![6 P. K. Patowari et al.
Table 1 Comparison of data from drilling of different materials using µEDM
S. No. Material Tool Optimum
responses
Process parameters
Cap
(pF)
Vol
(V)
FR
(µm/s)
TRS
(rpm)
1 [1] Brass
(40 µm)
Tungsten
(485 µm)
MT = 54 s 104 180 20 1500
OCen = 10 µm 33 75 10 0
2 [2] Titanium
(0.7 mm)
Tungsten
(518 µm)
MT = 583 s 104 145 15 1000
OCen =
45.85 µm
104 75 15 1500
OCex = 2.55 µm 104 75 15 1500
3 [3] Titanium
(0.7 mm)
Tungsten
(518 µm)
MT = 510 s 104 180 15 1000
OCen = 14.7 µm 102 180 5 500
OCex = 2.45 µm 102 180 10 1500
4 [4] Silicon Tungsten
(518 µm)
MRR =
8.15 µm3/min
104 200 10 0
OCen = 15 µm 102 140 10 0
OCex = 13 µm 102 140 10 0
TA = 1.145º 102 140 10 0
CEen = 7.5 µm 102 140 10 0
CEen = 5 µm 103 140 10 0
5 [4] German
silver
Tungsten
(518 µm)
MRR =
124.8 µm3/min
104 200 10 0
OCen = 28 µm 102 140 10 0
OCex = 15 µm 102 140 10 0
TA = 0.515º 102 140 10 0
CEen = 7 µm 102 140 10 0
CEen = 2 µm 102 140 10 0
6 [5] Stainless
steel
(30 µm)
Tungsten
(518 µm)
MT = 229 s 103 145 5 1500
OCen =
38.07 µm
33 75 5 500
CEen = 6.50 µm 33 75 5 1500
7 [6] Metallic
glass
(20 µm)
Tungsten
(513 µm)
MT = 2.14 min 104 100 10 1000
OCen = 7 µm 102 75 10 0
OCex = 5.25 µm 102 75 10 0
TA = 4.29º 33 150 10 0
Cap capacitance; Vol voltage; MRR material removal rate](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-24-320.jpg)
![8 P. K. Patowari et al.
Fig. 4 Schematic of wire
movement path to fabricate a
square array of micro-fin
a first cut, b second cut after
90° rotation of the workpiece
(any direction)
pulse energy is generally high in comparison with µEDM but less than the die-
sinking EDM. To create microfeatures using such wire-cut EDM, the parametric
conditions have to be tuned properly. Debnath and Patowari [7] identified optimum
parametric combination (lower pulse energy, duration and wire feed) to machine
microfeatures with the desired accuracy. Different types of microfeatures have been
successfullymachinedusingthewire-cutEDM,whichiselaboratedinthesubsequent
sub-sections.
Micro-fins. Fins are attached to a hot body to increase the rate of heat transfer.
Generally available fins are in macroscale, but micro-fins are very difficult to fabricate
due to their delicate nature. Researches revealed micro-fins of different profiles have
higher heat transfer rate than that of the macro-fins. The complete machining process
has been accomplished utilizing multiple cuts (two or more) at different orientations
of the workpiece. A computer numerical control code needs to be developed to define
the wire path during machining. A schematic diagram for machining arrays of micro-
fins is displayed in Fig. 4. After completing both the cuts, square extruded micro-fins
have been fabricated. A typical image of the fabricated sample is shown in Fig. 5.
The cross-sectional area of the chosen workpiece is 10 mm × 10 mm, and on that
sample, total 25 × 25 (=625) micro-square fins have been fabricated. The average
size of the generated fins is 165 µm × 165 µm × 800 µm. This type of micro-fins can
also be used as a tool for drilling multiple holes of different shapes at a time. These
tools help in faster production rate and also reduce the defects due to repeatability
of the machining axis.
Similar to the machining procedure of square micro-fins, micro-fins of different
profiles are also successfully fabricated using wire-cut EDM. Figure 6 shows the
schematic wire path movement to fabricate ‘Y’ type of micro-fins, whereas Fig. 7
shows the actual image of the machined micro-fins by wire-cut EDM.
Micro-screws. Screws are one of the most important engineering elements used
in assembling various components in the form of a temporary joint. Generally,
machining is the prime fabrication process to make screws of different profiles and
shapes, but the time consumed is very high. Nowadays, using a sliding die, smaller](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-26-320.jpg)
![10 P. K. Patowari et al.
rolled screws of limited shapes are also fabricated. The rolling process deforms
the metal to form a screw shape, and for this reason, the metals which are easy to
deform are only used. But to fabricate screws with tough metals, the rolling process
faces difficulty, and thus, fabrication of micro-screws from such material is quite a
challenging task. Wire-cut EDM can be used to machine such metals with greater
accuracy, and to fabricate micro-screw, a separate attachment is required to rotate
the workpiece with variable speed [8].
To make a micro-screw using wire-cut EDM, initially turning operation is
performed to reduce the eccentricity of the rotating workpiece and also to get the
near-net dimension of the desired micro-screw. Thereafter, the thread cutting opera-
tion yields the final shape of micro-screw. During turning, the workpiece rotational
speed needs to be high keeping very low feed, whereas, in case of thread cutting, the
workpiece rotational speed has to be minimum with higher feed. Figure 8 shows the
concept for turning and thread cutting operation used for fabrication of micro-screw
in wire-cut EDM. Figure 9 shows the actual image of the fabricated micro-screws of
two different types (one is with head and another one is without head) with a dedicated
notch to drive the micro-screws inwards or outwards based on the requirement.
Fig. 8 Steps for fabricating
micro-screw a turning
operation b thread cutting
operation
Fig. 9 Images of the fabricated micro-screws a visual observation of the fabricated screws
b microscopic image of the trunk c head of the micro-screw](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-28-320.jpg)
![Proficiency of Electrical Discharge Machining … 11
3.3 Block Electrical Discharge Grinding
BEDGistheprocessofusingasacrificialblockinreducingthediameterofcylindrical
rods. The sacrificial block acts as the tool electrode, whereas the rod is attached to
the spindle, which represents the workpiece. The spindle is rotated at a certain speed
and fed against the sacrificial block for sparks to occur. The schematic diagram of
the BEDG process is shown in Fig. 10. BEDG is an effective method for fabrication
of micro-rods, which besides a µEDM setup requires only a flat block of conductive
material. The process suffers a setback in the form of block wear, which instills
dimensional inaccuracy and imprecision in the fabricated micro-rods. Taper (positive
and negative), position shift, overburn and breakage of tooltip are few of the errors
and ill-effects encountered in BEDG process [9]. Holding of the collet, wobbling
effect, block surface taper and higher energy are some of the causes of the errors.
However, these errors can be eliminated to some extent by proper clamping of the
rod in the collet, checking the block clamping and properly choosing the discharge
energy to be used while machining.
Brass micro-rods have been successfully fabricated using the BEDG process,
wherein a brass block is used as the sacrificial tool electrode [10]. It has been found
that feed rate (FR) beyond 2.5 µm/s is detrimental to efficiency as well as the accuracy
of the fabricated micro-rods. Higher TRS yields lower MT and standard deviation
in diameter (SDD) but increases the average diameter (AD) due to increased block
wear. Figure 11 shows a micro-rod fabricated by BEDG process at FR of 2.5 µm/s
and TRS of 1250 rpm, where AD and SDD of 390.12 and 9.86 µm, respectively, are
attained. Elsewhere, the effect of discharge energy on material removal rate (MRR)
is a well-established fact, where MRR increases with an increase in discharge energy
due to the increased volume of material removal with simultaneous decreased MT
[9].
Fig. 10 Schematic diagram of BEDG process: a lateral feed of workpiece, b wear of sacrificial
block and c machined rod](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-29-320.jpg)
![12 P. K. Patowari et al.
Fig. 11 Microscopic image
of a micro-rod fabricated by
BEDG
3.4 Reverse Electrical Discharge Machining
Reverse micro-electrical discharge machining (R-µEDM) is widely used for the
fabrication of micro-rods and micro-fins which are in the form of circular and rect-
angular cross-sectional in shape. In this process, the workpiece in the form of a bulk
rod is connected through spindle via the positive terminal, whereas the tool in the
form of thin plate sheet with single or array of micro-holes is kept on the table and
connected through the negative terminal. During the machining process, the work-
piece is fed into the tool plate sheet up to a predefined length, which defines or
indicates the fabricated length of the micro-rod as shown in Fig. 12.
Micro-tools in the form of micro-rods with circular cross-sectional area have been
fabricated on tungsten bulk rod, where the diameter of bulk tungsten rod of diam-
eter 800 µm has been reduced to a diameter of 200 µm using R-µEDM process
[11]. An aspect ratio of five has been maintained during the experimentation. It
has been observed that MT reduces with the increase in voltage, capacitance and
FR. Voltage contributes more than the remaining process parameters toward MT
and SDD. Surface roughness (Ra) of the machined micro-rods ranges from 2.12 to
5.94 µm, wherein lower capacitance yields lower Ra as compared to higher capac-
itance. Finally, a micro-tool with an aspect ratio of 18 (diameter 170 µm) has been
successfully fabricated using the process.
Fig. 12 Schematic diagram
of R-µEDM a initial bulk
rod b fabricated micro-rod](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-30-320.jpg)
![Proficiency of Electrical Discharge Machining … 13
Fig. 13 Diagram of micro-rod a schematic of initial bulk rod b schematic of fabricated micro-rods
c SEM image of fabricated micro-rods
Arrayed micro-rods have also been successfully fabricated on a brass bulk rod
by R-µEDM process. Brass rod of diameter 1.8 mm has been considered as the
initial workpiece. An array of 2 × 2 micro-tools has been fabricated through the
machining of a bulk rod as shown in Fig. 13. It has been observed that the tool
wear affects dimensions of the arrayed micro-tools during the machining process.
