and Database for PCB Assembly Cost Analysis..................303 9.6.1 Instructions ..................................................................................303 9.7 PCB Assembly — Equations and Data for Total Operation Cost .........305 9.7.1 Manual.........................................................................................306 9.7.2 Autoinsertion Machine................................................................306 9.7.3 Robot Insertion Machine.............................................................306 9.8 Glossary of Terms ...................................................................................308 References .........................................................................................................310 Chapter 10 Feasibility Study for Assembly Automation...............................311 10.1 Machine Design Factors to Reduce Machine Downtime Due to Defective Parts ............................................................................312 10.2 Feasibility Study......................................................................................313 10.2.1 Precedence Diagrams ..................................................................314 10.2.2 Manual Assembly of Plug...........................................................317
- 22. 10.2.3 Quality Levels of Parts................................................................318 10.2.4 Parts Feeding and Assembly .......................................................319 10.2.5 Special-Purpose Machine Layout and Performance...................321 10.2.5.1 Indexing Machine.........................................................321 10.2.5.2 Free-Transfer Machine.................................................324 10.2.6 Robot Assembly of the Power Plug............................................326 References .........................................................................................................332 Problems...........................................................................................................333 Appendix A Simple Method for the Determination of the Coefficient of Dynamic Friction ...............................................363 A.1 The Method .............................................................................................363 A.2 Analysis ...................................................................................................365 A.3 Precision of the Method..........................................................................366 A.4 Discussion................................................................................................366 Reference...........................................................................................................368 Appendix B Out-of-Phase Vibratory Conveyors ...........................................369 B.1 Out-of-Phase Conveying .........................................................................370 B.2 Practical Applications..............................................................................372 Reference...........................................................................................................373 Appendix C Laboratory Experiments ............................................................375 C.1 Performance of a Vibratory-Bowl Feeder...............................................375 C.1.1 Objectives ....................................................................................375 C.1.2 Equipment....................................................................................375 C.1.3 Procedure.....................................................................................375 C.1.4 Theory..........................................................................................376 C.1.5 Presentation of Results................................................................378 C.2 Performance of a Horizontal-Delivery Gravity Feed Track...................379 C.2.1 Objectives ....................................................................................379 C.2.2 Equipment (Objective 1) .............................................................379 C.2.3 Theory (Objective 1) ...................................................................380 C.2.4 Procedure (Objective 1)...............................................................381 C.2.5 Results (Objective 1)...................................................................381 C.2.6 Equipment (Objective 2) .............................................................381 C.2.7 Theory (Objective 2) ...................................................................382 C.2.8 Procedure (Objective 2)...............................................................382 C.2.9 Results (Objective 2)...................................................................383 C.2.10 Conclusions..................................................................................383
- 23. Appendix D Feeding and Orienting Techniques for Small Parts..................385 D.1 Coding System ........................................................................................385 D.1.1 Introduction to the Coding System.............................................386 D.1.2 Coding Examples ........................................................................390 D.1.3 Sample Parts for Practice............................................................392 D.1.4 Analysis of the Coding of the Sample Parts ..............................393 D.1.5 Coding System for Small Parts...................................................395 D.2 Feeding and Orienting Techniques .........................................................408 D.3 Orienting Devices for Vibratory-Bowl Feeders......................................474 D.4 Nonvibratory Feeders ..............................................................................492 Nomenclature...................................................................................................501 Index .................................................................................................................507
- 25. 1 1 Introduction Since the beginning of the 19th century, the increasing need for finished goods in large quantities, especially in the armaments industries, has led engineers to search for and to develop new methods of manufacture or production. As a result of developments in the various manufacturing processes, it is now possible to mass-produce high-quality durable goods at low cost. One of the more important manufacturing processes is the assembly process that is required when two or more component parts are to be secured together. The history of assembly process development is closely related to the history of the development of mass-production methods. The pioneers of mass production are also the pioneers of modern assembly techniques. Their ideas and concepts have brought significant improvements in the assembly methods employed in high-volume production. However, although many aspects of manufacturing engineering, especially the parts fabrication processes, have been revolutionized by the application of automation, the technology of the basic assembly process has failed to keep pace. Table 1.1 shows that, 35 years ago in the U.S., the percentage of the total labor force involved in the assembly process varied from about 20% for the manufacture of farm machinery to almost 60% for the manufacture of telephone and telegraph equipment. Because of this, assembly costs often accounted for more than 50% of the total manufacturing costs. TABLE 1.1 Percentage of Production Workers Involved in Assembly Industry Percentage of Workers Involved in Assembly Motor vehicles 45.6 Aircraft 25.6 Telephone and telegraph 58.9 Farm machinery 20.1 Household refrigerators and freezers 32.0 Typewriters 35.9 Household cooking equipment 38.1 Motorcycles, bicycles, and parts 26.3 Source: From 1967 Census of Manufacturers, U.S. Bureau of the Census.
- 26. 2 Assembly Automation and Product Design Although during the last few decades, efforts have been made to reduce assembly costs by the application of high-speed automation and, more recently, by the use of assembly robots, success has been quite limited. Many workers assembling mechanical products are still using the same basic tools as those employed at the time of the Industrial Revolution. 1.1 HISTORICAL DEVELOPMENT OF THE ASSEMBLY PROCESS In the early days, the manufacture of the parts and their fitting and assembly were carried out by craftsmen who learned their trade as indentured apprentices. Each part would be tailored to fit its mating parts. Consequently, it was necessary for a craftsman to be an expert in all the various aspects of manufacture and assembly, and training a new craftsman was a long and expensive task. The scale of production was often limited by the availability of trained craftsmen rather than by the demand for the product. This problem was compounded by the reluctance of the craft guilds to increase the number of workers in a particular craft. The conduct of war, however, requires reliable weapons in large quantities. In 1798, the U.S. needed a large supply of muskets, and federal arsenals could not meet the demand. Because war with the French was imminent, it was not possible to obtain additional supplies from Europe. Eli Whitney, now recognized as one of the pioneers of mass production, offered to contract to make 10,000 muskets in 28 months. Although it took 101/2 years to complete the contract, Whitney’s novel ideas on mass production had been proved successfully. At first, Whitney designed templates for each part, but he could not find machinists capable of following the contours. Next, he developed a milling machine that could follow the templates, but hand-fitting of the parts was still necessary. Eventually, the factory at New Haven, CT, built especially for the manufacture of the muskets, added machines for producing interchangeable parts. These machines reduced the skills required by the various workers and allowed signif- icant increases in the rate of production. In an historic demonstration in 1801, Whitney surprised his distinguished visitors when he assembled a musket lock after selecting a set of parts from a random heap. The results of Eli Whitney’s work brought about three primary developments in manufacturing methods. First, parts were manufactured on machines, resulting in consistently higher quality than that of handmade parts. These parts were interchangeable and, as a consequence, assembly work was simplified. Second, the accuracy of the final product could be maintained at a higher standard. Third, production rates could be significantly increased. These concepts became known as the American system of manufacture. Oliver Evans’ concept of conveying materials from one place to another without manual effort led eventually to further developments in automation for assembly. In 1793, Evans used three types of conveyors in an automatic flour mill that required only two operators. The first operator poured grain into a hopper,
- 27. Introduction 3 and the second filled sacks with the flour produced by the mill. All the interme- diate operations were carried out automatically, with conveyors carrying the material from operation to operation. A significant contribution to the development of assembly methods was made by Elihu Root. In 1849, Root joined the company that was producing Colt six- shooters. Even though, at that time, the various operations of assembling the component parts were quite simple, he divided these operations into basic units that could be completed more quickly and with less chance of error. Root’s division of operations gave rise to the concept “divide the work and multiply the output.” Using this principle, assembly work was reduced to basic operations and, with only short periods of worker training, high efficiencies could be obtained. Frederick Winslow Taylor was probably the first person to introduce the methods of time and motion study to manufacturing technology. The object was to save the worker’s time and energy by making sure that the work and all things associated with the work were placed in the best positions for carrying out the required tasks. Taylor also discovered that any worker has an optimum speed of working that, if exceeded, results in a reduction in overall performance. Undoubtedly, the principal contributor to the development of modern pro- duction and assembly methods was Henry Ford. He described his principles of assembly in the following words: Place the tools and then the men in the sequence of the operations so that each part shall travel the least distance while in the process of finishing. Use work slides or some other form of carrier so that when a workman completes his operation he drops the part always in the same place which must always be the most convenient place to his hand — and if possible, have gravity carry the part to the next workman. Use sliding assembly lines by which parts to be assembled are delivered at conve- nient intervals, spaced to make it easier to work on them. These principles were gradually applied in the production of the Model T Ford automobile. The modern assembly-line technique was first employed in the assembly of a flywheel magneto. In the original method, one operator assembled a magneto in 20 min. It was found that when the process was divided into 29 individual operations carried out by different workers situated at assembly stations spaced along an assembly line, the total assembly time was reduced to 13 min 10 sec. When the height of the assembly line was raised by 8 in., the time was reduced to 5 min, which was only one fourth of the time required in the original process of assembly. This result encouraged Henry Ford to utilize his system of assembly in other departments of the factory, which were producing subassemblies for the car. Subsequently, this brought a continuous and rapidly increasing flow of
- 28. 4 Assembly Automation and Product Design subassemblies to those working on the main car assembly. It was found that these workers could not cope with the increased load, and it soon became clear that the main assembly would also have to be carried out on an assembly line. At first, the movement of the main assemblies was achieved simply by pulling them by a rope from station to station. However, even this development produced an amazing reduction in the total time of assembly from 12 hr 28 min to 5 hr 50 min. Eventually, a power-driven endless conveyor was installed; it was flush with the floor and wide enough to accommodate a chassis. Space was provided for workers either to sit or stand while they carried out their operations, and the conveyor moved at a speed of 6 ft/min past 45 separate workstations. With the introduction of this conveyor, the total assembly time was reduced to 93 min. Further improvements led to an even shorter overall assembly time and, eventu- ally, a production rate of 1 car every 10 sec of the working day was achieved. Although Ford’s target of production had been exceeded and the overall quality of the product had improved considerably, the assembled products some- times varied from the precise standards of the hand-built prototypes. Eventually, Ford adopted a method of isolating difficulties and correcting them in advance before actual mass production began. The method was basically to set up a pilot plant where a complete assembly line was installed in which were used the same tools, templates, forming devices, gauges, and even the same labor skills that would eventually be used for mass production. This method has now become the standard practice for all large assembly plants. The type of assembly system described in the preceding text is usually referred to as a manual assembly line, and it is still the most common method of assembling mass- or large-batch-produced products. Since the beginning of the 20th century, however, methods of replacing manual assembly workers by mechanical devices have been introduced. These devices take the form of auto- matic assembly devices or workheads with part-feeding mechanisms and, more recently, robots with part trays. Thus, in the beginning, automated screwdrivers, nut runners, riveters, spot- welding heads, and pick-and-place mechanisms were positioned on transfer devices that moved the assemblies from station to station. Each workhead was supplied with oriented parts either from a magazine or from an automatic feeding and orienting device, usually a vibratory-bowl feeder. The special single-purpose workheads could continually repeat the same operation, usually taking no more than a few seconds. This meant that completed assemblies were produced at rates on the order of 10–30/min. For two-shift working, this translates into an annual production volume of several million. Automation of this type was usually referred to as mechanization and because it could be applied only in mass production, its development was closely tied to certain industries such as those manufacturing armaments, automobiles, watches and clocks, and other consumer products. Mechanization was used in the manu- facture of individual items such as light bulbs and safety pins that are produced in large quantities. However, it was probably in process manufacturing, such as
- 29. Introduction 5 that found in the food, drug, and cosmetic industries, that mechanization was first applied on a large scale. Estimates of the proportion of mass-produced durable goods to the total production of durable goods range from 15 to 20%. It is not surprising, therefore, that only about 5% of products are automatically assembled, the remainder being assembled manually. As a result, since World War II, increasing attention has been given to the possibility of using robots in assembly work. It was felt that, because robots are basically versatile and reprogrammable, they could be applied in small- and medium-batch manufacturing situations, which form over 80% of all manufacture. According to Schwartz [1], George Devol, Jr., patented a programmable transfer device in 1954, which served as the basis for the modern industrial robot. The first modern industrial robot, the Unimate [2] was conceived in 1956 at a meeting between inventors George Devol and Joseph Engelberger. In 1961 the Unimate joined the assembly line at General Motors handling die castings. The first uses of industrial robots were in materials handling such as die- casting and punch-press operations, and by 1968 they started to be used in assembly. By 1972, more than 30 different robots were available from 15 man- ufacturers. In spite of these developments, mechanical and electromechanical assemblies remain difficult to automate except in mass-production quantities. The exception to this is the electronics industry, more specifically, the printed-circuit-board (PCB) assembly. Because of the special nature of this product, introduced in the early 1950s, it has been found possible to apply assembly automation even in small-batch production. At first, PCB components were hand-inserted and their leads hand-soldered. To reduce the soldering time, wave-soldering was developed in which all the leads are soldered in one pass of the board through the soldering machine. The next step was automatic insertion of the component leads. Although initially most small components were axial-lead components, several large electronics manu- facturers developed multiple-lead insertion systems. The first company to produce these systems commercially was USM (United Shoe Machinery). The PCB is an ideal product for the application of assembly automation. It is produced in vast quantities, albeit in a multitude of styles. Assembly of com- ponents is carried out in the same direction, and the components types are limited. With the standardization of components now taking place, a high proportion of PCBs can be assembled entirely automatically. Also, the automatic-insertion machines are easy to program and set up and can perform one to two insertions per second. Consequently, relatively slow manual assembly is often economic for only very small batches. With the present widespread engineering trend toward replacing mechanical control devices and mechanisms with electronics, PCB assembly automation is now finding broad application; indeed, one of the principal applications of assem- bly robots is the insertion of nonstandard (odd-form) electronic components that cannot be handled by the available automatic-insertion machines.
- 30. 6 Assembly Automation and Product Design For many years, manufacturers of electrical and electronic products have spent more on assembly technology than on any other industry [3]. 1.2 CHOICE OF ASSEMBLY METHOD When considering the manufacture of a product, a company must take into account the many factors that affect the choice of assembly method. For a new product, the following considerations are generally important: 1. Suitability of the product design 2. Production rate required 3. Availability of labor 4. Market life of the product If the product has not been designed with automatic assembly in mind, manual assembly is probably the only possibility. Similarly, automation will not be practical unless the anticipated production rate is high. If labor is plentiful, the degree of automation desirable will depend on the anticipated reduction in the cost of assembly and the increase in production rate, assuming the increase can be absorbed by the market. The capital investment in automatic machinery must usually be amortized over the market life of the product. Clearly, if the market life of the product is short, automation will be difficult to justify. A shortage of assembly workers will often lead a manufacturer to consider automatic assembly when manual assembly would be less expensive. This situ- ation frequently arises when a rapid increase in demand for a product occurs. Another reason for considering automation in a situation in which manual assem- bly would be more economical is for research and development purposes, where experience in the application of new equipment and techniques is considered desirable. Many of the early applications of assembly robots were conducted on this basis. Following are some of the advantages of automation applied in appropriate circumstances: 1. Increased productivity and reduction in costs 2. A more consistent product with higher reliability 3. Removal of operators from hazardous operations 4. The opportunity to reconsider the design of the product The cost elements for equipment investments that assemblers target change little over the years [3] (Figure 1.1). Direct labor has always been the number one cost that manufacturers hope to reduce by purchasing assembly technology [3]. Productivity is the relationship between the output of goods and services and one or more of the inputs — labor, capital, goods, and natural resources. It is expressed as a ratio of output to input. Both output and input can be measured in different ways, none of them being satisfactory for all purposes. The most
- 31. Introduction 7 common way of defining and measuring productivity is output per man-hour, usually referred to as labor productivity. This measure of productivity is easy to understand, and it is the only measure for which reliable data have been accu- mulated over the years. However, a more realistic way of defining productivity is the ratio of output to total input, usually referred to as total productivity. Total productivity is difficult to measure because it is not generally agreed how the various contributions of labor, machinery, capital, etc., should be weighed relative to each other. Also, it is possible to increase labor productivity while reducing the total productivity. To take a hypothetical example, suppose a company is persuaded to install a machine that costs $200,000 and that it effectively does a job that is the equivalent of one worker. The effect will be to raise the output per man-hour (increase labor productivity) because fewer workers will be needed to maintain the same output of manufactured units. However, because it is unlikely to be economical for a company to spend as much as $200,000 to replace one worker, the capital investment is not worthwhile, and it results in lower total productivity and increased costs. In the long run, however, economic considerations will be taken into account when investment in equipment or labor is made, and improvements in labor productivity will generally be accompanied by corresponding improve- ments in total productivity. According to recent surveys, shrinking product life cycles, tighter profit margins, and a slowing economy are forcing manufacturers to pay off capital equipment investments faster than ever before. In 1999, 64% of manufacturers FIGURE 1.1 Cost elements targeted for equipment investments. (From Assembly Survey, Assembly, December 2001. With permission.) Indirect labor 0 100 80 60 Percent of plants 40 20 Direct labor Scrap WIP Materials Warranty 18 25 36 49 56 86
- 32. 8 Assembly Automation and Product Design could wait more than a year before seeing a return. In 2001, only 56% could afford to wait that long [3]. Productivity in manufacturing should be considered particularly important because of the relatively high impact that this sector of industry has on the generation of national wealth. In the U.S., manufacturing absorbs over 25% of the nation’s workforce and is the most significant single item in the national income accounts, contributing about 30% of the gross national product (GNP). This figure is about nine times the contribution of agriculture and construction and three times that of finance and insurance. In 1974, manufacturing industries accounted for over two thirds of the wealth-producing activities of the U.S. [4]. Within manufacturing in the U.S., the discrete-parts or durable-goods industries clearly form a major target for productivity improvements because these are under direct attack from imports of economically priced high-quality items. These industries manufacture farm, metal-working, electrical machinery and equipment, home electronic and electrical equipment, engines, communications equipment, motor vehicles, aircraft, ships, and photographic equipment. This important group of industries contribute approximately 13% of the GNP, and their output is 46% of that of the manufacturing sectors and 80% of that of the durable-goods manufacturing industries. These industries are highly significant in international trade, their output constituting 80% of total manufacturing exports. However, these industries are not generally the highly efficient, highly automated mass-production units that one is often led to believe they are. The great bulk of the products of these industries are produced in small to medium batches in inefficient factories by using relatively ancient machines and tools. These industries typically depend on manual labor for the handling and assembly of parts, labor provided with tools no more sophisticated than screwdrivers, wrenches, and hammers. It is not surprising, therefore, that, as we have seen, for a wide variety of manufacturing industries, assembly accounts for more than 50% of the total manufacturing cost of a product and more than 40% of the labor force. This means that assembly should be given high priority in the attempts to improve manufacturing productivity. In the past, in most manufacturing industries, when a new product was considered, careful thought was given to how the product would function, to its appearance, and sometimes to its reliability. However, little thought was given to how easily the product could be assembled and how easily the various parts could be manufactured. This philosophy is often referred to as the “over the wall” approach or “we design it, you make it.” In other words, there is an imaginary wall between the design and manufacturing functions; designs are thrown over the wall to manufacturing, as illustrated in Figure 1.2 [5]. This attitude is par- ticularly serious as it affects assembly. The fundamental reason for this is that most manufacturing of component parts is accomplished on machines that per- form tasks that cannot be performed manually, whereas machines that can perform even a small fraction of the selection, inspection, and manipulative capabilities of a manual assembly worker are rare. This has resulted in great reliance on the versatility of assembly workers, particularly in the design of a product.
- 33. Introduction 9 For example, an assembly worker can quickly conduct a visual inspection of the part to be assembled and can discard obviously defective parts, whereas elaborate inspection systems would often be required to detect even the most obviously defective part. If an attempt is made to assemble a part that appears to be acceptable but is in fact defective, an assembly worker, after unsuccessfully trying to complete the assembly, can reject the part quickly without a significant loss in production. In automatic assembly, however, the part might cause a stoppage of an automatic workhead or robot, resulting in system downtime while the fault is located and corrected. On the other hand, if a part has only a minor defect, an assembly worker may be able to complete the assembly, but the resulting product may not be satisfactory. It is often suggested that one advantage of automatic assembly is that it ensures a product of consistently high quality because the machine cannot handle parts that do not conform to the required specifications. Another advantage is that automatic assembly forces ease of assembly to be considered in the design of the product. In some situations, assembly by manual workers would be hazardous because of high temperatures and the presence of toxic or even explosive substances. Under these circumstances, productivity and cost considerations become less important. FIGURE 1.2 Illustrating “over the wall” design. (From Munro, S., Illustrating “over the wall” design, private communication.)
- 34. 10 Assembly Automation and Product Design 1.3 SOCIAL EFFECTS OF AUTOMATION Much has been said and written regarding the impact of automation and robots in industry. In the 1980s, newspapers and television gave us the impression that all consumer products would soon be assembled by general-purpose robots. Nothing could be further from the truth. Often, publicity such as this led many an industrial manager to inquire why their own company was not using robots in this way and to issue directives to investigate the possibility. An assembly robot was then purchased, and suitable applications sought. This turned out to be surprisingly difficult, and what usually followed was a full-scale development of a robot assembly system so that the various problem areas could be uncovered. The system thus developed was never meant to be economic although that was not always admitted. In fact, assembly systems based on a single general-purpose assembly robot that performs all the necessary assembly operations are difficult to justify on economic grounds. The central reason for this is that the peripheral equipment (feeders, grippers, etc.) needed to build an economic robot assembly station had not yet been developed. The practical difficulties are severe, and so, there is no justification for prophesying mass unemployment as a result of the introduction of assembly robots. Moreover, history has shown that special-pur- pose one-of-a-kind assembly automation (which is relatively easy although expen- sive to apply) has not had the kind of impact that was feared 25 years ago. In some limited areas, such as the spot welding of car bodies, industrial robots have made a significant impact. Special-purpose robots (or programmable automatic insertion machines) are now used in over 50% of PCB assembly. However, the application of general-purpose robots in batch assembly is, like all other techno- logical changes, taking place slowly. It should be understood that industrial robots are simply one more tool in the techniques available to manufacturing engineers for improving productivity in manufacturing. Table 1.2 shows the results of a survey illustrating that as much is spent on parts feeders as on assembly robots. Also, twice as much is spent on single-station assembly systems that probably assemble two or three parts, and five times as much on multistation assembly systems. [3] Considering the overall picture, the robot is not proving to be a particularly effective tool in assembly. Indeed, much greater improvements in manufacturing productivity can be obtained by carefully considering ease of assembly during the design of the products. It is appropriate to address more carefully the fear that robots are going to have serious adverse effects on employment in manufacturing. The following quotation is taken from the evidence of a prominent industrialist addressing a U.S. Senate subcommittee on labor and public welfare [6]: From a technological point of view, automation is working, but the same cannot be said so confidently from the human point of view. The technologists have done and are doing their job. They have developed and are developing equipment that works
- 35. Introduction 11 miracles. But as is too often the case in this age of the widening gap between scientific progress and man’s ability to cope with it, we have failed to keep pace. Much of this failure is due, I think, to the existence of a number of myths about automation …. The most seductive of these is the claim that, for a number of reasons, automation is not going to eliminate many jobs …. Personally, I think … that automation is a major factor in eliminating jobs in the United States, at the rate of more than 40,000 per week, as previous estimates have put it. These observations are quoted from Senate hearings in 1963 — over 40 years ago! Even before that, in 1950, a famous Massachusetts Institute of Technology professor of mathematics, Norbert Wiener, stated: Let us remember that the automatic machine … is the precise economic equivalent of slave labor. Any labor which competes with slave labor must accept the economic conditions of slave labor. It is perfectly clear that this will produce an unemployment situation, in comparison with which … the depression of the thirties will seem a pleasant joke. In retrospect, it is amusing to look back at the serious predictions made by famous and influential individuals and see just how wrong they were. However, the problem is that equally famous people have been making similar pronounce- ments about the automatic factory, which was considered to be just around the TABLE 1.2 Spending on Assembly Equipment Equipment Type Percentage of Total Spending Estimated Total Dollars Spent ($M) Automated dispensing 4 85 Multistation assembly systems 26 556 Single-station assembly machines 10 213 Parts feeders 5 107 Conveyors 4 85 Power tools 9 192 Welding, soldering, and brazing 11 235 Robots 5 107 PCB assembly equipment 7 149 Test and inspection 10 213 Wire processing 3 64 Workstations and accessories 5 107 Other 1 21 TOTAL 100 2,134 Source: From Assembly Survey, Assembly, December 2001.