An analytical model has been developed for evaluating the amount of tool wear and
material removal from the workpiece. Tool wear and material removal increase with
the increase in voltage and capacitance. It has been observed that straight micro-rod
with longer length can be fabricated at lower parametric condition [12].
In another work, dimensional variation, MT and erosion rate have been analyzed
while fabrication of micro-rods using R-µEDM. It is observed that as compared to the
tip and root, the middle portion of the micro-rods undergoes lesser dimensional error
[13]. Moreover, an array of 4 × 4 (=16) micro-rods has been fabricated successfully
with each fabricated micro-rod having diameter 58 µm and length 830 µm as shown
in Fig. 14.
3.5 Milling Electrical Discharge Machining
Milling EDM uses the lateral movement of tool and workpiece in the EDM envi-
ronment to machine 3D cavities. The material removal mechanism is identical to
drilling but with an additional feed in the lateral direction (x-y movement). Essen-
tially, the tool feed takes place in two stages, i.e., initially, a rotating tool is fed to a
certain depth in the z-direction (similar to drilling) followed by a horizontal feed of
tool/workpiece to perform machining of the desired slot. It is capable of machining](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-31-320.jpg)
![14 P. K. Patowari et al.
Fig. 14 Machining of
arrayed micro-tools
a micro-tool fabricated by
BEDG process b array of
micro-hole drilled using the
fabricated micro-tool
c condition of micro-tool
after drilling micro-holes
d arrayed micro-tools
fabricated by R-µEDM on
tungsten rod [13]
complex 3D cavities with a simple cylindrical rotating tool. Thus, the process erad-
icates the use of structured tool as in the case of die-sinking EDM in the fabrication
of 3D cavities. But the effect of tool wear in milling EDM is more as compared to
the die-sinking approach as it possesses horizontal (x-y) feed along with the z feed.
A schematic diagram showing the effect of tool wear in the machined surface profile
is displayed in Fig. 15. The surface profile inequality at the end side of the slot as
Machining length
Machining direction
Depth
of
cut
Machined
surface profile
Original
surface profile
Workpiece
Initial tool
electrode
Spark gap
Tool at the end of
machining a layer
Tool
wear
Fig. 15 Schematic of EDM milling showing effect of tool wear](https://image.slidesharecdn.com/85631-250424033011-81942315/85/Advances-in-Manufacturing-Processes-Select-Proceedings-of-RAM-2020-Harshit-K-Dave-32-320.jpg)
Advances in Manufacturing Processes Select Proceedings of RAM 2020 Harshit K. Dave
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- 4. Lecture Notes in Mechanical Engineering Harshit K. Dave Dumitru Nedelcu Editors Advances in Manufacturing Processes Select Proceedings of RAM 2020
- 5. Lecture Notes in Mechanical Engineering Series Editors Francisco Cavas-Martínez, Departamento de Estructuras, Universidad Politécnica de Cartagena, Cartagena, Murcia, Spain Fakher Chaari, National School of Engineers, University of Sfax, Sfax, Tunisia Francesco Gherardini, Dipartimento di Ingegneria, Università di Modena e Reggio Emilia, Modena, Italy Mohamed Haddar, National School of Engineers of Sfax (ENIS), Sfax, Tunisia Vitalii Ivanov, Department of Manufacturing Engineering Machine and Tools, Sumy State University, Sumy, Ukraine Young W. Kwon, Department of Manufacturing Engineering and Aerospace Engineering, Graduate School of Engineering and Applied Science, Monterey, CA, USA Justyna Trojanowska, Poznan University of Technology, Poznan, Poland
- 6. Lecture Notes in Mechanical Engineering (LNME) publishes the latest develop- ments in Mechanical Engineering—quickly, informally and with high quality. Original research reported in proceedings and post-proceedings represents the core of LNME. Volumes published in LNME embrace all aspects, subfields and new challenges of mechanical engineering. Topics in the series include: • Engineering Design • Machinery and Machine Elements • Mechanical Structures and Stress Analysis • Automotive Engineering • Engine Technology • Aerospace Technology and Astronautics • Nanotechnology and Microengineering • Control, Robotics, Mechatronics • MEMS • Theoretical and Applied Mechanics • Dynamical Systems, Control • Fluid Mechanics • Engineering Thermodynamics, Heat and Mass Transfer • Manufacturing • Precision Engineering, Instrumentation, Measurement • Materials Engineering • Tribology and Surface Technology To submit a proposal or request further information, please contact the Springer Editor of your location: China: Dr. Mengchu Huang at mengchu.huang@springer.com India: Priya Vyas at priya.vyas@springer.com Rest of Asia, Australia, New Zealand: Swati Meherishi at swati.meherishi@springer.com All other countries: Dr. Leontina Di Cecco at Leontina.dicecco@springer.com To submit a proposal for a monograph, please check our Springer Tracts in Mechanical Engineering at http://www.springer.com/series/11693 or contact Leontina.dicecco@springer.com Indexed by SCOPUS. All books published in the series are submitted for consideration in Web of Science. More information about this series at http://www.springer.com/series/11236
- 7. Harshit K. Dave • Dumitru Nedelcu Editors Advances in Manufacturing Processes Select Proceedings of RAM 2020 123
- 8. Editors Harshit K. Dave S. V. National Institute of Technology Surat, India Dumitru Nedelcu Gheorghe Asachi Technical University of Iasi Iasi, Romania ISSN 2195-4356 ISSN 2195-4364 (electronic) Lecture Notes in Mechanical Engineering ISBN 978-981-15-9116-7 ISBN 978-981-15-9117-4 (eBook) https://doi.org/10.1007/978-981-15-9117-4 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore
- 9. RAM 2020 Conference Organizing Committee Chairman Prof. S. R. Gandhi, Director, SVNIT, Surat Organizing Secretaries Dr. Shailendra Kumar, SVNIT, Surat Dr. Harshit K. Dave, SVNIT, Surat Coordinators Dr. Amrut S. Mulay, SVNIT, Surat Dr. Pawan Sharma, SVNIT, Surat Steering Committee Dr. R. V. Rao, SVNIT, Surat Dr. H. K. Raval, SVNIT, Surat Dr. K. P. Desai, SVNIT, Surat Dr. A. A. Shaikh, SVNIT, Surat Dr. T. N. Desai, SVNIT, Surat v
- 10. Programme Committee Dr. D. I. Lalwani, SVNIT, Surat Dr. J. V. Menghani, SVNIT, Surat Dr. Ravi Kant, SVNIT, Surat Dr. Dinesh Singh, SVNIT, Surat Dr. V. D. Kalyankar, SVNIT, Surat Dr. S. N. Pandya, SVNIT, Surat Dr. B. N. Sahoo, SVNIT, Surat Dr. Sumit Khare, SVNIT, Surat Advisory Committee Dr. K. P. Rajurkar, University of Nebraska, USA Dr. Dumitru Nedelcu, University of Iasi, Romania Dr. Chintan Vaishnav, MIT, USA Dr. J. P. Davim, University of Aveiro, Portugal Dr. M. P. Jahan, Miami University, USA Dr. H. M. A. Hussein, Helwan University, Egypt Dr. Andrew Y. C. Nee, NUS, Singapore Dr. Panagiotis Kyratsis, UWM, Greece Dr. R. Balasubramaniam, BARC, Bombay Dr. Suhas Joshi, IIT Bombay Dr. J. Ram Kumar, IIT Kanpur Dr. D. Ravi Kumar, IIT Delhi Dr. P. M. Pandey, IIT Delhi Dr. Anupam Agrawal, IIT, Ropar Dr. A. M. Sidpara, IIT Kharagpur Dr. K. Hariharan, IIT Madras Dr. G. S. Dangayach, MNIT Jaipur Dr. Venu Gopal A., NIT, Warangal Dr. P. K. Patowari, NIT, Silchar Dr. Rajiv Kumar Garg, NIT, Jalandhar Dr. P. C. Tewari, NIT, Kurukshetra Dr. Vishal Sharma, NIT, Jalandhar Dr. H. S. Mali, MNIT Jaipur Dr. Prabhat Ranjan, BARC, Bombay Dr. U. Chandrasekhar, Wipro3d Dr. P. K. Jain, IITDM Jabalpur Dr. R. K. Verma, MMMUT, Gorakhpur vi RAM 2020 Conference Organizing Committee
- 11. List of Reviewers Dr. H. K. Raval, SVNIT, Surat Dr. K. P. Desai, SVNIT, Surat Dr. S. K. Budhwar, SVNIT, Surat Dr. P. K. Patowari, NIT, Silchar Dr. T. N. Desai, SVNIT, Surat Dr. H. K. Dave, SVNIT, Surat Dr. J. V. Menghani, SVNIT, Surat Dr. Dinesh Singh, SVNIT, Surat Dr. M. K. Rathod, SVNIT, Surat Dr. Arati Mulay, CoE, Pune Dr. S. N. Pandya, SVNIT, Surat Dr. A. S. Mulay, SVNIT, Surat Dr. B. N. Sahoo, SVNIT, Surat Dr. Pawan Sharma, SVNIT, Surat Dr. Sudhanshu Kumar, MANIT, Bhopal Dr. Prabhat Ranjan, BARC, Mumbai Dr. Piyush Gohil, MSU, Baroda Dr. V. J. Badheka, PDPU, Gandhinagar Dr. K. P. Mehta, PDPU, Gandhinagar Dr. Vishal John Mathai, AMCoE, Kerala Dr. M. K. Chudasama, GEC, Dahod Dr. Dilip B Jani, GEC, Dahod Dr. Hiesh Panchal, GEC, Patan Dr. M. P. Sutaria, CHARUSAT, Anand Dr. J. D. Patel, MEC, Basna Dr. Ravi Bhatt, CGPIT, Gujarat Dr. Shakil Kagzi, SNPIT, Umrakh Dr. K. D. Maniya, CKPCET, Surat Dr. Abhay Utpat, SVERI, Pandharpur Prof. J. M. Joshi, VGEC, Chandkheda RAM 2020 Conference Organizing Committee vii
- 12. Preface Since 2010, Department of Mechanical Engineering at Sardar Vallabhbhai National Institute of Technology, Surat, has been organizing a series of conferences on “Recent Advances in Manufacturing.” In order to enable the sharing of knowledge in the areas of manufacturing technologies, we have organized six national con- ferences on “Recent Advances in Manufacturing” and now we have planned the International Conference on Recent Advances in Manufacturing (RAM-2020). The conference is organized to bring the academicians, researchers and practicing engineers for sharing their experiences in the field of advance manufacturing. RAM-2020 will provide the opportunity for networking among participant institutes/organizations/industries to systematically confront the challenges in mutual areas of interest to advance manufacturing technology in these areas. The proceedings volumes are published in the Springer series Lecture Notes in Mechanical Engineering in two volumes, viz. Volume 1—Advance Manufacturing Processes and Volume 2—Advance Manufacturing Systems. We also acknowledge the academic support from Prof. Dumitru Nedelcu and Prof. K. P. Rajurkar while editing the volumes 1 and 2, respectively. As the entire world is facing the threat from corona pandemic, the international as well as interstate travel is restricted. However, we have tried our best to carve out a comprehensive schedule, keynote speakers and oral presentations in both online and offline modes, all of which will facilitate stimulating insightful discussions within the research community. In spite of such a pandemic situation, 60 partici- pants have presented their findings and exchanged ideas related to manufacturing domain. We are thankful to the conference organizing committee members, the advisory committee members, the reviewers, the session chairs and the volunteers, without whose generous contributions this conference would not number of presentations and number of participants. ix