- 36. 12 Assembly Automation and Product Design corner 20 years ago and is still just around the corner! It is worth examining these alarmist views a little more carefully because of the very real and adverse effects they can have on public opinion. These views are generally based on two false premises: 1. That the introduction of improved techniques for the manufacture of goods produces rapid and significant changes in productivity 2. That improvements in productivity have an overall negative effect on employment History shows that the introduction of improved manufacturing techniques takes place very slowly. With specific reference to assembly robots, an MIT professor puts it as follows [7]: There has been in recent years a great deal of publicity associated with robotics. The implication has been that great progress is being made in implementing robot technology to perform assembly tasks. In fact, progress during the last ten years has been slow and steady. Present perception in the popular press is that robots are about to take over many manufacturing tasks. Yet, there is a growing awareness that this is not so. The rate of progress in this area is accelerating as more money and more interest are being directed toward the problems. The automated factory of the future is still many years away, and steps in that direction are being taken at a pace which will allow us, if we so choose, to study and make enlightened decisions about the effects of implementation of flexible automation on unemployment, quality and structure of the work environment, and quality of the workpiece produced. Even though this statement is reasonable and considered, there is an impli- cation in the last sentence that automation will have the effect of increasing unemployment. Regarding this common premise, it has long been established [8] that there is little, if any, correlation between productivity changes and changes in employment. Employment problems in the U.S. auto industry, for example, have mostly arisen from the lack of manufacturing productivity improvement rather than the opposite. Certainly there is no evidence that manufacturing process innovation is, on balance, adverse to employment. In summarizing a study of technology and employment, Cyert and Mowery [9] stated: (i) Historically, technological change and productivity growth have been associated with expanding rather than contracting total employment and rising earnings. The future will see little change in this pattern. As in the past, however, there will be declines in specific industries and growth in others, and some individuals will be displaced. Technological changes in the U.S. economy is not the sole or even the most important cause of these dislocations.
- 37. Introduction 13 (ii) The adoption of new technologies generally is gradual rather than sudden. The employment impacts of new technologies are realized through the diffusion and adoption of technology, which typically take a considerable amount of time. The employment impacts of new technologies therefore are likely to be felt more grad- ually than the employment impacts of other factors, such as changes in exchange rates. The gradual pace of technological change should simplify somewhat the development and implementation of adjustment policies to help affected workers. (iii) Within today’s international economic environment, slow adoption by U.S. firms (relative to other industrial nations) of productivity-increasing technologies is likely to cause more job displacement than the rapid adoption of such technolo- gies. Much of the job displacement since 1980 does not reflect a sudden increase in the adoption of labor saving innovations but instead is due in part to increased U.S. imports and sluggish exports, which in turn reflect macroeconomic forces (the large U.S. budget deficit), slow adoption of some technologies in U.S. manufactur- ing, and other factors. (iv) Technology transfer increasingly incorporates significant research findings and innovations. In many technologies, the U.S. no longer commands a significant lead over industrial competitor nations. Moreover, the time it takes another country to become competitive with U.S. industry or for U.S. firms to absorb foreign technol- ogies has become shorter. In conclusion, it can be said that justification for the use of assembly auto- mation equipment can be made on economic grounds (which is quite difficult to do) or because the supply of local manual labor becomes inadequate to meet the demand. In the past, the latter has most often been the real justification, without completely disregarding the first, of course. Thus, the real social impact of the use of robots in assembly is unlikely to be of major proportions. Turning to the effects of product design, it can be stated that improvements in product design leading to greater economy in the manufacture of parts and the assembly of products will always result in improvements in both labor and total productivity. To design a product for ease of assembly requires no expenditure on capital equipment, and yet the significant reductions in assembly times have a marked effect on productivity. In fact, the design of products for ease of assembly has much greater potential for reducing costs and improving productivity than assembly automation [10]. This is illustrated by the example shown in Figure 1.3. This graph shows clearly that automation becomes less attractive as the product design is improved. For the original design manufactured in large volumes, high-speed assembly automa- tion would give an 86% reduction in assembly costs and, for medium production volumes, robot assembly would give a 61% reduction. However, with the most efficient design consisting of only two parts, design for assembly (DFA) gives a 92% reduction in manual assembly costs and, for this design, the further benefits obtained through automation are negligible.
- 38. 14 Assembly Automation and Product Design This example reveals a kind of paradox created when designing a product for ease of automatic assembly. In many cases the product becomes so easy to assemble manually that this would become the most economic method of FIGURE 1.3 Example of the effect of automation and design for assembly. (From Boothroyd, G., Design for assembly — the key to design for manufacture, International Journal of Advanced Manufacturing Technology, Vol. 2, No. 3, 1987.) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Assembly cost ($) Automatic Robot M anual Annual production volumes: Robotic - 200,000 Automatic - 2,400,000 24 8 4 2 Number of parts 48 mm
- 39. Introduction 15 assembly. A practical example of this is the IBM Proprinter, which was introduced as an accessory to the PC. This printer was designed to be assembled using robots and, indeed, the design of the product was carried out in parallel with the design of the factory that would assemble them. When the IBM Proprinter was intro- duced, the ease of its assembly was demonstrated by manually assembling it in only 3 min. This was to be compared with the estimated assembly time of 30 min for the Japanese Epson printer, the previous dot matrix printer used as an accessory to the PC. However, as the robotic factory had already been built, this was the way the printer was assembled, whereas hindsight would indicate that manual assembly was probably the more economic approach. Indeed, it is under- stood that, eventually, this was the way the printer was assembled. In the following chapters, the basic components of assembly machines are presented, and the overall performance of assembly systems is discussed. Finally, detailed analyses of the suitability of parts and products for both manual and automatic assembly are presented. REFERENCES 1. Schwartz, W.H.,AnAssembly Hall of Fame, Assembly Engineering, January 1988. 2. Nof, S.Y. (Ed.), Handbook of Industrial Robots, 2nd ed., John Wiley & Sons, New York, 1999. 3. Assembly Survey, Assembly, December 2001. 4. The National Role and Importance of Manufacturing Engineering and Advanced Manufacturing Technology, position paper of the S.M.E. (Society of Manufactur- ing Engineers), May 8, 1978. 5. Munro, S., Illustrating “over the wall” design, private communication. 6. Terborgh, G., The Automation Hysteria, Norton, New York, 1965. 7. Seering, W.P. and Gordon, S.J., Review of Literature on Automated Assembly, Department of Mechanical Engineering, MIT, Cambridge, MA, November 1983 8. Aron, P., The Robot Scene in Japan: An Update, Report No. 26, Diawan Securities American, Inc., New York, 1983. 9. Cyert, R.M. and Mowery, D.C., Technology and Employment, National Academy Press, Washington, D.C., 1987. 10. Boothroyd, G., Design for Assembly — The Key to Design for Manufacture, International Journal of Advanced Manufacturing Technology, Vol. 2, No. 3, 1987.
- 41. 17 2 Automatic Assembly Transfer Systems In automatic assembly, the various individual assembly operations are generally carried out at separate workstations. For this method of assembly, a machine is required for transferring the partly completed assemblies from workstation to workstation, and a means must be provided to ensure that no relative motion exists between the assembly and the workhead or robot while the operation is being carried out. As the assembly passes from station to station, it is necessary that it be maintained in the required attitude. For this purpose, the assembly is usually built up on a base or work carrier, and the machine is designed to transfer the work carrier from station to station; an example of a typical work carrier is shown in Figure 2.1. Assembly machines are usually classified according to the system adopted for transferring the work carriers (Figure 2.2). Thus, an in-line assembly machine is one in which the work carriers are transferred in line along a straight slideway, and a rotary machine is one in which the work carriers move in a circular path. In both types of machine, the transfer of work carriers may be continuous or intermittent. 2.1 CONTINUOUS TRANSFER With continuous transfer, the work carriers are moving at a constant speed while the workheads keep pace. When the operations are completed, the workheads return to their original positions and, again, keep pace with the work carriers. Alternatively, the workheads move in a circular path tangential to the motion of the work carriers. In either case, the assembly operations are carried out during the period in which the workheads are keeping pace with the work carriers. Continuous-transfer systems have limited application in automatic assembly because the workheads and associated equipment are often heavy and must therefore remain stationary. It is also difficult to maintain sufficiently accurate alignment between the workheads and work carriers during the operation cycle because both are moving. Continuous-transfer machines are most common in industries such as food processing or cosmetics, where bottles and jars have to be filled with liquids. 2.2 INTERMITTENT TRANSFER Intermittent transfer is the system more commonly employed for automatic assembly. As the name implies, the work carriers are transferred intermittently, and the workheads remain stationary. Often, the transfer of all the work carriers
- 42. 18 Assembly Automation and Product Design FIGURE 2.1 Work carrier suitable for holding and transferring three-pin power plug base. FIGURE 2.2 Basic types of assembly machines. Assembly machines Continuous transfer (Workheads index) Intermittent transfer (Workheads stationary) Rotary In-line Rotary In-line Indexing Free transfer (In-line)
- 43. Automatic Assembly Transfer Systems 19 occurs simultaneously, and the carriers then remain stationary to allow time for the assembly operations. These machines may be termed indexing machines, and typical examples of the rotary and in-line types of indexing machines are shown in Figure 2.3 and Figure 2.4, respectively. With rotary indexing machines, index- ing of the table brings the work carriers under the various workheads in turn, and assembly of the product is completed during one revolution of the table. Thus, at the appropriate station, a completed product may be taken off the machine after each index. The in-line indexing machine works on a similar principle but, in this case, a completed product is removed from the end of the line after each index. With in-line machines, provision must be made for returning the empty work carriers to the beginning of the line. The transfer mechanism on in-line machines is generally one of two types: the shunting work carrier or the belt- driven work carrier. The shunting work carrier transfer system is shown in Figure 2.5. In this system, the work carriers have lengths equal to the distance moved during one index. Positions are available for work carriers at the beginning and end of the assembly line, where no assembly takes place. At the start of the cycle of operations, the work carrier position at the end of the line is vacant. A mechanism FIGURE 2.3 Rotary indexing machine (with one workhead shown). Parts feeder Stationary workhead Work carriers Indexing table
- 44. 20 Assembly Automation and Product Design pushes the line of work carriers up to a stop at the end of the line, and this indexes the work carriers’ position. The piston then withdraws, and the completed assem- bly at the end of the line is removed. The empty work carrier from a previous cycle that has been delivered by the return conveyor is raised into position at the beginning of the assembly line. Although the system described here operates in the vertical plane, the return of work carriers can also be accomplished in the horizontal plane. In this case, transfer from the assembly line to the return conveyor (and vice versa) is simpler, but greater floor area is used. In practice, when operating in the horizontal plane, it is more usual to dispense with the rapid return conveyor and to fit further assembly heads and associated transfer equipment in its place (Figure 2.6). However, this system has the disadvantage that access to the various workheads may be difficult. A further disadvantage with all shunting work carrier systems is that the work carriers themselves must be accurately manufactured. For example, if an error of 0.025 mm were to occur on the length of each work carrier in a 20-station machine, an error in alignment of 0.50 mm would occur at the last station. This error could create serious difficulties in the operation of the workheads. However, in all in-line transfer machines, it is usual for each work carrier, after transfer, to be finally positioned and locked by a locating plunger before the assembly operation is initiated. FIGURE 2.4 In-line indexing machine (with one workhead shown). Parts feeder Stationary workhead Completed assembly Work carriers indexed
- 45. Automatic Assembly Transfer Systems 21 The belt-driven work-carrier transfer system is illustrated in Figure 2.7. Basi- cally, this machine uses an indexing mechanism that drives a belt or flexible steel band to which the work carriers are attached. The work carriers are spaced to correspond to the distance between the workheads. Instead of attaching the work carriers rigidly to the belt, it is possible to employ a chain that has attachments to push the work carriers along guides. In this case, the chain index can be arranged to leave the work carriers short of their final position, allowing location plungers to bring them into line with the work- heads. FIGURE 2.5 In-line transfer machine with shunting work carriers returned in vertical plane. Parts feeder Base of assembly placed in position on work carrier Stationary workhead Empty work carrier returned rapidly on conveyer Empty work carrier lifted to beginning of line
- 46. Exploring the Variety of Random Documents with Different Content
- 47. Sul punto di salutarla, lei si chinò su di lui — oh, senza civetteria, senza impudicizia, ma ardentemente, umilmente. Egli ne rimase commosso nel profondo del suo gran cuore indulgente. Cingendola con le braccia, egli la baciò sulla bocca, e il bacio che gli fu reso, fu certo il più sincero che un uomo abbia mai ricevuto. — Dio mio! — singhiozzò lei. — Vorrei morire per voi! vorrei morire per voi! E si svincolò precipitosamente e salì le scale correndo. Egli si sentì gli occhi umidi di pianto. — Martin Eden, — confessò a se stesso, — tu non sei un bruto e non sei che un meschino nietzschiano. Se tu potessi, la sposeresti e riempiresti così di felicità quel povero cuore fremente. Ma non puoi! Tu non puoi! Che maledetta vergogna!... — Il povero vecchio vagabondo parla delle sue povere vecchie ulcere, — borbottò egli, ricordando Hanley, — Credo che la vita non sia che equivoci, e una vergogna. È vero: un equivoco e una vergogna.