- 13. Most of all, we thank the participants for enriching the international conference with their active participation. Surat, India Dr. Shailendra Kumar Dr. Harshit K. Dave Organizing Secretary, RAM-2020 x Preface
- 14. Contents Proficiency of Electrical Discharge Machining in Fabrication of Microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Promod Kumar Patowari, Siddhartha Kar, Tapas Debnath, and Amit Kumar Singh Experimental Study of Effect of Machining Parameters on PMMA in Diamond Turning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Kuldeep A. Mahajan, Raju Pawade, and R. Balasubramaniam A Comparative Study of Electro-discharge Drilling Process Using Solid and Tubular Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Sudhanshu Kumar and Harshit K. Dave Optimization of Process Variables in Plasma Arc Machining of Inconel-718 Alloy Using Taguchi with Grey Relational Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Khushboo Sharma, Jai Kishan Sambharia, and Alok Khatri Optimization of WEDM Process Parameters for Aluminium Metal Matrix Material Al+SiC Using MCDM Methods . . . . . . . . . . . . . . . . . . 59 Jaksan D. Patel and Kalpesh D. Maniya Multiple Parameter Optimization by Wire Electrochemical Discharge Machining Process on Quartz Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Rahul O. Vaishya, Ankit D. Oza, and Anurag Gupta Effect of Process Parameters on Etch Depth of Aluminium Material in Photochemical Machining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Abhay Utpat, N. D. Misal, B. P. Ronge, and B. A. Kamble Quartz Micro-machining Using Wire Electrochemical Spark Machining Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Ankit D. Oza, Abhishek Kumar, Vishvesh Badheka, Aditya Nema, and Manoj Kumar xi
- 15. Stress Relaxation Study of Ultrafine-Grained AA 6061 Alloy Processed Through Combined Constrained Groove Pressing and Cold Rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 K. Changela, K. Hariharan, and R. K. Digavalli Effect of Friction Stir Welding Process Parameters on Tensile Strength and Forming Height of Tailor Welded Blanks . . . . . . . . . . . . . 123 Sumit Patel, Shalin Marathe, Keyur Desai, and Harit Raval A Brief Review on Formability, Wall Thickness Distribution and Surface Roughness of Formed Part in Incremental Sheet Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Kiran R. More, Vikas Sisodia, and Shailendra Kumar Parametric Study of Non-axisymmetric Stretch Flanging Process on AA-6061-T6 Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Sai Dhruthi Killi, Keyur Desai, and Harit Raval Experimental Investigation and Effects of Process Parameters on Forming Time and Forming Accuracy in Incremental Sheet Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Bhavin Desai, Shalin Marathe, Keyur Desai, and Harit Raval Effect of Operating Parameters on Forces During Backward Flow Forming Process for AA6061 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Jaydeep B. Bhatt, Ravi J. Bhatt, Harit K. Raval, and Keyur P. Desai Analysis of TIG-Welded Aluminum Alloys During Single Point Incremental Forming at Different Wall Angles. . . . . . . . . . . . . . . . . . . . 187 M. M. Ghadmode, Arpit R. Patil, B. U. Sonawane, and Amrut Mulay Autogenous TIG Welding of Al-5083-H111 Butt Joint . . . . . . . . . . . . . . 205 Keyurkumar D. Tandel and Jyoti V. Menghani Review on Friction Stir Welding of Polymer to Aluminium Alloys: Process and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Rutvik Ghiya and Vishvesh J. Badheka Effect of Process Parameters on Tensile Strength in FSW of Aluminium and Stainless Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Niraj Kumar, Dhrupal Kotadiya, Vishvesh J. Badheka, and Vijay S. Gadakh Study of Friction Stir Welding on Aerospace Grade ZE41AMg Alloy and Its Comparison with Laser Beam Welding on ZE41AMg Alloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Adithyan Annamalai, T. R. Kishore Babu, S. Karthikeyan, N. Siddharth, and S. Muralidharan xii Contents
- 16. Influence of Layer Thickness, Infill Rate and Orientation on Thermal and Structural Loading of FDM Parts . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Andrei-Danut Mazurchevici, Ramona-Iuliana Popa, Constantin Carausu, Simona-Nicoleta Mazurchevici, and Dumitru Nedelcu Experimental Investigation on Influence of Process Parameters on Mechanical Properties of PETG Parts Made by Fused Deposition Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Soham Teraiya, Swapnil Vyavahare, and Shailendra Kumar Analysis of Compressive Strength of 3D Printed PLA Part . . . . . . . . . . 295 Ashish R. Prajapati, Shilpesh R. Rajpurohit, Naushil H. Patadiya, and Harshit K. Dave An Experimental Study of Influence of Gradient Parameters on Compressive Strength, Stiffness, and Specific Energy Absorption (SEA) of Auxetic Structures Fabricated by FDM . . . . . . . . . . . . . . . . . . 305 Swapnil Vyavahare, Soham Teraiya, and Shailendra Kumar Study on Compression Properties of ABS and FPU Parts Printed Using SLA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Ravi Teja Karumuri, Harshit K. Dave, Shilpesh R. Rajpurohit, and Ashish R. Prajapati Experimental Investigation on Tensile Properties of Nylon Glass Fibre Material Made Using Fused Deposition Modelling Process . . . . . . . . . . 329 Mohit R. Chandravadia and M. K. Chudasama Influence of Inter-Lamellar Spacing of Pearlite Phase on Spheroidized Annealed Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Partha Sarathi Sarkar, Bhavesh Rameshchandra Rana, and Pinkal D. Mistry Review on Banana Fibre-Reinforced Composites . . . . . . . . . . . . . . . . . . 359 Chetan Prakash Chaudhari, Kiran Bhole, and Jayram Gholave Experimental Evaluation of Mechanical Properties of Epoxy Based Composite Material Using Taguchi Method . . . . . . . . . . . . . . . . . 381 Vishal Naranje, Ajay Rajan Sankar, Sachin Salunkhe, and Bhanudas D. Bachchhav Experimental and Simulation Study on Permeability of Hybrid Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 Prasanth Kottapalli, Rahul Narkhede, Harshit K. Dave, Himanshu V. Patel, and Rajesh kumar Verma Contents xiii
- 17. Impact and Flexural Testing of Jute and Flax Fiber Reinforced Composites Fabricated by VARTM Process . . . . . . . . . . . . . . . . . . . . . . 411 Chandresh B. Kumbhani, Harshit K. Dave, and Himanshu V. Patel Influence of Fiber Orientation and Number of Layer on Tensile and Flexural Strength of Carbon Fiber-Reinforced Composites Fabricated by VARTM Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 Himanshu V. Patel, Shripal M. Patel, and Harshit K. Dave xiv Contents
- 18. About the Editors Dr. Harshit K. Dave is currently Associate Professor at the Department of Mechanical Engineering, S. V. National Institute of Technology, Surat, India. His research interests include Additive Manufacturing Processes; 3D printing filaments & raw materials; Unconventional Machining processes; Micro machining processes; Modeling & optimization of machining processes; Robotics & Automation. He has published more than 100 papers in reputed international journals and conferences proceedings. He has successfully carried out several research projects funded by the DST, MHRD, GUJCOST, NPIU, etc. Dr. Dumitru Nedelcu is a Professor at the “Gheorghe Asachi” Technical Univer- sity of Iasi (TUIASI), Romania, Director of TUIASI Doctoral School. He is Manager of Fine Mechanics and Nanotechnology Laboratory, President of ModTech Professional Association, ModTech International Conference and Editor-in-Chief of the International Journal of Modern Manufacturing Technologies and Advanced Engineering Forum. He was a Visiting Professor at TAT, Institute of Engineering, Tokyo, Guest Professor at Osaka University, Japan and Grenoble Institute of Technology, France. He had Erasmus teaching internships in prestigious universities from Poland, Italy and Mexico. In October 2016 he was accepted as Visiting Professor at the Silesian University of Technology, Gliwice, Poland. As far as research is concerned, he coordinated 15 national and international projects as project manager/responsible. He has published more than 180 scientific papers on ISI and BDI journals and international conferences proceedings. xv
- 19. Proficiency of Electrical Discharge Machining in Fabrication of Microstructures Promod Kumar Patowari , Siddhartha Kar , Tapas Debnath , and Amit Kumar Singh 1 Introduction Electrical discharge machining (EDM) is used for precise machining of conduc- tive materials irrespective of their strength and hardness. It removes material by melting and evaporation due to the generation of sparks between the tool and work- piece electrodes. In the EDM process, electrical energy is converted into thermal energy, which is visible in the form of a spark. The electrical sparks generate intense heat energy, which is responsible for the removal of material. A gap exists between the tool and the workpiece, which facilitates the occurrence of spark during the machining process. Thus, the process is contactless and free from the ill-effects of vibration and chatter-related problem which are quite relevant in conventional machining processes. The traditional EDM is mainly used for the machining of dies and molds, where the tip of the tool acts as the negative impression of the machined cavity. Besides, it is also used for machining of parts, complex components, intricate shape components, drilling of micro- or nano-holes, etc. But over the years, the EDM process has been P. K. Patowari (B) · S. Kar · T. Debnath Department of Mechanical Engineering, National Institute of Technology Silchar, P.O. Silchar, Assam 788010, India e-mail: ppatowari@yahoo.com S. Kar e-mail: siddkar.nita@gmail.com T. Debnath e-mail: nit.tapas11@gmail.com A. K. Singh Department of Mechanical Engineering, National Institute of Technology Nagaland, Chumukedima, Dimapur 797103, India e-mail: amit.kumar965@yahoo.com © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 H. K. Dave and D. Nedelcu (eds.), Advances in Manufacturing Processes, Lecture Notes in Mechanical Engineering, https://doi.org/10.1007/978-981-15-9117-4_1 1