- 48. CAPITOLO XLII. «La Vergogna del Sole» fu pubblicata in ottobre. Nel tagliare la cordicella che legava una mezza dozzina di copie mandate in omaggio dall’editore, Martin fu colto da pesante tristezza. Egli immaginò quale sarebbe stata la sua gioia delirante, mesi prima, e la paragonò all’indifferenza attuale. Il suo libro! il primo libro! E il polso non gli s’era accelerato, ed egli non provava altro che cupa tristezza! Che gl’importava, ormai?... C’era da aspettarsi del danaro, evidentemente, ed egli non sentiva la passione del danaro. Portò una copia in cucina e la porse a Maria, confusa e agitata. — È mio, — le disse. — Ho scritto questo libro nella mia camera, e, certo, le vostre buone minestre hanno molto contribuito. È vostro: un semplice ricordo. Egli era mosso dal pensiero di farle piacere, di renderla orgogliosa di lui, di giustificare la fiducia che lei non aveva cessato di manifestargli. Essa collocò il libro in salotto, accanto alla bibbia famigliare, come una cosa sacra, feticcio dell’amicizia. Ecco una cosa che attenuava la delusione di sapere il suo inquilino lavandaio; e sebbene essa non capisse neppure un rigo del libro, sentiva oscuramente che ogni frase ne era nobile e bella. Era una popolana, lei, semplice e terra terra, ma aveva un cuore bennato. Egli lesse con la stessa indifferenza le recensioni su «La Vergogna del Sole», che l’Argo della stampa gli mandava tutte le settimane. Il suo libro faceva chiasso, era evidente; il portafogli si arrotondava. Egli avrebbe potuto collocare Lizzie, liberarsi dei suoi impegni e avere ancora tanto da costruirsi il castello di verzura; Singletree, Darnley e
- 49. C., prudentemente, s’erano limitati a fare un’edizione di 1500 copie, ma, dopo le critiche favorevoli, ne fecero una seconda di 3000, poi una terza di 5000 copie. Una casa di Londra chiese il permesso, telegraficamente, per un’edizione inglese; e si seppe, nello stesso tempo, che in Francia, in Germania, in Isvezia, stavano preparando delle traduzioni. L’attacco alla scuola di Maeterlinck non poteva essere lanciato in un momento migliore. Sorsero delle polemiche vivacissime: Salceby e Haeckel erano per caso d’accordo nell’approvare e difendere «La Vergogna del Sole». Crookes e Wallace si schierarono contro, mentre Sir Oliver Lodge tentava una conciliazione in conformità delle sue teorie cosmiche. I discepoli di Maeterlinck si strinsero attorno allo stendardo del misticismo. Chesterton provocò un riso universale pubblicando una serie di saggi scritti da avversarî pazzi furiosi. Ma tutti, partigiani e nemici, furono schiacciati da una nota fulminante di Giorgio Bernardo Shaw. Inutile dire che l’arena era zeppa di combattenti meno illustri, che però non sollevarono meno polvere e facevano un chiasso e una confusione spaventose. «È un prodigio assolutamente sbalorditivo, — scrisse a Martin la Casa Singletree, Darnley e C. — il fatto d’un saggio filosofico e critico che si vende come un romanzo. Quest’opera è destinata a vincere tutti i records. «È qui incluso il duplicato d’un contratto per la vostra prossima opera. Vi preghiamo di osservare che abbiamo portato la vostra percentuale al 20%, che è quasi il massimo che una casa editrice possa offrire. Se l’offerta vi conviene, vi preghiamo di scrivere il titolo del vostro libro nello spazio riservato su questo foglio. Quanto all’argomento, vi lasciamo piena libertà: c’importa poco. Se avete un lavoro già pronto, tanto meglio. Bisogna battere il ferro sinchè è caldo. «Appena riceveremo il contratto firmato, avremo il piacere di mandarvi un anticipo di 25.000 lire, per darvi prova della nostra fiducia. Vorremmo anche discutere le clausole di un contratto per parecchi anni, — supponiamo dieci, — durante i quali il diritto
- 50. esclusivo alla pubblicazione di ogni vostra opera in volume sarebbe riservato a noi. Ma di questo, un’altra volta.» Martin mise la lettera da parte e, abbandonatosi a un calcolo mentale, concluse con questa scoperta, che 75 centesimi moltiplicati per sessantamila facevano 45.000 lire. Egli firmò il contratto, ne riempì lo spazio bianco col titolo «Il falò di gioia», e lo mandò agli editori, con le venti novelle scritte un tempo. E, per volta di posta, giunse lo chèque di 25.000 lire di Singletree, Darnley e C. — Volete venire con me in città, Maria, questo pomeriggio, verso le due? — propose Martin la mattina. — O, meglio, trovatevi all’angolo di Broadway con la 14ª strada, alle due. Mi troverete là. Essa fu puntuale. La sola spiegazione che lei avesse trovata per quel mistero fu la parola «scarpe», e la sua delusione fu grande, quando Martin, sorpassando una grande calzoleria, la trascinò in un’agenzia di compra-vendita d’immobili. Quel che avvenne poi fu come un sogno, e tale le rimase nella mente, sino alla morte. Dei bei signori le sorrisero con simpatia, mentre parlavano tra loro e con Martin, poi una macchina da scrivere fece udire il suo ticchettio, delle firme furono apposte appiè d’un documento imponente; il suo padrone di casa, chiamato, firmò anche lui. E quando tutto fu finito ed essi furono usciti, il suo padrone di casa le disse: — Ebbene, Maria, questo mese non dovrete pagarmi le 35 lire! — Maria, sbalordita, non sapeva che dire. — Neppure il mese prossimo, nè il seguente, nè l’altro, — continuò il proprietario. Essa ringraziò, con incoerenza, come d’un favore. E solo quando ritornarono a Nord Oakland, dopo aver conferito con amici e col droghiere portoghese, essa capì ch’era diventata proprietaria della casetta che abitava da tanto tempo. — Perchè non comperate più nulla da me? — domandò il droghiere portoghese a Martin, quel giorno, avvicinandolo, alla discesa dal tranvai. Martin spiegò che non cucinava più, e dovette entrare a bere un bicchiere. Egli osservò che quel vino era il migliore della cantina.
- 51. — Maria, — dichiarò Martin quella stessa sera, — vi lascio. E anche voi tra breve andrete via di qui. Voi affitterete la casa ad altri e ne riscuoterete la pigione. Mi avete detto che vostro fratello abita a San Leandro, Haywards o altrove, non ricordo: gli direte di venirmi a trovare. Sarò all’Hôtel Metropole a Oakland. Egli s’ìntende di belle fattorie e glie ne farò vedere una. Così Maria divenne proprietaria d’una casa in città e d’una fattoria in campagna, con due bifolchi per i lavori e un deposito in banca, che aumentava di giorno in giorno; e tutta la sua prole era provvista di scarpe e andava a scuola. Poche persone incontrano i buoni genî che hanno sognato, ma Maria, che aveva lavorato sodo e aveva la testa dura e non aveva mai sognato fate, trovò il suo spirito benigno in forma d’un ex-lavandaio. Intanto la gente incominciava a domandarsi: — Ma chi è, dunque, questo Martin Eden? — Egli aveva rifiutata la sua biografia agli editori, ma i giornali non si scoraggiavano per questo. Nella stessa Oakland, i reporters scovarono una quantità di persone capaci di fornire delle notizie preziose, su chi era, e chi non era, tutto ciò che aveva fatto e specialmente ciò che non aveva fatto; tutto ciò fu dimostrato un giorno, pel più vivo godimento del pubblico, e accompagnato da istantanee e da fotografie. Dapprima il suo disgusto per le riviste illustrate e per la società borghese fu tale e tanto, ch’egli tentò di lottare contro la pubblicità; poi, per indolenza, finì col cedere. Pensò che non poteva respingere i corrispondenti che venivano da lontano a trovarlo. Poi, siccome i giorni erano lunghi, ora che non li impiegava per lavorare e scrivere, bisognava pure ammazzare il tempo in un modo qualunque. Cedette a ciò che egli considerava un soffocamento, concesse delle interviste, espresse delle idee sulla letteratura e sulla filosofia, e accettò persino degl’inviti nelle famiglie borghesi. Egli si adagiava in un nuovo stato d’animo strano e comodo; tutto gli era indifferente. Perdonò a tutti, persino al giovane reporter sculacciato che aveva fatto di lui un anarchico militante, e al quale concesse una pagina intera, con fotografia speciale.