- 20. 2 P. K. Patowari et al. successfully applied in different forms which can be termed as variants of EDM. The most commonly used EDM variants are die-sinking, wire-cut, block electrical discharge grinding (BEDG), milling and reverse. All these variants possess unique capabilities of fabricating a different kind of features and structures but with the same machining phenomenon. In this phenomenon, initially, the tool with specific geometry moves toward the workpiece, and resulting sparks are produced in between the tool and the workpiece in the presence of dielectric fluid. The first spark is produced at the location where the minimum distance between the electrodes is identified and breakdown occurs at the minimum resistance point. Subsequently, material is removed from both electrodes, and the discharge point shifts to a new location with the closest distance between the workpiece and tool electrode. EDM is a non-contact machining process devoid of any vibration and chatter- related problems. This unique characteristic enables it to machine microfeatures from all electrically conductive material. But, the dimensional accuracy of machined features is affected by the tool wear, which is inevitable in any EDM variant. Proper selection of process parameters helps in minimizing the tool wear, although it cannot be eliminated. Application of suitable tool wear compensation techniques also augments the chances of achieving dimensional accuracy and precision. But, implementation of any compensation technique requires proper assessment and esti- mation of the tool wear and material removal. Thus, proper evaluation of the dimen- sional features of the machined components is paramount to the implementation of a compensation technique. Given all these factors, the present study demonstrates the capability of several variants of EDM in machining microfeatures and discloses their dimensional features to determine the quality of the machined product. Further, the challenges faced during the fabrication of various microfeatures and the measures taken to overcome those are also presented. The organization of the present work is divided into five sections, and each of the section highlights briefly about the corresponding section. The first section intro- duces EDM with a focus on its background and importance. The second section discusses the differences between macro- and micromachining and their transition. The third section provides the detail information about microstructure fabrication techniques via different variants of EDM, in which the process mechanism and the capabilities of die-sinking EDM, wire-cut EDM, BEDG, reverse EDM (REDM) and milling EDM have been demonstrated. The fourth section delivers information about recent research trends and future scope. The last section provides a conclusion and summarizes the major findings of the study. 2 Macro- to Micromachining Using EDM: A Paradigm Shift The material removal phenomenon in EDM is dependent on the energy discharged in the machining gap existing between tool and workpiece. In EDM, voltage is applied
- 21. Proficiency of Electrical Discharge Machining … 3 in the form of pulses at the alternate interval. During the application of voltage, the formation of spark takes place, which raises the temperature and leads to melting and vaporization of the material. The interruption in voltage supply leads to the formation of pressure shock waves in the machining zone, which ultimately leads to evacuation of material, leaving behind the impression of craters in the workpiece and tool. The full process takes place in the presence of a dielectric medium, which is also flushed in the machining zone to remove the debris. The material removal process takes place without any contact between the tool and the workpiece. This non-contact material removal mechanism of EDM enables the use of softer material such as copper and brass as tool electrode while machining hard and tough materials. In EDM, the material is eroded in the form of craters. The dimension of the craters depends on the discharge energy of the process. At lower discharge energy, the effec- tive unit removal of material is very less, and thus, shallow and tiny craters are formed, whereasthecratersgetwideranddeeperwithanincreaseinthedischargeenergy.This concept has been effectively utilized in micromachining of materials using the EDM process, where the supply of lower discharge energy is paramount to remove material in the micro-level. The ability of EDM in performing micromachining is termed as micro-electrical discharge machining (µEDM). The key differences present in the process mechanism of µEDM as compared to macro-EDM are: Plasma channel diameter: The plasma channel radius is less in µEDM due to the supply of lower discharge energy. The plasma channel diameter expands with an increase in pulse duration, and unlike macro-EDM, it may equal or exceed the diameter of the tool. The expansion rate may vary once the plasma channel exceeds the tool diameter. Electrode heating: In micromachining, the machining dimensions typically range from 1 to 999 µm, which necessitates the use of a micro-tool. The use of micro-tool restricts the quantity of energy supplied per discharge as the tool does not possess significant mass to carry the heat. Viscous force of dielectric on the tool: In µEDM, the dielectric cannot be directly flushed in the machining zone. This is because the tool electrode is more sensitive to the viscous force of dielectric which may lead to deflection or bending of the micro-tool. The absence of process forces (except the viscous force of dielectric) allows fabri- cation of microfeatures with high aspect ratio. A µEDM machine tool possesses the ability to fabricate two-dimensional (2D) and three-dimensional (3D) microfeatures with higher accuracy and precision. The minimization of discharge energy has been possible by the use of resistance capacitance pulse generator, where discharge energy is represented as Eq. (1): Discharge energy = 1 2 × Capacitance × Volatge2 (1) The capacitor stores the energy until discharge initiates, whereas voltage deter- mines the breakdown limit at which the current flows through the inter-electrode
- 22. 4 P. K. Patowari et al. gap. The increase in both capacitance and voltage leads to an increase in discharge energy, which expedites the process of material removal. 3 Microstructures Fabricated Using Different Variants of EDM 3.1 Die-Sinking EDM Die-sinking is the most initial and basic form of EDM technology used mainly for manufacturing of dies/molds. It utilizes the concept of manufacturing of replica objects in large-scale production of micromechanical devices. The tool electrode acts as the positive impression of the desired shape of the product, where the machined cavity on the workpiece reflects the negative image of the tool electrode as depicted in Fig. 1. 3D cavities can be machined by this technique provided the desired pattern of tool electrode is fabricated beforehand. But the fabrication of complex patterned tool is a tedious task which requires some pre-processing techniques for their fabri- cation. The concept of sinking EDM is also utilized for drilling, which uses a simple cylindrical tool for machining micro-holes. To enhance the efficiency, most often rotation motion of the tool is applied during the drilling operation. Incorporation of rotation exhibits centrifugal force and agitation effect in the machining zone, which helps in better flushing of eroded materials. Circularity error (CE) also reduces with the incorporation tool rotation as compared to micro-holes drilled without rotation. But, overcut (OC) increases with the actuation of rotation motion in tool electrode due to the phenomenon of secondary sparking between trapped debris and sidewall of the workpiece. Another significant phenomenon affecting the taper angle (TA) of the drilled hole is the tool wear. The tool wears out in both frontal and corner Fig. 1 Schematic diagram of die-sinking EDM Feed Tool Patterned cavity Workpiece
- 23. Proficiency of Electrical Discharge Machining … 5 Fig. 2 Schematic diagram representing a overcut and taper b circularity error portions, which instills dimensional inaccuracy in the final product. Frontal wear is easily compensated by feeding of tool for sufficiently higher length than the required depth of the micro-hole. But, compensation of corner wear is a very tedious task and cannot be eliminated. However, the process parameters can be chosen in such a way that the effect of corner wear is minimum to achieve higher accuracy and precision in the machined micro-holes. The most common dimensional features to determine the accuracy and preciseness of micro-holes are OC at entry (OCen), OC at exit (OCex), TA and CE, which are schematically depicted in Fig. 2, and their corresponding equations are shown in Eqs. (2), (3), (4) and (5), respectively. OCen = Hole entry diameter − Tool diameter 2 (2) OCex = Hole exit diameter − Tool diameter 2 (3) TA(θ) = tan−1 Entry diameter − Exit diameter 2h (4) CE = Circumscribed circle diameter − Inscribed circle diameter 2 (5) where h represents hole depth. Over the years, µEDM has been successfully used for drilling of materials with various electrical and thermal conductivities. Table 1 shows a comparison of data extracted from the drilling of different materials using µEDM process. The range of parameters varied in each study is different and must not be considered the same for all the materials. EDM possesses the ability to machine materials with different thermal and electrical conductivity. From all the studies, it is perceived that minimum machining time (MT) is attained at higher parametric condition, especially at higher voltage and capacitance. On the contrast, the dimensional features such as OC, CE