- 52. Vedeva di tanto in tanto Lizzie, alla quale dispiacevano le nuove grandezze di Martin, giacchè quegli onori aumentavano la distanza che li separava. Con la speranza di accorciarla, forse, essa si lasciò persuadere a seguire i corsi serali e a farsi fare i vestiti da una grande sarta che si faceva pagare in modo favoloso. Essa faceva progressi di giorno in giorno, al punto che Martin finì col domandarsi se egli faceva bene a comportarsi così, sapendo che tutto ciò che lei faceva, lo faceva con la speranza di piacergli. Essa cercava di acquistar valore agli occhi di lui, d’un genere di valore ch’egli sembrava apprezzare. Eppure, egli non le dava alcuna speranza, la trattava in modo veramente fraterno, e la vedeva di rado. «Troppo tardi» fu lanciato dalla Società Ed. Meredith-Lowell, con la massima popolarità; essendo esso un romanzo, il prezzo di vendita fu molto maggiore di quello de «La Vergogna del Sole». Passavano le settimane, ed egli manteneva il record, senza precedenti, d’avere due libri di gran successo in vetrina, nello stesso tempo, giacchè gli ammiratori de «La Vergogna del Sole», erano ugualmente attratti dall’enciclopedica padronanza con la quale aveva trattato il suo romanzo d’avventure marinaresche. Nell’uno aveva combattuto la letteratura mistica, con rara efficacia; nell’altro aveva svolto con rara facilità i principî ch’egli bandiva, provando così la versatilità del suo genio e rivelandosi, insieme, critico e creatore. Il danaro, la celebrità, affluivano verso di lui; come una cometa egli splendeva nel cielo letterario, e il successo ch’egli creava lo divertiva, più che non lo interessasse. Una cosa sola lo stupiva, — una cosa da nulla. Parecchia gente sarebbe rimasta perplessa, se avesse potuto dubitare del suo stupore: il giudice Blount lo invitò a pranzo! Questo piccolo incidente gli doveva poi diventare una grande cosa nella mente. Egli aveva insultato il giudice, l’aveva maltrattato in modo odioso, e, il giudice, incontratolo per la strada, l’aveva invitato a pranzo!... Martin enumerò le numerose occasioni capitate al giudice Blount in casa dei Morse, per invitarlo a pranzo; allora non l’aveva fatto. Perchè non l’aveva invitato allora? Eppure egli, Martin, non era
- 53. mutato in nulla; era lo stesso Martin Eden. Quale differenza c’era dunque d’allora a ora? Il fatto che le sue opere erano state stampate? Ma le aveva già scritte proprio quando il giudice, seguendo il parere di tutti, rideva delle idee di lui e di Spencer. Dunque, non a causa del suo valore reale, ma a causa d’un valore puramente fittizio, il giudice Blount lo invitava a pranzo! Martin ghignò e accettò l’invito, pur meravigliandosi della sua magnanimità. E a quel pranzo, di cui Martin fu il beniamino, e al quale partecipavano una mezza dozzina di persone altolocate, con le loro mogli, il giudice Blount, caldamente sostenuto dal giudice Hanwell, supplicò Martin di far parte dello «Stige», club ultra-aristocratico, di cui facevano parte non solo i ricchi ma i grandi ingegni. Martin non accettò, e rimase più che mai stupito. I suoi manoscritti partivano l’uno dopo l’altro, tutti; egli era sopraffatto dalle richieste degli editori. Avevano scoperto ch’egli era uno stilista e un pensatore insieme. La Rivista del Nord, dopo aver pubblicato «La Culla della Bellezza», gli aveva chiesto una mezza dozzina di saggi del genere; ed egli l’avrebbe fatto, se il Burton’s Magazine, avido di speculazione, non gliene avesse chiesti cinque, a 2500 lire l’uno. Egli rispose che accettava, ma, ricordando che tutti i manoscritti erano stati rifiutati freddamente, bestialmente, sistematicamente, dalle stesse riviste illustrate che ora l’imploravano, chiedeva 5000 lire per saggio. Essi gli avevano fatto sudare sangue e acqua, un tempo; ora toccava a lui marchiarli a fuoco! E il Burton’s Magazine accettò quel prezzo, e i quattro saggi che rimanevano furono presi, con le stesse condizioni, dal Makintosh’s Monthly, essendo La Rivista del Nord troppo povera per sostenere le spese. Così furono sparsi pel mondo: «I Grandi Sacerdoti del Mistero», «I Cacciatori di chimere», «La misura dell’Io», «La filosofia dell’illusione», «Dio e fango», «L’Arte e la Biologia», «Critiche e prove», «Polvere di stelle» e «La dignità dell’usura», che scatenarono tempeste difficilmente placate. Degli editori gli scrissero pregandolo di fissare egli stesso il compenso, ed egli ciò fece, ma sempre per opere già scritte. Rifiutò
- 54. nettamente di occuparsi di qualsiasi lavoro nuovo; il pensiero di dover mettere del nero sul bianco ancora lo faceva diventar pazzo furioso. Aveva visto Brissenden ridotto a brani dal pubblico, e sebbene non fosse lo stesso per lui, — chè anzi il pubblico lo acclamava, — non s’era ancora rimesso dalla scossa avutane, e non poteva far altro che disprezzare quel pubblico. La sua popolarità gli sembrava un’onta, e un tradimento di fronte a Brissenden. Col disgusto nell’animo, egli decise di seguitare a ingrossare la sua provvista di danaro. Ricevette dagli editori delle lettere così concepite: «Circa un anno fa dovemmo con rincrescimento rifiutare la vostra serie di poemi d’amore: non perchè non ci avessero colpito, ma per impegni già presi che c’impedivano allora d’accettarli. Se li avete ancora, saremmo felicissimi di pubblicarli interi. Fissatene pure il prezzo. Noi saremmo ugualmente dispostissimi a farvi delle offerte molto vantaggiose per raccoglierli in volume da pubblicare». Martin ricordò la sua tragedia in versi liberi e la mandò in vece dei «Poemi d’amore», dopo averla riletta. Gli pareva degna, al massimo, d’un dilettante presuntuoso e senz’alcuna traccia di personalità; ma la mandò, ed essa fu pubblicata, a eterno rimpianto dell’editore. Il pubblico ne fu indignato e stupito; dal nobile talento di Martin Eden a quel pasticcio insipido, c’era un bel divario. Si affermò che egli non l’aveva scritta, che la rivista illustrata l’aveva plagiata in modo molto grossolano, oppure che Martin Eden, plagiando Dumas padre, faceva scrivere le sue opere da un altro, ora ch’era all’apogeo del successo. Ma, quand’egli ebbe spiegato che quella tragedia era un’opera giovanile e che la rivista illustrata aveva implorato per averla, fu un formidabile scoppio di risa a spese della rivista, che fu costretta a licenziare il suo redattore capo. La tragedia non ebbe gli onori della pubblicazione in volume, sebbene Martin avesse già ottenuto gli anticipi concessigli. Poco tempo dopo, Martin ebbe dal Coleman’s Weekly un lungo telegramma di circa 1500 lire, col quale gli si chiedevano venti articoli a 5000 lire l’uno. Doveva viaggiare attraverso gli Stati Uniti, a
- 55. spese del giornale, e scegliere gli argomenti che gli sembravano interessanti in un certo ordine d’idee, di cui gli si dava la lista e senz’altra condizione se non di limitarsi agli Stati Uniti. Martin non accettò e telegrafò, con porto assegnato, il suo rincrescimento. «Wiki-Wiki» pubblicato nel Warren’s Monthly ebbe un successo fulmineo. Apparve subito in un magnifico volume, splendidamente edito e illustrato, le cui copie si vendettero come si trattasse di leccornie. La critica fu concorde nel dichiarare che «Wiki-Wiki» non sfigurava accanto ai capolavori di due grandi scrittori classici: «Il diavoletto nella bottiglia» e «La pelle di zigrino». Il pubblico però accolse la serie dei «Falò di gioia» con alquanta freddezza; l’audacia di queste novelle così assolutamente fuori d’ogni convenzionalismo urtò la morale ed i pregiudizî borghesi; ma quando si seppe che la loro traduzione otteneva a Parigi un folle successo, il pubblico inglese e americano seguì la corrente, e le copie furono vendute in tale quantità, che Martin obbligò la solida Casa Editrice Singletree, Darnley e C. a dargli il venticinque per cento per un terzo libro e il trenta per cento pel quarto. Questi due volumi comprendevano tutte le novelle già pubblicate nelle riviste e nei giornali in corso di pubblicazione. Martin emise un sospiro di sollievo, quand’ebbe fatta la cessione dell’ultimo manoscritto: il castello di verzura e il bel yacht bianco s’avvicinavano a vista. Ebbene! aveva avuto ragione, in fondo, contro il parere di Brissenden, che affermava che nessuna opera di valore poteva aver successo presso le riviste illustrate. Il successo che aveva ottenuto dimostrava il contrario. Eppure, gli sembrava confusamente che Brissenden avesse ragione, tuttavia. «La Vergogna del Sole» era stata la causa prima del successo, molto più che il resto del suo bagaglio letterario, di cui nessuna rivista aveva voluto mai sapere. Senza «La Vergogna del Sole», egli sarebbe rimasto ignoto: e c’era voluto un vero miracolo perchè «La Vergogna del Sole» ottenesse tanto. Singletree, Darnley e C.º erano là ad attestarlo: essi ne avevano dapprima fatto un’edizione di 1500 copie, dubitando di poterla smerciare. La loro esperienza era notoria, ed essi erano rimasti confusi dal trionfo che n’era seguìto. Eppure il
- 56. successo c’era, e indiscutibile, per un colpo di fortuna unico, misterioso. Così ragionando, Martin giunse a dubitare del valore della sua popolarità. Era la borghesia che gli comperava i libri, gli riempiva d’oro le tasche; ora, da quanto egli sapeva di essa, gli sembrava difficile affermare ch’essa potesse apprezzare e comprendere quella specie di letteratura. La bellezza intrinseca, la potenza delle sue opere non esistevano per le centinaia di migliaia di persone che l’acclamavano. Egli non era che il capriccio dell’ora, l’avventuriero che s’era intrufolato nel Parnaso durante il sonno degli Dei. La folla lo leggeva, lo portava alle stelle, con la stupida incomprensione con la quale aveva sbranato «Effimero» di Brissenden. La torma dei lupi lo leccava, anzichè sgozzarlo, ecco; era questione di fortuna. Una cosa sola rimaneva evidente: «Effimero» superava di molto tutto ciò che egli aveva scritto e tutto ciò che avrebbe potuto mai scrivere... Era dunque quello proprio un misero tributo che la canaglia gli pagava, giacchè la stessa canaglia aveva annegato «Effimero» nel fango. Emise perciò un profondo respiro di viva soddisfazione, felice che il suo ultimo manoscritto fosse venduto, vedendo così avvicinarsi il momento in cui tutto sarebbe finito.