- 24. 6 P. K. Patowari et al. Table 1 Comparison of data from drilling of different materials using µEDM S. No. Material Tool Optimum responses Process parameters Cap (pF) Vol (V) FR (µm/s) TRS (rpm) 1 [1] Brass (40 µm) Tungsten (485 µm) MT = 54 s 104 180 20 1500 OCen = 10 µm 33 75 10 0 2 [2] Titanium (0.7 mm) Tungsten (518 µm) MT = 583 s 104 145 15 1000 OCen = 45.85 µm 104 75 15 1500 OCex = 2.55 µm 104 75 15 1500 3 [3] Titanium (0.7 mm) Tungsten (518 µm) MT = 510 s 104 180 15 1000 OCen = 14.7 µm 102 180 5 500 OCex = 2.45 µm 102 180 10 1500 4 [4] Silicon Tungsten (518 µm) MRR = 8.15 µm3/min 104 200 10 0 OCen = 15 µm 102 140 10 0 OCex = 13 µm 102 140 10 0 TA = 1.145º 102 140 10 0 CEen = 7.5 µm 102 140 10 0 CEen = 5 µm 103 140 10 0 5 [4] German silver Tungsten (518 µm) MRR = 124.8 µm3/min 104 200 10 0 OCen = 28 µm 102 140 10 0 OCex = 15 µm 102 140 10 0 TA = 0.515º 102 140 10 0 CEen = 7 µm 102 140 10 0 CEen = 2 µm 102 140 10 0 6 [5] Stainless steel (30 µm) Tungsten (518 µm) MT = 229 s 103 145 5 1500 OCen = 38.07 µm 33 75 5 500 CEen = 6.50 µm 33 75 5 1500 7 [6] Metallic glass (20 µm) Tungsten (513 µm) MT = 2.14 min 104 100 10 1000 OCen = 7 µm 102 75 10 0 OCex = 5.25 µm 102 75 10 0 TA = 4.29º 33 150 10 0 Cap capacitance; Vol voltage; MRR material removal rate
- 25. Proficiency of Electrical Discharge Machining … 7 Fig. 3 Microscopic view of machined hole on different materials a Cu-based bulk metallic glass, b brass, c silicon, d German silver, e stainless steel, f titanium grade 2 alloy and TA are minimum at lower capacitance and voltage. With an increase in voltage and capacitance, the discharge energy increases which consequently increases the spark intensity. High intense spark leads to the formation of bigger and deeper craters, which increases the unit material removal per spark but degrades the surface quality. This phenomenon is responsible for higher efficiency and lower surface quality at higher values of capacitance and voltage. Figure 3 shows microscopic images of micro-holes drilled on different materials such as Cu-based bulk metallic glass, brass, silicon, German silver, stainless steel (SS) and titanium (Ti) grade 2 alloy. The mate- rials possess different physical properties, which further apprehend the usefulness of µEDM in micromachining a wide range of materials. 3.2 Wire-Cut Electrical Discharge Machining Similar to die-sinking EDM, wire-cut EDM is another variant of EDM, which is mainly used to cut metal pieces. In this process, a thin brass or molybdenum wire is used to cut conductive materials irrespective of their other mechanical properties. Generally, two kinds of wire-cut EDM is used (a) consumable wire electrode type (where the wire is being discarded after a single use) and (b) non-consumable wire electrode type (where the wire is being used several times before it needs to be discarded). As wire-cut EDM is mainly used to cut a variety of metal pieces, the
- 26. 8 P. K. Patowari et al. Fig. 4 Schematic of wire movement path to fabricate a square array of micro-fin a first cut, b second cut after 90° rotation of the workpiece (any direction) pulse energy is generally high in comparison with µEDM but less than the die- sinking EDM. To create microfeatures using such wire-cut EDM, the parametric conditions have to be tuned properly. Debnath and Patowari [7] identified optimum parametric combination (lower pulse energy, duration and wire feed) to machine microfeatures with the desired accuracy. Different types of microfeatures have been successfullymachinedusingthewire-cutEDM,whichiselaboratedinthesubsequent sub-sections. Micro-fins. Fins are attached to a hot body to increase the rate of heat transfer. Generally available fins are in macroscale, but micro-fins are very difficult to fabricate due to their delicate nature. Researches revealed micro-fins of different profiles have higher heat transfer rate than that of the macro-fins. The complete machining process has been accomplished utilizing multiple cuts (two or more) at different orientations of the workpiece. A computer numerical control code needs to be developed to define the wire path during machining. A schematic diagram for machining arrays of micro- fins is displayed in Fig. 4. After completing both the cuts, square extruded micro-fins have been fabricated. A typical image of the fabricated sample is shown in Fig. 5. The cross-sectional area of the chosen workpiece is 10 mm × 10 mm, and on that sample, total 25 × 25 (=625) micro-square fins have been fabricated. The average size of the generated fins is 165 µm × 165 µm × 800 µm. This type of micro-fins can also be used as a tool for drilling multiple holes of different shapes at a time. These tools help in faster production rate and also reduce the defects due to repeatability of the machining axis. Similar to the machining procedure of square micro-fins, micro-fins of different profiles are also successfully fabricated using wire-cut EDM. Figure 6 shows the schematic wire path movement to fabricate ‘Y’ type of micro-fins, whereas Fig. 7 shows the actual image of the machined micro-fins by wire-cut EDM. Micro-screws. Screws are one of the most important engineering elements used in assembling various components in the form of a temporary joint. Generally, machining is the prime fabrication process to make screws of different profiles and shapes, but the time consumed is very high. Nowadays, using a sliding die, smaller
- 27. Proficiency of Electrical Discharge Machining … 9 Fig. 5 Fabricated array of square micro-fin on a copper rod (10 mm × 10 mm) Fig. 6 Schematic of wire path for fabricating ‘Y’ type micro-fins a initial cut b final cut Fig. 7 Fabricated ‘Y’ type of micro-fins
- 28. 10 P. K. Patowari et al. rolled screws of limited shapes are also fabricated. The rolling process deforms the metal to form a screw shape, and for this reason, the metals which are easy to deform are only used. But to fabricate screws with tough metals, the rolling process faces difficulty, and thus, fabrication of micro-screws from such material is quite a challenging task. Wire-cut EDM can be used to machine such metals with greater accuracy, and to fabricate micro-screw, a separate attachment is required to rotate the workpiece with variable speed [8]. To make a micro-screw using wire-cut EDM, initially turning operation is performed to reduce the eccentricity of the rotating workpiece and also to get the near-net dimension of the desired micro-screw. Thereafter, the thread cutting opera- tion yields the final shape of micro-screw. During turning, the workpiece rotational speed needs to be high keeping very low feed, whereas, in case of thread cutting, the workpiece rotational speed has to be minimum with higher feed. Figure 8 shows the concept for turning and thread cutting operation used for fabrication of micro-screw in wire-cut EDM. Figure 9 shows the actual image of the fabricated micro-screws of two different types (one is with head and another one is without head) with a dedicated notch to drive the micro-screws inwards or outwards based on the requirement. Fig. 8 Steps for fabricating micro-screw a turning operation b thread cutting operation Fig. 9 Images of the fabricated micro-screws a visual observation of the fabricated screws b microscopic image of the trunk c head of the micro-screw
- 29. Proficiency of Electrical Discharge Machining … 11 3.3 Block Electrical Discharge Grinding BEDGistheprocessofusingasacrificialblockinreducingthediameterofcylindrical rods. The sacrificial block acts as the tool electrode, whereas the rod is attached to the spindle, which represents the workpiece. The spindle is rotated at a certain speed and fed against the sacrificial block for sparks to occur. The schematic diagram of the BEDG process is shown in Fig. 10. BEDG is an effective method for fabrication of micro-rods, which besides a µEDM setup requires only a flat block of conductive material. The process suffers a setback in the form of block wear, which instills dimensional inaccuracy and imprecision in the fabricated micro-rods. Taper (positive and negative), position shift, overburn and breakage of tooltip are few of the errors and ill-effects encountered in BEDG process [9]. Holding of the collet, wobbling effect, block surface taper and higher energy are some of the causes of the errors. However, these errors can be eliminated to some extent by proper clamping of the rod in the collet, checking the block clamping and properly choosing the discharge energy to be used while machining. Brass micro-rods have been successfully fabricated using the BEDG process, wherein a brass block is used as the sacrificial tool electrode [10]. It has been found that feed rate (FR) beyond 2.5 µm/s is detrimental to efficiency as well as the accuracy of the fabricated micro-rods. Higher TRS yields lower MT and standard deviation in diameter (SDD) but increases the average diameter (AD) due to increased block wear. Figure 11 shows a micro-rod fabricated by BEDG process at FR of 2.5 µm/s and TRS of 1250 rpm, where AD and SDD of 390.12 and 9.86 µm, respectively, are attained. Elsewhere, the effect of discharge energy on material removal rate (MRR) is a well-established fact, where MRR increases with an increase in discharge energy due to the increased volume of material removal with simultaneous decreased MT [9]. Fig. 10 Schematic diagram of BEDG process: a lateral feed of workpiece, b wear of sacrificial block and c machined rod