- 57. CAPITOLO XLIII. Un giorno il signor Morse incontrò Martin al bureau dell’Hôtel Metropole. Martin non riuscì a capire chiaramente se Morse si trovasse là casualmente, per affari, o se fosse andato con lo scopo d’invitarlo a pranzo; ma inclinò verso questa seconda ipotesi. Il certo era questo: ch’egli era invitato a pranzo dal signor Morse, padre di Ruth, che gli aveva proibito di andare a casa, e aveva rotto il fidanzamento. Martin non risentì alcuna collera, nè si rivestì della sua dignità; si chiese, semplicemente, perchè il signor Morse s’abbassasse così, e se ne sentisse l’umiliazione. E non rifiutò l’invito, ma rimandò la cosa a tempo indeterminato, chiedendo notizie della famiglia, e di Ruth, particolarmente. Il nome di lei gli venne alle labbra naturalmente, senza esitazione; e rimase persino sorpreso di non risentirne la più piccola stretta al cuore. Martin ebbe molti inviti a pranzo, alcuni dei quali accettò; c’era della gente che si faceva presentare a lui, per avere il piacere d’invitarlo. Ed egli continuò ad essere impacciato di quell’inerzia che diventava una cosa grave. Fu invitato a pranzo da Bernardo Higgingbotham, e la cosa lo impacciò maggiormente. Ricordò i suoi giorni di miseria disperata, quando nessuno l’invitava a pranzo; allora ne avrebbe avuto bisogno, quando il bisogno era estremo, ed egli correva rischio di crepare... Paradosso ridicolo! Quando aveva fame nessuno gli dava da mangiare; ora che poteva satollarsi a piacere, i pranzi affluivano da ogni parte. Perchè? Che cosa aveva fatto per giustificare quel cambiamento? Egli era quello di prima. Il signor Morse e sua moglie l’avevano condannato come fannullone, incapace, e per mezzo di Ruth, gli avevano offerto un posto di commesso in uno studio. I suoi meriti li conoscevano giacchè Ruth
- 58. aveva fatto leggere loro i manoscritti, da allora; erano gli stessi, precisamente quelli che, dopo, avevano fatto il suo nome celebre. Dunque, quella celebrità gli aveva procurato gl’inviti a casa loro. Una cosa, intanto, era evidente: i Morse non si curavano nè di lui, nè delle sue opere, ma si sentivano attratti dal suo trionfo attuale e — perchè no? — dall’aureola delle cinque o seicentomila lire. In questo modo la società apprezza gli uomini!... Perchè la cosa doveva essere diversa per Martin? Ma tale trasformazione ripugnava al suo orgoglio; egli voleva essere apprezzato per se stesso; pel suo lavoro, che non era che l’espressione del suo io. Lizzie, lo amava per lui stesso; agli occhi di lei la sua opera non contava. Jimmy il piombatore, tutti i suoi compagni d’un tempo, lo amavano per lui stesso. Gliene avevano dato la prova parecchie volte, dal tempo in cui egli era uno dei loro; gliene avevano dato la prova ancora una volta, in quella famosa domenica a Shell Mound Park. Poco importava ad essi della sua opera!... Colui ch’essi amavano, colui che difendevano di fronte a tutti e contro tutti era Martin Eden, semplicemente, cioè il loro compagno, un bravo ragazzo. C’era anche Ruth: che lei lo avesse amato per lui stesso, era indiscutibile; eppure essa aveva preferito a lui la sua angusta morale borghese. Essa aveva osteggiato le opere letterarie di Martin, specialmente perchè — a quanto diceva — non gli procuravano denaro. Del «Ciclo d’Amore» non aveva saputo dir altro. Anche lei lo aveva supplicato di «formarsi una posizione»! Egli le aveva letto tutto ciò che aveva scritto: poemi, saggi, novelle, «Wiki-Wiki», «La Vergogna del Sole», tutto. E sempre, ostinatamente, lei lo aveva esortato a diventar «serio», a trovare «un’occupazione»! Gran Dio! come se non avesse lavorato, privandosi persino del sonno e del cibo, lavorato sino a morirne, per innalzarsi sino a lei!... E quell’inerzia seguitava a ingrandire. Egli godeva buona salute, mangiava bene, dormiva bene, eppure quell’inerzia diventava un’ossessione. «Ero lo stesso»: questo pensiero gli assillava il cervello. Una domenica, a pranzo, seduto dirimpetto a Bernardo
- 59. Higgingbotham, egli dovette fare uno sforzo per non urlare: — Sono quello di prima! Ed ora mi rimpinzate, e allora m’avete lasciato morir di fame, m’avete chiuso in faccia la porta della vostra casa, m’avete rinnegato, perchè non volevo «cercare un’occupazione». Ero lo stesso, e tutto ciò che ho fatto era già fatto. Ora, v’interrompete rispettosamente quando parlo io, mi ascoltate con la massima attenzione, ammirate sperticatamente le minime parole che io pronunzio. Vi dico che il vostro partito è putrido, e voi, anzichè adirarvi, fate «hum» e «ah!» e riconoscete che c’è molto di vero in ciò che affermo. E perchè? Non già perchè io sia Martin Eden, un buon ragazzo, non totalmente idiota, ma perchè sono celebre, perchè ho del danaro, molto danaro. Se vi dicessi che la luna è un formaggio verde, applaudireste, o, perlomeno, non osereste contraddirmi, perchè sono ricco. E io sono lo stesso d’allora, quando mi facevate rotolare nel fango, sotto i vostri piedi. Ma Martin si trattenne; questi pensieri gli rodevano il cervello senza tregua, ma egli sorrise e riuscì a nascondere la tensione dei suoi nervi. Poichè taceva, Bernardo Higgingbotham tenne lui conversazione, e non l’abbandonò. Egli era un «self-made man», e sentiva tutto l’orgoglio di esserlo; nessuno lo aveva mai aiutato; egli non doveva niente a nessuno, e adempiva i suoi doveri di cittadino e di capo d’una numerosa famiglia. La casa Higgingbotham era il monumento della sua capacità e del suo indefesso lavoro. Egli sentiva per la casa Higgingbotham quella tenerezza che altri provano per la moglie. Ed egli aprì il suo cuore a Martin, rivelandogli la somma di intelligenza e di perseveranza ch’era occorsa per fondar la ditta. Egli aveva anche dei disegni ambiziosi; il quartiere diventava sempre più popoloso, e il negozio era veramente troppo piccolo; se ci fosse stato più spazio, egli avrebbe aggiunto una ventina di miglioramenti che avrebbero fatto guadagnar tempo e danaro. E un giorno lo avrebbe fatto. Tutti i suoi sforzi tendevano a questo scopo: avere il necessario per comperare il terreno confinante e farvi un altro edifizio di due piani. Avrebbe affittato il piano superiore, e i pianterreni dei due edifizî sarebbero stati uniti al negozio
- 60. Higgingbotham. Gli occhi gli lucevano, quando egli parlò delle vetrine nuove che avrebbero compreso il tutto. Martin ad un certo punto non ascoltò più; l’incessante ritornello; «Ero quello di prima», che gli assillava il cervello sopraffaceva la verbosità dell’altro. Questo ritornello lo rendeva pazzo, ed egli cercò di sottrarglisi. — Quanto vi potrà costare? — domandò egli ad un tratto. Suo cognato s’interruppe nel bel mezzo del discorso circa la quantità d’affari che facevano i negozianti del quartiere. Egli non aveva detto quanto gli sarebbe costato tutto ciò, ma lo sapeva, avendolo calcolato tante volte. — Dato il costo del materiale, oggi, — disse, — si potrebbe farlo con ventimila lire. — Compresa la mostra? — Non l’ho contata; ma, costrutta la casa, verrà da sè. — E il terreno? — Quindicimila lire. Egli si chinò avanti, mordicchiandosi nervosamente le labbra, aprendo e chiudendo macchinalmente le mani, mentre Martin scriveva uno chèque, che gli porse poi: era di trentacinquemila lire. — Io... io non posso dare più del sei per cento. — disse l’altro con voce sorda. Martin ebbe voglia di ridere, ma domandò semplicemente: — Quanto verrebbe ad essere? — Aspettate! al sei per cento, sono duemilacento lire. — Un po’ più di settantacinque lire al mese, non è vero? Higgingbotham fece un segno di assenso. — Allora, se non trovate difficoltà, possiamo accomodare la faccenda così (e lanciò uno sguardo a Geltrude): io vi lascio gl’interessi, col
- 61. patto che spendiate queste settantacinque lire al mese per la biancheria, la cura della casa e la cucina. Queste trentacinquemila lire sono vostre, se v’impegnate a permettere a Geltrude di riposare. Accettate? Il signor Higginbotham aveva la gola contratta; il pensiero che sua moglie non si curasse più delle faccende domestiche riempiva d’amarezza la sua anima sordida. Quel dono magnifico indorava una pillola che non voleva andar giù. Sua moglie non avrebbe lavorato più! C’era da arrabbiarsi. — Benissimo! allora, — fece Martin, — pagherò io le settantacinque lire al mese, e... Egli fece l’atto di riprendersi lo chèque, ma Bernardo Higginbotham se ne impadronì precipitosamente, esclamando: — Accetto, accetto! Quando Martin prese il tranvai, era stanco da piangerne. Egli alzò gli occhi verso l’insegna del negoziante. — Maiale! — borbottò. — Oh! che maiale! che maiale! Allorchè il Macintosh’s Magazine pubblicò la «Chiromante», adorna d’illustrazioni di Berthier e di due incisioni di Wenn, Hermann von Schmidt dimenticò d’aver considerato quei versi come osceni, e gridò a tutti i cantoni che erano stati ispirati da sua moglie, fece in modo da farlo sapere a un cronista e si lasciò intervistare da un estroso giornalista accompagnato da un non meno estroso fotografo e da un disegnatore di grido. Ne venne fuori, nel supplemento della domenica, una pagina intera piena di fotografie e di schizzi di Marianna idealizzata, di una folla di particolari intimi di Martin Eden e della sua famiglia e del testo integro della «Chiromante» a grossi caratteri ripubblicata col permesso del Makintosh’s Magazine. La sensazione fu enorme nel quartiere, e delle brave massaie si gonfiarono d’orgoglio perchè avevano relazione colla sorella del grande scrittore, mentre quelle che l’avevano disprezzata sino a quel giorno si affrettarono a rimediare all’errore. Hermann von Schmidt
- 62. rideva sornionamente nella sua botteguccia di riparazioni, e decise di ordinare una nuova insegna. — Sorprendente come rèclame — diss’egli a Marianna. — E non costa un soldo. — Faremmo bene a invitarlo a pranzo, — suggerì Marianna. E Martin andò a pranzo partecipandovi in compagnia di un grasso macellaio in grosso, accompagnato dalla moglie più grassa di lui, gente importante che poteva esser utile all’ambizioso Hermann von Schmidt. C’era voluta l’attrattiva del celebre cognato per deciderli, come anche pel direttore capo delle agenzie per la Costa del Pacifico della bicicletta di marca «Asa», al quale von Schmidt desiderava far piacere per ottenere la rappresentanza di questa marca in Oakland. Insomma, era una buona fortuna avere Martin Eden per cognato, sebbene, nel suo intimo, von Schmidt non potesse capirne la ragione. Nel silenzio delle notti, mentre sua moglie dormiva, egli lottava, lottava con gli scritti di Martin, per giungere alla conclusione che la gente era pazza a comperare quella roba. Da parte sua, Martin capiva sin troppo bene come stavano le cose, mentre, appoggiato allo schienale della sedia, accarezzava con lo sguardo la testa del cognato, sognando di schiacciargli con qualche pugno bene assestato la stupida faccia ghignante di tedesco! Però gli piaceva una cosa in lui: benchè povero e ambizioso, egli aveva preso una serva per risparmiare le grosse faccende alla moglie. Martin conversò col direttore delle agenzie «Asa» e dopo pranzo lo trasse in un angolo, con Hermann, dichiarando che avrebbe assunto l’accomandita del futuro negozio di biciclette e riparazioni di Hermann, che doveva essere il più bello di Oakland. Fece di più, anzi, ed esortò confidenzialmente Hermann a cercare un’agenzia di automobili con garage, giacchè era in condizioni di far prosperare tutt’e due le officine contemporaneamente. Quando si lasciarono, Marianna, con le lacrime agli occhi, gettò le braccia al collo di Martin dicendogli come l’amasse e quanto l’avesse sempre amato. Questo sfogo fu interrotto, è vero, da un silenzio un
- 63. po’ imbarazzante, ch’essa però riempì con nuove lacrime, nuovi baci e con balbettii incoerenti. Martin credette che lo facesse per fargli dimenticare il tempo in cui aveva perduto la fiducia in lui e insistito perchè egli trovasse «un’occupazione». — È incapace di far economia del suo danaro, è evidente, — confidò Hermann von Schmidt a sua moglie. — Quando gli ho parlato d’interessi, sembrava impazzito, e m’ha dichiarato che se gli avessi riparlato della cosa mi avrebbe rotto la mia sporca testa di tedesco. Proprio così: la mia sporca testa di tedesco! Non importa; non è un uomo d’affari, ma è un brav’uomo. Mi dà una gran bella spinta; ed è bello, da parte sua. Gli inviti a pranzo piovvero da tutte le parti, e Martin seguitava a stupirsene. Nel banchetto al Club della Bohème, egli fu il commensale più notevole tra uomini noti di cui aveva sentito parlare tante volte, in vita sua, e che gli raccontarono come, leggendo «L’Appello delle Campane», nella Transcontinental e la «Peri e la Perla», ne la «Vespa», l’avevano immediatamente considerato come vincitore. — Dio mio! e dire che durante quel tempo crepavo di fame e avevo addosso dei cenci! — fece egli tra sè. — Perchè non m’avete invitato a pranzo allora? Era il momento buono. Sono quello d’allora. E nè allora, nè dopo fu detta una parola a proposito de «L’Appello delle Campane» e della «Peri e la Perla». Ma no, ora non m’invitate perchè sono quel che sono; m’invitate perchè tutti gli altri m’invitano, perchè così è la moda. Voi m’invitate ora perchè siete degli stupidi animali, perchè siete la folla, perchè, in questo stesso momento, il cieco e pecorile capriccio della folla vuole accarezzarmi. Ah! come contano poco Martin Eden e l’opera di Martin Eden in tutto questo!... — concluse lui lamentosamente. Poi s’alzò e rispose spiritosamente a un toast spiritoso. E dovunque si trovasse, al Club della stampa, al Club delle Carte o a dei tè poetici, o nelle riunioni letterarie, dovunque, era ricordato «L’Appello delle Campane» e «La Peri e la Perla», e il bene che ne avevano subito pensato. E sempre, Martin si domandava,
- 64. esasperato: — Ma perchè non m’hanno teso la mano? ero lo stesso, «L’Appello delle Campane», «La Peri e la Perla», non hanno cambiato neppure d’una virgola: contenevano altrettanta arte, avevano lo stesso valore. Ma del loro valore e della loro arte, voi ve ne infischiate. Voi ora mi nutrite perchè la folla imbecille si disputa l’onore di nutrirmi. Spesso, allora, vedeva a un tratto apparire, nel bel mezzo della compagnia, un giovinastro con un soprabito troppo corto e un feltro sull’orecchio. Questo gli accadde un pomeriggio, alla società Ebell d’Oakland. S’avviava al palco e avanzava verso il pubblico, quando vide entrare altezzosamente nel salone il giovinastro dal cappello floscio sull’orecchio. Cinquecento donne eleganti si voltarono subito per vedere ciò che Martin fissava con tanta intensità. Esse non videro altro che il passaggio centrale vuoto, ma egli vedeva il robusto giovanotto seguire, ciondolandosi, quel passaggio, e si domandò se quello si sarebbe levato il cappello, sebbene sapesse che non era avvezzo a farlo. Proseguì lungo il passaggio sino in fondo, e salì sul palco. A Martin venne voglia di piangere su quel fantasma della sua giovinezza pensando a tutta la sofferenza alla quale andava incontro; poi, sul palco, andò diritto su Martin e scomparve. Le cinquecento donne applaudirono dolcemente, per incoraggiare il grand’uomo timido che era loro ospite, e Martin, scacciando quella visione dalla mente, sorrise e cominciò la conferenza. Il direttore delle scuole, degno vecchio, fermò Martin per la strada e gli ricordò cordialmente certe scene avvenute nel suo ufficio, dopo le quali Martin venne espulso dalla scuola, per le sue battaglie. — Ho letto il vostro «Appello delle Campane», quando è apparso tempo fa, — disse egli. — È degno di Edgardo Poe. È magnifico! Ho detto leggendolo; — Magnifico!.. E Martin voleva rispondere: — Sì, nei mesi che seguirono, vi ho incontrato due volte e avete fatto finta di non vedermi. Tutt’e due le volte avevo fame, e andavo al Monte di Pietà. Ero lo stesso di oggi, allora. E non m’avete riconosciuto. Perchè mi riconoscete oggi?