- 30. 12 P. K. Patowari et al. Fig. 11 Microscopic image of a micro-rod fabricated by BEDG 3.4 Reverse Electrical Discharge Machining Reverse micro-electrical discharge machining (R-µEDM) is widely used for the fabrication of micro-rods and micro-fins which are in the form of circular and rect- angular cross-sectional in shape. In this process, the workpiece in the form of a bulk rod is connected through spindle via the positive terminal, whereas the tool in the form of thin plate sheet with single or array of micro-holes is kept on the table and connected through the negative terminal. During the machining process, the work- piece is fed into the tool plate sheet up to a predefined length, which defines or indicates the fabricated length of the micro-rod as shown in Fig. 12. Micro-tools in the form of micro-rods with circular cross-sectional area have been fabricated on tungsten bulk rod, where the diameter of bulk tungsten rod of diam- eter 800 µm has been reduced to a diameter of 200 µm using R-µEDM process [11]. An aspect ratio of five has been maintained during the experimentation. It has been observed that MT reduces with the increase in voltage, capacitance and FR. Voltage contributes more than the remaining process parameters toward MT and SDD. Surface roughness (Ra) of the machined micro-rods ranges from 2.12 to 5.94 µm, wherein lower capacitance yields lower Ra as compared to higher capac- itance. Finally, a micro-tool with an aspect ratio of 18 (diameter 170 µm) has been successfully fabricated using the process. Fig. 12 Schematic diagram of R-µEDM a initial bulk rod b fabricated micro-rod
- 31. Proficiency of Electrical Discharge Machining … 13 Fig. 13 Diagram of micro-rod a schematic of initial bulk rod b schematic of fabricated micro-rods c SEM image of fabricated micro-rods Arrayed micro-rods have also been successfully fabricated on a brass bulk rod by R-µEDM process. Brass rod of diameter 1.8 mm has been considered as the initial workpiece. An array of 2 × 2 micro-tools has been fabricated through the machining of a bulk rod as shown in Fig. 13. It has been observed that the tool wear affects dimensions of the arrayed micro-tools during the machining process. An analytical model has been developed for evaluating the amount of tool wear and material removal from the workpiece. Tool wear and material removal increase with the increase in voltage and capacitance. It has been observed that straight micro-rod with longer length can be fabricated at lower parametric condition [12]. In another work, dimensional variation, MT and erosion rate have been analyzed while fabrication of micro-rods using R-µEDM. It is observed that as compared to the tip and root, the middle portion of the micro-rods undergoes lesser dimensional error [13]. Moreover, an array of 4 × 4 (=16) micro-rods has been fabricated successfully with each fabricated micro-rod having diameter 58 µm and length 830 µm as shown in Fig. 14. 3.5 Milling Electrical Discharge Machining Milling EDM uses the lateral movement of tool and workpiece in the EDM envi- ronment to machine 3D cavities. The material removal mechanism is identical to drilling but with an additional feed in the lateral direction (x-y movement). Essen- tially, the tool feed takes place in two stages, i.e., initially, a rotating tool is fed to a certain depth in the z-direction (similar to drilling) followed by a horizontal feed of tool/workpiece to perform machining of the desired slot. It is capable of machining
- 32. 14 P. K. Patowari et al. Fig. 14 Machining of arrayed micro-tools a micro-tool fabricated by BEDG process b array of micro-hole drilled using the fabricated micro-tool c condition of micro-tool after drilling micro-holes d arrayed micro-tools fabricated by R-µEDM on tungsten rod [13] complex 3D cavities with a simple cylindrical rotating tool. Thus, the process erad- icates the use of structured tool as in the case of die-sinking EDM in the fabrication of 3D cavities. But the effect of tool wear in milling EDM is more as compared to the die-sinking approach as it possesses horizontal (x-y) feed along with the z feed. A schematic diagram showing the effect of tool wear in the machined surface profile is displayed in Fig. 15. The surface profile inequality at the end side of the slot as Machining length Machining direction Depth of cut Machined surface profile Original surface profile Workpiece Initial tool electrode Spark gap Tool at the end of machining a layer Tool wear Fig. 15 Schematic of EDM milling showing effect of tool wear
- 33. Another Random Document on Scribd Without Any Related Topics
- 34. Nao, he said. I wouldn't knaow who done fer John. Dan's upset, Jeff explained. He didn't realize what he was saying. An explosive, I did, too lingered on Dan's lips and died there when he caught Jeff's eyes. As the latter turned to lift his own breakfast out of the skillet, Pete nodded vigorously. Likely. Likely. Young'uns do get upsot. What be ye doin' here? Jeff said smoothly, We represent Tarrant Enterprises, Ltd., and came because we thought we could do some business around Smithville. Pete's shifty eyes found Jeff's pack. Peddler, huh? Some people call it that. Whar'd ye find the dog? Over beyond Cressman. He made himself at home with us. Jeff put his own plate on the table and began to eat. Pete mopped up the last of his breakfast with a crust of bread, plopped it into his mouth, and licked his fingers. That done, he picked up the conversation where it had been dropped. Take care he ain't kil't. Take care who isn't killed? The dog. He turned right snarly after Blazer was kil't. Bill Ellis'd a shot him if he hadn't took a mind to run away. Did he hurt anybody? Nao. But he had a mind to. Pete leaned back, looking at the ceiling and cleaning his teeth with his tongue. He asked suddenly, Whar'd ye get the young'un?
- 35. For a moment Jeff fumbled. But Tarrant Enterprises, Ltd., had taught him that it was not a good idea to be at a loss long enough to let anyone else think too far ahead of him. He said glibly, Dan was farmed out to me. Jeff referred to the common practice of placing with accredited people who would support them, youngsters who had no other place to turn. Dan glared. Jeff did not look at him. Pete Whitney said, You git a smart lot of work out'en a farmed-out young'un if you whomp him to it. Jeff's next words erased Dan's glare. Dan doesn't need 'whomping.' We're full partners. Aoh. There was another silence. Finally Pete Whitney asked, What ye peddlin? What do you need? I ast you. Cash or swap? Swap. Pete looked surprised that anyone should think he had cash. What can you swap? Pete reached inside his shirt and drew out a knife. It was much cruder than the works of art Jeff had had from Bart Whitney. But it was sturdy, and the blade, Jeff thought wryly, was certainly keen enough to penetrate anything that Pete might have reason to stab. Since there was a buyer for everything, it stood to reason that there would be a buyer for Pete's knife. Jeff went to his pack, took out a cheap jackknife, a compass and a wrapped parcel. He extended the knife. I'll swap even for this.
- 36. Pete accepted the knife, opened it, tried the blade on the back of his horny hand, and passed it back. Nao. That piddlin' thin'd bend on rabbit fur. Enjoying himself, as he always did when bartering, Jeff handed the compass over. Pete looked at it. Puzzled, he glanced back at Jeff. Do it tell the hour? Dan laughed. Jeff explained. It's called a compass. See? The needle always points north. Anyone who carries this can tell any direction at all. Pete was honestly astounded. You mean they's some what cain't? There are some, but I thought you wouldn't be one of them! He spoke admiringly, stressing the you. Sales resistance faded to nothing if the seller, while convincing the buyer that he was much to be admired, could at the same time build up the buyer's opinion of himself. Like a good showman, Jeff had saved his masterpiece for last. He unwrapped the parcel to reveal a cheap box whose exterior was stamped with gaudy green dragons. Pete regarded it with narrowed eyes. This, Jeff said smoothly, I offer to very few customers. Now if you'll just keep your eye on the box— Pete obliged, bending so closely that his face was no more than six inches from the box. Jeff pressed a button. The lid flew open and a green bellows surmounted by a grinning clown's head sprang up to hit Pete on the nose. He leaped backward, flung himself from the table and crouched. Again Jeff thought of an animal. But this time it was a beast of prey. And it was ready to strike. The jack that had leaped out of the box quivered on the table, swaying this way and that. Completely astounded, Pete regarded it for a moment. Then sheer delight flooded his eyes.
- 37. I swan! Jeff said proudly, Ever see anything like that? Put it back! Jeff pressed the jack into place. Uncertainly, still a little fearful of such magic, Pete came near. He extended a hand and immediately withdrew it. Do it ag'in! Jeff pressed the button and the performance was repeated. Sure now that there was nothing to fear, Pete picked the toy up and looked at it closely. He pushed the jack down, latched the cover, and pressed the button. When the clown's head flew up, he tittered nervously. I swan! For that I must have two knives. Got but one. Jeff frowned. The jack-in-the-box was a cheap trinket and the knife was worth four times as much. But Pete considered the jack a very valuable object and Jeff hoped to do much trading around Smithville. He did not want to be known for accepting the first thing offered and, besides, that was bad business. It took all the sport out of trading. Have to have something to boot, he said firmly. I got this. From his sagging pocket Pete took a length of braided horsehide. But it had been so skillfully cured and so expertly braided that it was strong as rope and pliable as the finest cloth. It would make a wonderful bridle rein, but Jeff said hesitantly, I don't know what I'd use it for.
- 38. Fer tyin' things. Well— Jeff allowed himself to be convinced. Pete sprung the jack again and again, fascinated by this simple thing which smacked of magic, because never before had he seen anything like it. Then, holding his jack-in-the-box as though it were eggshells, he made the swift transformation from fascinated child to dangerous man. Stick to peddlin', he said shortly, and took his leave. It was at the same time a threat and a warning and Jeff knew it. For a moment he sat still, then got up and strolled quietly to the window. Going down the path, Pete Whitney sprung the jack and his tittering giggle seemed again to be heard in the room.
- 39. 7. GRANNY Absorbed in watching Pete, Jeff was almost unaware when Dan came to stand beside him. As Pete disappeared, hidden by foliage, he turned away from the window and came face to face with Dan. The boy's cheeks were flushed and hot anger burned in his eyes. Both fists were clenched so tightly that straining knuckles showed white. Jeff said quietly, Come out of it, Dan. He's a Whitney! Sorry you didn't shoot him? I—It's not that, Jeff. I wasn't thinking very straight when I told you I aimed to shoot all the Whitneys. It's—Why should a Whitney be in my pop's cabin? He was at our door and he was hungry. Well—Doggonit, Jeff! You talk sense! Jeff heaved an inward sigh of relief. Yesterday Dan had not only talked of killing every Whitney, but he had acted fully capable of doing it. But yesterday he had been tired, hungry and so terribly alone. Good food and proper rest had worked a change, but they had not made him forget why he was here. Nothing would ever do that. Dan asked, You think we will get him, don't you? Get who? Whoever killed my pop!
- 40. Murder can't be hidden, Dan, Jeff spoke with quiet forcefulness, if somebody really wants to find it out. And we'll find out? We'll find out. Then, Dan gritted his teeth, we'll shoot! Jeff said nothing. Dan was too young, too angry, and too steeped in the traditions of the hills, to think of anything except violent vengeance. Rather than tell him he was wrong, Jeff hoped to prove it. When they found whoever had murdered Johnny Blazer—and they must find him if Dan's tangled path was ever to be straight again—the law could take over. Jeff hoped that, at the right time, Dan would see such a course as the proper one. For the present, the less said the better. Let's get the place cleaned up and go out trading, Jeff suggested. Good! Jeff washed dishes while Dan swept the floor, and it made no difference that it had also been swept last night. Only those with little regard for themselves were contented to accept dirty surroundings, and one way to keep dirt from accumulating was to clean often. The cabin in order, Jeff showed Dan his pack. Each of its numerous straps, so adjusted that they opened at the flick of a finger, gave access to one compartment, and within themselves some of the compartments were further divided. They were also of various sizes. Obviously it was possible to carry a vast number of pins, needles, spools of thread, etc., in a somewhat small space. Kitchen ware, of which Jeff had a considerable store, naturally needed more room. There was a place for bright ribbons, one for candy, and articles such as spices and tea were stored by themselves. Jeff had razor blades, pencils, an assortment of novelties such as the jack-in-the-box, a variety of small tools, nails, and both wood and metal screws. At the rear, reached by thrusting
- 41. the hand through a hidden flap, were six more knives like the one he'd traded to Barr Whitney, meerschaum pipes, pocket watches, and a few other valuables that were best kept where they were not at once available or easily found. Jeff explained that he always planned to carry as great an assortment as possible, with very few large articles. The partial bolt of gingham, the biggest single thing in the pack, he carried, not because there was much profit in carrying it, but because being able to offer gingham often provided an opening wedge to other sales.... When he started, he had operated on a strictly cash basis and had earned a fair amount of money doing so. Then he had discovered a great truth which had its foundations in the complexities of human nature. No matter what the article, from aardvark whiskers to zebra tails, somewhere somebody not only wanted it but wanted it badly enough to pay well. On the Atlantic Coast, Jeff had picked up a box of sea shells. In Indiana, he had met a trapper who'd never seen any sea shells and traded them for a bundle of mink pelts. Taking the pelts to Chicago, he had sold them to a furrier for more money than he might have earned in two weeks peddling for cash. Though everything was precious, or at least desirable, to somebody, whoever had an abundance of any kind of goods was seldom inclined to regard it highly. But though they'd always sell for cash, whoever offered something that they wanted, did not have and would find it difficult to get, invariably made a better bargain. Jeff cited the knife and thong he had acquired from Pete Whitney. The jack-in-the-box had cost fifteen cents, but Jeff would be able to sell the knife for at least a dollar and twenty cents, and he did not know how much the horsehide thong would bring. But because Pete thought the jack-in-the-box such a treasure, and never would have been able to get one for himself, he hadn't been cheated. Jeff concluded with the observation that peddlers had to recognize true value when they saw it. Otherwise they would not be able to remain in business.
- 42. Dan's eyes sparkled. That sounds like fun! It has its points, Jeff admitted. Take me in with you for good! Dan pleaded. I want to be a peddler, too! Jeff glanced aside. He had taken this waif under his wing and could not abandon him. Then he was struck by the happy thought that Dan's request gave him control over his charge. We'll see, he evaded the issue. Take me! I'll do anything if you'll teach me! Jeff asked quickly, Can I count on that? Anything! Just ask me! You'll do exactly as I say? Try it! What do you want done? Jeff grinned. Right now let's go peddling—and leave the shotgun here. But— You said you'd do anything. Let's go, Jeff. With an ease born of long experience, Jeff slipped into the pack. Knowing that they were going out, Pal leaped to his feet and a doggy grin framed his jaws. Jeff closed the door but did not lock it. The cabin had been rifled only because it was thought abandoned. Known to be occupied, it was safe. The hill men might use force to get what they wanted, or even kill another man for it, but petty pilfering was beneath them. The sun was warm without being too warm, and a breeze fanned the cheeks of the pair of peddlers. The smile was complete on Jeff's
- 43. face, and laughter was in his heart. The horizon stretched limitlessly, with no end or definition, and good fortune was a certainty. He couldn't be other than happy. Where we going, Jeff? Dan asked. I don't know. Let's follow our noses and go where they lead. Jeff took the first mule and footpath that branched from the road, for he was sure that most of the people he wanted to see would be back in. Most hill people preferred plenty of room and they did not, as one hillbilly had expressed it to Jeff, like to be All cluttered up with people. Skassly a week passes but what three, four go by. Ranging ahead, Pal flushed a buck from its thicket, chased it a little way, and let it go. He returned to Jeff and Dan, lingered to sniff at some interesting rabbit tracks, and ran to catch up. There came a faint smell of wood smoke. Jeff sniffed eagerly, trying to determine the smoke's origin, and he thought with some amusement that he was doing exactly as he had told Dan they would do. In a very real sense he was following his nose, and when he came to a less-traveled path that swung from the one they were following, he took it. Pal at his heels, Dan bringing up the rear, he walked fast. In three minutes they came to a clearing. Apparently without plan, it had been hacked out of the forest. It was irregularly-shaped, probably to follow the easiest cutting, and a few large trees had been allowed to stand in it. There were many stumps, a small garden, a mule that hung its head over the topmost of two strands of rusting wire and looked cynical, and four half-wild pigs that squealed and scuttled into the brush. The barn, that had listed badly and seemed in immediate danger of falling, was propped up with saplings. The house, made of hand-hewn timbers, was very small and very old. Rains, snow, sun and wind had so beaten it that it had achieved a unique color all its own and somehow it looked sad.
- 44. Jeff knocked confidently and waited. The door opened an inch, then another inch, and in the gloomy interior Jeff saw, not too well, a scowling face that was framed in a veritable haystack of black hair and beard. But he saw very clearly the sinister snout of a rifle that was aimed squarely at his middle and he heard very clearly a growled, Git goin' an' start now! Right away, Jeff agreed. He whirled and started back to the main path. Too over-awed to speak, Dan trotted at his heels and he dared say nothing until they were once more where they had started from. Then, Gee! he breathed. Weren't you scared? No, Jeff answered wryly, my heart always pounds. Do you think he didn't want us around? I had a slight suspicion. What do we do now? Find somebody else, Jeff said cheerfully. It's part of peddling. The day was too fine, and too sparkling, to be ruined by any surly mountaineer. They walked on, feet winged and hearts gay. Jeff thought whimsically that the money he made selling or trading was the very smallest part of the reward he received. By far the major portion lay in walks just like this, in the fact that he loved the work he was doing, and in trying to anticipate what lay ahead. He always tried to build up a mental picture of his next customer, always failed to do so, and invariably had to discard his carefully-rehearsed approach to create a new one on the spur of the moment. Much of the time he knew the sort of house in which his next prospect would live, but nothing in his experience had prepared him for the house they found not a mile from the one they had left.