- 65. — Dicevo proprio l’altro giorno a mia moglie, — proseguì il degno vecchio, — che sarebbe una buona idea quella di venire a pranzo da noi, una di queste sere. Lei è dello stesso parere mio, dello stesso parere. — A pranzo? — fece Martin, con accento così aggressivo, che l’altro ne sussultò. — Dio mio, sì, sì... a pranzo. Oh! bisognerà contentarsi in casa del vostro vecchio direttore, eh? brigante! — fece egli, nervosamente, con un timido tentativo di frecciata, che voleva essere gioviale. Martin scese la via, con una specie di torpore addosso. Si fermò all’angolo e diede uno sguardo vago in giro. — Vorrei essere dannato, — mormorò, finalmente, — se il vecchio non ha avuto paura di me!
- 66. CAPITOLO XLIV. Un giorno, nella via, la carrozza della signora Morse passò proprio accanto a Martin. Lei salutò sorridendo, egli ricambiò il saluto e il sorriso. L’incidente non lo sorprese punto. Un mese prima, ne sarebbe rimasto disgustato o impacciato e avrebbe cercato di rendersi conto del grado d’incoscienza della signora Morse. Ora, non ci pensò neppure un minuto: lo dimenticò come avrebbe dimenticato la banca centrale o City Hall, dopo essere passato davanti ad esse. Aveva il cervello in subbuglio, con i pensieri che vi giravano senza posa, sempre nello stesso cerchio. Al centro di questo cerchio le parole: «Ero lo stesso» gli rodevano il cervello, come un verme tenace rode un frutto. Le ritrovava svegliandosi, le udiva nei sonni; i più piccoli particolari della vita erano percepiti attraverso quelle parole: «Ero lo stesso»; cosicchè una logica implacabile lo indusse infine a concludere ch’egli non era nulla, assolutamente nulla. Mart Eden, il giovinastro, Mart Eden il marinaio, erano esistiti come tali; ma Martin Eden, il «celebre» scrittore, non esisteva: Martin Eden, il celebre scrittore, era un’illusione creata dall’immaginazione della folla. Ma egli non vi si lasciava prendere: non era quell’idolo che la folla adorava e al quale essa offriva il nutrimento in sacrifizio propiziatorio: egli sapeva il perchè nascosto di ciò. Lesse degli articoli sul suo conto e si stupì davanti ai ritratti nei quali fu incapace di scoprire la minima rassomiglianza con se stesso. Egli era colui che ha vissuto, vibrato, amato; colui il cui carattere mite e tollerante era pieno d’indulgenza per le debolezze della vita; colui che, al suo posto sul castello di prua di qualche nave, aveva navigato verso strani e lontani paesi; oppure colui che, alla testa di una banda di malandrini, aveva lottato in numerose risse. Egli era colui che tante migliaia di
- 67. libri in biblioteca avevano spaventato e fatto indietreggiare la prima volta; e colui che s’era fatto strada tra essi e li aveva conquistati; era colui, infine, che punse con uno sperone la carne nuda per scacciare il sonno e lavorare oltre ogni limite di resistenza umana. Tutto questo era; ma non quella specie d’orco dal mostruoso appetito che il pubblico s’ostinava a voler inghiottire. Alcune cose nelle riviste illustrate lo divertivano, però. Tutti si disputavano la gloria d’averlo lanciato: il Warren’s Monthly annunziò agli abbonati che, essendo sempre in cerca di novità letterarie, era stato esso a presentare, tra gli altri, Martin Eden ai lettori. Il Sorcio Bianco, reclamò la priorità, e lo stesso fecero la Rivista del Nord e il Makintosh’s Magazine; ma il Globo li fece tacere riesumando, dei suoi numeri, quelli che avevano pubblicato i «Poemi del Mare» così vergognosamente straziati. Gioventù e Maturità, risorta senza aver mai pagato i debiti, e letta soltanto da giovani provinciali, reclamò a sua volta. La Transcontinental raccontò in modo degno e convincente come avesse scoperto Martin Eden, prerogativa questa che però le fu contestata con calore da La Vespa, che mostrò a prova «La Peri e la Perla». Nella mischia, i modesti diritti di Singletree, Darnley e C. sparvero interamente. D’altra parte, questa casa che non aveva azioni in nessuna rivista illustrata, non seppe mai rivendicare i suoi diritti. I giornali discussero dei guadagni di Martin Eden: in un modo o in un altro, trapelarono le magnifiche offerte di certe riviste illustrate; dei degni pastori di Oakland gli fecero delle visite amichevoli, e dei pitocchi di professione gli mandarono una valanga di lettere. Ma le donne erano peggiori; le sue fotografie furono disseminate, e degli scrittori s’occuparono della sua persona, descrivendo il suo rude volto abbronzato, sfregiato, le sue larghe spalle, i suoi chiari occhi tranquilli, e i suoi lineamenti emaciati, che definirono ascetici. Egli pensò alla sua giovinezza battagliera, e sorrise. Spesso, tra le donne che incontrava, questa o quella, lo guardava, lo valutava, lo sceglieva.
- 68. Ma egli non faceva che riderne; ricordava la minaccia di Brissenden e rideva di più; le donne non erano un pericolo per lui, di sicuro, avendo superato il tempo critico. Una sera, avendo accompagnato Lizzie alla scuola serale, si vide fissato risolutamente da una donna elegante e graziosa. Quello sguardo era un po’ troppo insistente e prolungato. Lizzie ne capì il significato e si raddrizzò; furiosamente. Martin se ne accorse, come s’era accorto della causa, e le disse che era avvezzo a quelle cose e che se ne infischiava. — Non dovreste infischiarvene! — rispose lei, con gli occhi lucenti di collera. — Non è possibile; voi siete malato! — Non sono stato mai così bene! Peso dieci libbre più d’una volta. — Non parlo del vostro fisico, ma della mente. C’è qualche cosa che non funziona bene, nella vostra macchina mentale. Persino io che sono niente, lo vedo! Egli camminava a fianco di lei, pensoso. — Darei non so che cosa per vedervi liberato da questo malore! — esclamò bruscamente. — Un uomo come voi dovrebbe provar piacere quando si sente guardato così da una donna! Non è naturale. È cosa che va bene per dei ragazzetti, ma voi siete un uomo. E, mi crediate o no, io sarei felice il giorno in cui vi capitasse una donna che vi piacesse. Quand’ebbe lasciato Lizzie alla scuola serale, ritornò difilato al Metropole, e, giunto in camera sua, si lasciò andare su una grande poltrona e si mise a fissare il vuoto, davanti a sè. Non era in dormiveglia, non pensava a nulla: sentiva il cervello vuoto, e non vedeva nulla, se non, di tanto in tanto, delle macchie colorate, luminose che gli formavano delle immagini vaghe sotto le palpebre. Egli le vedeva come in sogno, eppure non dormiva. A un certo punto si raddrizzò e guardò l’ora; erano le otto precise. Egli non aveva nulla da fare, ed era troppo presto per andare a letto. Poi il cervello gli si vuotò nuovamente e altre immagini apparvero, e sparirono sotto le palpebre. Queste immagini erano tutte uguali fra loro;
- 69. rappresentavano sempre delle masse di fogliame e di cespugli attraversati dai raggi ardenti del sole. A un tratto, un colpo alla porta lo fece sussultare. Pensò che si trattasse d’un telegramma, d’una lettera... o fosse la stiratrice che gli portava la biancheria. Poi, gli passò per la mente il ricordo di Joe e si domandò dove potesse essere mai, mentre rispondeva: — Avanti! Pensava ancora o Joe e non si voltò neppure verso la porta, che si richiuse dolcemente. Seguì un lungo silenzio. Avendo dimenticato che avevano bussato, egli s’era immerso nuovamente nel suo torpore, quand’ecco che ode un singhiozzo di donna, un singhiozzo cupo, trattenuto, spasmodico. Allora si voltò e balzò in piedi. — Ruth! — esclamò stupito, sconvolto. Lei stava appoggiata alla porta; aveva il viso pallido e contratto e una mano sul cuore, come per frenarne i battiti. Poi lei tese le braccia verso di lui con aria supplichevole e fece un passo avanti. Egli le prese tutt’e due le mani e sentì ch’erano gelide. Dopo averla accompagnata alla poltrona, ne accostò un’altra e sedette sul bracciale di questa. Era come paralizzato da un profondo impaccio. Nella sua mente, quell’avventura era finita, seppellita; se per un colpo di bacchetta magica, la lavanderia delle Acque Termali di Shelley fosse stata trasportata di botto nell’Hôtel Metropole, presentandogli davanti agli occhi il lavoro di una settimana di stiratura di biancheria, certo non ne sarebbe rimasto annoiato. Parecchie volte fu sul punto di parlare, senza riuscire a trovare la frase adatta. — Nessuno sa che io sono qui, — disse Ruth con voce fioca e con un sorriso supplice. — Che dite? Egli rimase stupito dal suono della propria voce. Lei ripetè la frase.
- 70. — Ah, sì? — disse lui, domandandosi che cosa dire poi. — Vi ho visto entrare e ho aspettato un po’. — Ah, sì? — ripetè lui. In vita sua, non s’era mai sentito così scarso d’idee. — E allora siete entrata, — diss’egli finalmente. Lei fece un piccolo gesto affermativo; i suoi occhi ebbero un lampo maliziosetto, e sciolse la sciarpa che teneva avvolta al collo. — Vi ho visto subito dall’altro lato del marciapiede, quando eravate con quella ragazza. — Sì? — domandò lui semplicemente. — L’accompagnavo alla scuola serale. — Ebbene, non siete contento di rivedermi? — disse lei dopo un nuovo silenzio. — Sì, sì! — fece lui rapidamente. — Ma non avete agito un po’ leggermente, venendo qui? — Nessuno lo sa. Volevo vedervi. Sono venuta per dirvi che sono stata proprio sciocca; sono venuta perchè non ne potevo più, perchè il mio cuore mi spingeva, perchè... perchè avevo bisogno di vivere. — Lei s’alzò, gli si avvicinò, gli posò una mano sulla spalla, un momento, ansante, poi gli scivolò fra le braccia. E poichè sentiva che respingendola le avrebbe inferto la più grave ferita che una donna possa ricevere, egli chiuse le braccia attorno a lei e la tenne stretta contro di lui. Ma in quella stretta non c’era alcun calore, alcun fremito. Lei gli era venuta tra le braccia, ed egli la teneva. Ecco. Lei gli si rannicchiò addosso, poi gli passò le mani attorno al collo e gli cinse la nuca; ma la carne di lui rimase fredda sotto la solita carezza; egli si sentiva sempre più a disagio, estraneo ad ogni conforto. — Perchè tremate così? — le domandò lui. — Sentite freddo? Volete che vi accenda il fuoco? E fece l’atto di svincolarsi; ma lei lo strinse con maggior forza, tremando violentemente.
- 71. — È un po’ di nervosismo, — disse lei battendo i denti. — Fra un minuto passerà. Ecco! mi sento già meglio. I suoi brividi diminuivano a poco a poco. Egli se la teneva sempre fra le braccia, ma la sorpresa e il disagio erano venuti meno. — Mia madre voleva che sposassi Charley Hapgood, — disse lei. — Charley Hapgood! quel grammofono d’idee piatte! — gemette Martin... — Poi aggiunse: — E ora, penso che vostra madre desideri che sposiate me. — Non era una domanda, la sua: era l’affermazione d’una certezza. — Lei non si opporrà più, lo so, — disse Ruth. — Mi considera come un ottimo partito, senza dubbio? Ruth fece segno di sì. — Eppure non sono un fidanzato più conveniente ora, che non quando lei volle rotto il fidanzamento, — disse lui pensoso. — Non sono mutato per nulla; sono lo stesso Martin Eden: no! peggio: fumo più che mai. Non sentite? Senza rispondergli, lei posò le dita sulle labbra di Martin, graziosamente, e attese il bacio che quel gesto le procurava, un tempo. Ma il bacio non venne. Martin aspettò che lei avesse ritirato le sue dita, e proseguì: — Io non sono mutato: non ho «un’occupazione», non ne cerco, non ne cercherò. E ho sempre la convinzione che Herbert Spencer è un nobile e grande uomo, e che il giudice Blount è un asino calzato e vestito. Ho pranzato da lui l’altra sera, e le mie idee al riguardo hanno avuto una nuova conferma. — Ma non avete accettato l’invito di mio padre, — disse lei con voce di gentile rimprovero. — Toh! lo sapete anche voi? L’aveva mandato vostra madre? Lei tacque.
- 72. — È stata vostra madre: lo pensavo. Penso che sia stata anche lei a mandarvi qui, non è vero? — Nessuno sa che sia venuta, — disse lei protestando, — Credete che mia madre me l’avrebbe permesso? — Essa vi permetterebbe di sposarmi, questo è certo. Lei lanciò un grido: — Oh, Martin! come siete crudele! Non mi avete abbracciata neppure una volta. Siete freddo come un marmo. Pensate a quello che ho osato fare! — Lei lanciò uno sguardo intorno, tremando, ma con una certa curiosità. — Pensate che sono qui, in camera vostra! («Vorrei morire per voi, morire per voi!» La voce di Lizzie cantava ancora al suo orecchio). — Perchè non avete avuto il coraggio di farlo prima? — interrogò egli con voce aspra. — Quando non avevo nulla? Quando morivo di fame? Quando ero nè più nè meno quale sono oggi, lo stesso uomo, lo stesso artista, lo stesso Martin Eden?... Ecco la domanda che io mi rivolgo da parecchi giorni, non riguardo a voi, ma in modo generale. Io non sono mutato, vedete, sebbene l’improvviso apprezzamento del mio valore da parte della gente mi porti continuamente a tranquillizzarmi al riguardo. La mia carne è rimasta la stessa, e così le mie dita e il volto. Io non ho acquistato maggior forza e neppure una qualità di più. Il mio cervello è rimasto tale quale era: non ho neppure inventato più nulla di nuovo in fatto di letteratura e di filosofia. Il mio valore personale è precisamente uguale a quello che era prima, quando nessuno voleva sapere di me. Perchè mi vogliono ora?... Questo mi disorienta. È evidente che non è per me stesso, giacchè sono rimasto quale ero quando non mi volevano: dunque è per una ragione esteriore, per una cosa che non riguarda il mio io. Volete che vi dica che cos’è? La consacrazione del mio talento da parte del pubblico; non altro; e così, tutto il danaro che ho guadagnato e che continuo a guadagnare. E perciò, a causa di questa consacrazione e di questo danaro, oggi mi volete.
- 73. — Voi mi spezzate il cuore, — singhiozzò Ruth. — Sapete che vi amo, che sono venuta perchè vi amo. — Temo che non abbiate capito bene la cosa, — diss’egli con dolcezza. — Voglio dire questo: giacchè mi amate, come va che il vostro amore attuale sia così forte, quando il vostro amore di allora era così debole, debole al punto da respingermi? — Dimenticate tutto ciò e perdonatemi! — esclamò lei ardentemente. — Io non ho mai cessato d’amarvi, ricordatevene! E sono qua, ora, tra le vostre braccia. — Ho paura d’essere un mercante pieno di diffidenza, attento al peso, che si sforza di pesare il vostro amore, e temo d’accorgermi che il peso non è giusto. Essa gli si svincolò dalle braccia, si raddrizzò e lo guardò a lungo, profondamente; fu sul punto di parlare, ma esitò e tacque. — Sentite, vi spiegherò il modo di vedere le cose, — proseguì Martin. — Prima, quando non avevo ricevuto la consacrazione ufficiale, fuori del mio ambiente, nessuno si curava di me. Quando scrivevo i miei libri, nessuno di quelli che lessero i manoscritti, si curò di me; anzi, pareva che mi stimassero meno; pareva davvero che scrivendo commettessi un atto perlomeno scorretto. E tutti mi dicevano; procuratevi il pane! Lei fece un cenno di diniego. — Sì, sì, — disse lui, — tranne voi. Voi mi dicevate: cercatevi un’occupazione! La frase famigliare: procuratevi il pane. — come tante altre parole che ho scritto, — vi urta: è brutale. Io vi rispondo che anche a me sembrava brutale quando tutti me la gettavano in faccia, come si raccomanda la buona condotta a una persona traviata. Ma io divago. La pubblicazione dei miei libri, l’accoglienza avuta dal pubblico, hanno mutato la natura del vostro amore. Voi non volevate sposare quel Martin Eden che era null’altro che Martin Eden; non l’amavate così; oggi, il vostro amore s’è ingigantito, e io non posso non
- 74. concluderne che è cresciuto in proporzione del favore del pubblico che ha consacrato il mio talento. Per voi non si tratta del mio danaro, lo so, benchè sia sicuro che entra nel mutamento ch’è avvenuto nei vostri genitori. Tutto questo, naturalmente, non mi lusinga molto; ma il peggio si è che mi fa dubitare dell’Amore... del divino amore. L’amore è dunque cosa tanto materiale che dev’essere nutrito di rèclame e di popolarità? Pare di sì. È un pensiero che mi ha assillato al punto da farmi diventar quasi pazzo. — Povera cara testa! — E lei stese la mano, gli passò dolcemente le dita tra i capelli. — Lasciate stare tutti questi brutti pensieri. Ricominciamo da capo. Io non ho mai cessato di volervi bene. Sì, ho peccato di debolezza cedendo alla volontà di mia madre; non avrei dovuto farlo, ma vi ho sentito parlare così spesso, con tanta generosità, della fragilità dei poveri esseri umani! Stendetela su di me questa carità... Ho peccato per ignoranza! Perdonatemi!... — Oh, vi perdono! — diss’egli con impazienza. — Veramente non c’è nulla da perdonare; ognuno opera come sa, e non può far di più. Sarebbe come se vi domandassi di perdonarmi di non aver potuto trovare «un’occupazione». — Io credevo di far bene, — protestò Ruth. — Voi lo sapete. Vi avrei amato se non avessi creduto di farlo pel vostro bene? — Bene! ma credendo di far bene, voi volevate distruggere ciò che forma la mia personalità. Sì! (Lei voleva interromperlo, ma egli glielo impedì). Sì, voi avreste distrutto la mia letteratura, il mio avvenire. La mia natura è improntata da realismo, e lo spirito borghese odia il realismo, per vigliaccheria, per paura della vita. Voi avete fatto di tutto per farmi temere la vita; voi mi avreste fatto diventar banale in misura della vostra vita borghese, nella quale tutto è meschino, falso e volgare. Ella fece un gesto di protesta. — La volgarità, — una volgarità cordiale, lo ammetto, — è la base della cultura borghese e delle sue raffinatezze. Come vi ho detto, voi volevate modellarmi a immagine dei vostri, secondo l’ideale della
- 75. vostra classe. (Egli scosse tristemente il capo). E anche in questo momento non comprendete; le mie parole per voi non significano nulla di ciò che cerco di mettervi. Per voi, si tratta di pura fantasia; al massimo, vi disorienta, e vi diverte il fatto che questo giovane selvaggio uscito da un abisso di fango si permetta di giudicare la vostra classe e di considerarla volgare. Essa appoggiò la testa contro la spalla di lui, con stanchezza, e fu scossa da un nuovo tremito nervoso. Poichè rimaneva pensosa, egli proseguì: — E ora, volete ricominciare il nostro amore, volete sposarmi, mi volete. Eppure, ascoltate, se i miei libri non fossero stati segnalati, io sarei rimasto lo stesso!... Ma voi non sareste venuta. Sono tutti questi libri, perdio... — Non bestemmiate, — interruppe lei. Il rimprovero lo fece ridere d’un riso amaro. — Ecco! è proprio così, — diss’egli. — In un momento critico, quando è in rischio ciò che voi credete la felicità della vostra vita, una bestemmia vi fa paura, una bestemmia molto innocente, francamente! Queste parole fecero sentire a Ruth la puerilità della sua esclamazione; ma a lei parve che egli esagerasse e se ne ebbe a male. Seguì un lungo silenzio. Lei rifletteva disperatamente, escogitando il modo di riaverlo, mentre egli pensava disperatamente al suo amore defunto. Egli non l’aveva mai amata veramente, ora lo sapeva; aveva amato una Ruth ideale, una creatura eterea, uscita tutta quanta dalla sua immaginazione, la musa ardente e luminosa dei suoi poemi d’amore; la vera Ruth, quella di tutti i pregiudizî borghesi, segnata dal marchio indelebile della meschinità borghese, quella, non l’aveva mai amata. Essa incominciò a parlare a un tratto: — Io so che c’è molto di vero in ciò che mi dite: io ho paura della vita; non vi ho amato abbastanza; ma ho imparato a capir meglio
- 76. l’amore. Oggi, vi amo come siete diventato, per ciò che siete. Vi amo perciò, per tutto ciò che vi fa diverso da quella che chiamate «la mia classe», e a causa di tutte le vostre credenze che io non comprendo, ma che imparerò a comprendere, lo so. Io farò di tutto per comprenderle. Su! fumate, bestemmiate; tutto ciò fa parte di voi e mi piacerà per questo. Imparerò, vedrete! In dieci minuti ho già appreso molto. Il fatto che mi sono arrischiata a venire sin qui è una prova di ciò che ho già appreso. Oh, Martin!... — Essa gli si strinse addosso singhiozzando. Per la prima volta le braccia di lui la cinsero con tenerezza, e lei lo ringraziò con un sorriso felice. — Troppo tardi! — diss’egli. La frase di Lizzie gli tornò in monte. — Sono malato — oh, non fisicamente!... ma la mia anima, il cervello sono malati. Ho perduto il gusto di vivere. Tutto per me è lo stesso. Se m’aveste detto questo pochi mesi fa, la cosa sarebbe stata diversa. Ora è troppo tardi. — Non è troppo tardi! — esclamò lei. — Vedrete! Vi proverò che il mio amore è ingrandito, che tengo più ad esso che alla «mia classe» e a tutto ciò che mi è caro! Io metto sotto i piedi tutti i pregiudizî; la vita non mi fa più paura. Io abbandonerò mio padre e mia madre, e i miei amici non oseranno più pronunciare il mio nome. Se volete, sono vostra, da ora, felice e orgogliosa di essere la vostra amante. Se ho tradito l’amore, voglio ora, per amor dell’Amore, tradire tutto ciò che me l’aveva fatto rinnegare. Lei si alzò, stette davanti a lui, radiosa. — Aspetto, Martin... — mormorò. — Aspetto che voi mi vogliate. Guardatemi. Egli la guardò. La vide splendida. Essa riscattava davvero la sua condotta passata, si mostrava finalmente una vera donna, superiore alle leggi di ferro delle convenzioni borghesi. Era splendida, magnifica, sublime. Eppure... che gli succedeva dunque? Ciò che lei faceva non lo toccava nè lo commoveva; egli l’apprezzava freddamente, l’ammirava cerebralmente; ma il suo cuore non aveva
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