- 45. Rounding a bend, they saw a little hill. There was nothing majestic or imposing about it, for it was a very small hill. But it was a very beautiful one. It was as though the Creator of the mountains, after much deliberation, had decided that the little hill would fit nowhere except exactly where it was. All the trees save one had been stripped from the side, Jeff and Dan could see, and the grass growing there was so green and soft that it was almost unreal. The one tree gave it just the right touch, so it was as though this hill were something out of fairyland. A little herd of sheep cropped the grass. Delighted, Jeff let his gaze stray upward. Gee but it's pretty! Dan breathed. It is that, Jeff agreed. Look at the house. There were trees on the very top of the hill. Silhouetted against the blue sky, they seemed to be outlined against a gentle sea. A log house nestled in the grove. Something—at first Jeff thought it must be the whitewash that outlined all the windows and then he knew it was not—set the house apart. Like the hill, it was a fairyland house and Jeff knew that they must visit there. The hill rose in undulating waves, with no harsh angles or uncouth lines to mar it. But it was not a park-like perfection. Some person, or persons, must have expended enormous labor to make the hill look as it did. But every line, every patch of grass, seemed to belong naturally just where it was. Jeff could decide only that this was a happy hill and that whoever lived in the house was either the owner of a rare talent or blessed beyond belief by the angels. Or perhaps some of both. They came to the house and marveled. It was made of logs and chinked with clay, but nothing haphazard had gone into its making. Even the chinking was not just slapped on and troweled in, but flowed in graceful lines as though it had always been part of the
- 46. logs. As old as the cabin they had left, the house had a sheen instead of a sad and aged appearance. Whoever lived here must love it greatly. Howdy, boys. The woman came around the house so silently and so unexpectedly that for a moment Jeff was startled. The top of her head reached scarcely to his shoulder. Her silver hair glowed like a halo, but there was something which was far from angelic in the remarkable eyes that dominated her unusual face. She wore a simple blue dress. Highlighted in silver, an exquisitely-stitched blue-bird in flight adorned the front of it. Her movements were quick and graceful. But there was no suggestion of frailty, and the muzzle loading rifle that swung easily from her right hand might have been a strong man's weapon. Without any hesitation, Pal went forward to receive her caress. In a sudden rush of feeling, Jeff forgot his amazement and felt entirely at home. He knew all at once that everything and everybody was welcome on this hill. And howdy to you, Granny! he said graciously. I'm— Jeff thought of introducing himself as Tarrant Enterprises, Ltd., but did not. I'm Jeff Tarrant and this is Dan Blazer. Her head flitted like a bird's. And I'm Granny Wilson. Wilson? Jeff remembered. I met an Ike Wilson in Cressman. Did you now? Ike's one of my boys. What was he doin'? He was— Jeff fumbled. Darned if I haven't forgotten! Her laugh was like rippling water. He was in jail for stealin' chickens. You can say it, Jeff. It takes all kinds to make a family. My Tommy's a doctor, my Joel's a lawyer, my Billy's a sailor— She named four more sons, all of whom were in some useful occupation, and finished, They all followed their natural bent and Ike just naturally
- 47. took to chicken stealin'. She turned to Dan. You kin to Johnny Blazer? Dan said bashfully, He was my pop. Come in, she invited. Come in and set down to gingerbread and milk. I vow I've missed Johnny and I'm glad to have his kin! You come, too, Jeff, and fetch your dog! Jeff looked at the rifle. Have you been hunting? Land no! She laughed. I was shootin' at Brant Severance! You—! Didn't hit him, she said. Didn't aim to hit him. Just wanted to show him he couldn't pester my sheep. But—isn't there— She anticipated and forestalled his question. Nope, I'm all alone. My boys, they want me to come with them. Land! I'd grow old and shrively in a city! Two houses are one too many! Do come in. Granny opened the door that was made of carefully-mortised, hand- polished boards and adorned with an excellent wood carving that depicted a running buck chased by wolves. Jeff and Dan breathed their delight. Except for the stove, the pots and pans that hung behind it, the lamps, and a few other articles that would be very difficult to fashion with hand tools, every bit of furniture had been made of whatever materials were available. But whoever made it had not been contented with something merely useful. Strict utility had received consideration, but beauty was in vast abundance. Jeff looked through a large window that faced the back and saw a neat garden, a little grove of fruit trees, a fat mule, a brown cow, and a cat sitting on a stone. It was exactly the big, fluffy, white cat that should have belonged in such a place. Not until he took a
- 48. second glance did he realize that the cat was not alive at all, but woven into a tapestry. He went nearer. Stretched on a walnut frame, the tapestry was so exquisitely woven that the cat's every hair not only showed but was in the right place. The cat was about to lick a front paw, and even after he knew it was a tapestry, so real was the illusion of life that Jeff extended a hand to see if the cat might not be soft and warm. He turned to Granny. Who did this? She was all gentleness. I did. That's my Kitty Cat, dead these four months. There was longing in her voice, and more than a hint of sadness, and Jeff knew that the cat had meant a great deal to her. He understood. Some people loved horses, some preferred dogs, and some set their affections on cats. But for Granny it could not be just any cat. Jeff asked, Do you do much of this sort of thing? Land, yes! A body ought to keep busy! Jeff said gently, I think you've kept busy a long while around here. Sixty-four years the seventh of May, she said pertly. Came as a sixteen-year-old bride. Enos, God rest his soul, has been gone these past three years. You two come on into the kitchen. She led them into the kitchen, seated them, opened a trap door in the floor, took cool milk from an earth-bound chamber, and lifted a tray of gingerbread from a cabinet. Eighty years old, her movements were almost as brisk and sure as a girl's. Jeff and Dan ate heartily; any food they prepared for themselves could not possibly compare with this. Granny seated herself companionably near. Ike say when he was gettin' out? she asked.
- 49. Well, no. He was there with Bucky— Jeff snapped his fingers. I forgot his last name. Bucky Edwards, she furnished. Land! He and Ike been stealin' chickens for a span of time. Jeff sensed something completely fine. She was old in years only. Until the day she died her mind would be young and strong. Ike's escapades probably did hurt her, but Ike was as much her son as the doctor, the lawyer and the others who had decided in favor of respectable careers. She would not deny him. Jeff said, Ike and Bucky didn't seem to have any definite plans. They have some, she assured him. They'll come here, and when they do, there'll be a heap of trouble— She stopped suddenly, as though she had said something unwise. When do you expect them? Jeff asked. Don't rightly know. Maybe soon. Maybe not so soon. For a moment Jeff was silent and Dan was still stuffing gingerbread into his mouth. Granny had spoken of trouble when Ike came, but apparently it was not trouble for herself, and if she wanted him to know more about it she would have told him. He wished he could offer her help, but he had an uncomfortable feeling that she knew how to help herself. He was trying to think of a way to steer the conversation away from Ike when Granny relieved him of the necessity for so doing. What you peddlin'? she asked brightly. Jeff fidgeted. The contents of his pack, for the most part, were designed for those who had little. Jeff tried to please people who yearned after a bit of gay ribbon, a new knife, anything they might need or desire but could not get for themselves. But he couldn't imagine what Granny lacked and countered her question with one of his own.
- 50. Where do you get your thread and yarn? She looked surprised. Spin it myself, to be sure. I have sheep. I grow flax, too. Jeff followed up because he was interested. Do you also make your own dyes? Land, yes! 'Twould be a sin to let the yarbs go to waste when they grow right at the door step! Do you use anything besides herbs? Bark, seeds, nut husks and shells, it's all here. Take a bit of this, a bit of that, a bit of another thing, seethe it, and there's a dye. I know you do your own weaving. Land, yes! Jeff grinned ruefully. For the first time since its founding, Tarrant Enterprises, Ltd., had reached a blind end. Something for Everyone, was one of its numerous slogans. But he did not have anything for Granny Wilson and he was honest about it. Granny, I don't believe I can offer you a thing. Oh, come now! You must have somethin'! But I haven't. Now, Jeff, you jest open that pack and give me a look for myself. I'll do that much. Jeff laid his pack on the table and opened every compartment. Granny reached for a skein of gray yarn. She tested it with her fingers, murmured, Poorly, poorly, and handed it back. Granny ignored the bright ribbons, had no time whatever for the knickknacks, lingered over a packet of needles, and her eyes were accusing when she gave them back.
- 51. Young man, you are a poor shakes of a peddler. I tried to tell you I hadn't anything you'd want. You should have somethin' to please a poor old woman. I know. If I had anything good enough for you—Oh, darn! A skein of yarn tumbled out of the pack and caught on a buckle. Jeff reached through the slit for one of the many-bladed knives, opened the scissors, and carefully snipped the tangled wool off. Granny clapped joyful hands. I knew it! I knew it! Give me that. Jeff handed her the knife. Granny's eyes shone. Just the thing! she cried ecstatically. Just what I need! My eyes ain't what they used to be. I missed two shots at runnin' bucks last fall and I'm forever mislayin' my necessaries. 'Twould be handy to have so many in one piece. Cash or swap? Jeff said recklessly, Let's call it a gift, Granny. But, she was honestly troubled, you can't give me aught that cost you dear. Yes I can. Not by my leave, she said firmly. It's only right that a body gets his worth. I'll swap even for a look at some of your other tapestries. My what? Your cloth pictures, like the cat. Land! I'll get some. She bounced from her chair, bustled into an adjoining room, and they heard her open a trunk. A moment later she was back with two
- 52. tapestries under her arm. She spread one, a yard long by about twenty inches wide, and Jeff gasped. It was The Last Supper, but instead of following conventional patterns, Granny had drawn inspiration from the life around her. Jesus and His disciples were seated at a wooden table that was innocent of any adornment or finery whatsoever, but the table was so finely done that a sliver thrusting out from it seemed both real and symbolic. There was an air of dignity that rose above mere human dignity, and the dyes had been applied with a touch so delicate that holy light seemed to emanate from the picture. Its message was one of hope. Judas was not to be abandoned. Do you like it? Granny asked. It— Jeff was at a loss for words. It's wonderful! Preacher Skiles thinks the Lord ain't right. Preacher Skiles assumes a great deal of responsibility. She laughed. 'Twas not the way he meant it. He thinks Jesus should be sittin' above the rest, with maybe angels flyin' at His shoulder. It's better this way. That's what I thought, Granny asserted. The Lord, He wasn't above the beggars, the sick and those who done wrong. Somehow I got to think of Him as comin' down to all of us. I, too. This one, Granny spread the other tapestry, I call The Fall of Satan. Jeff gasped again. The picture centered around the black silhouette of Satan, with a background done in delicate shades of red. There was about the figure utter misery, abandonment and despair. The gates of hell, which he had not yet entered, were merely suggested.
- 53. But they were suggested so artistically that one sensed the seething fires, the complete torment, that awaited. Dan looked and shuddered. Gee! Jeff breathed, Why hasn't anyone else seen these, Granny? Enos, she answered, didn't hold with hangin' them on the walls and I've tried to keep the house as Enos'd want it. But I knew Enos wouldn't mind Kitty Cat. He—he's company. Somebody should see them. Pooh! Who'd bother with an old woman's foolishness? I would. Then take them. Take them for the knife. I won't do it. She seemed crestfallen. I didn't think you would. Jeff said seriously, It isn't that. These are worth a great deal of money. They are? How much? Jeff hazarded a guess, Twenty-five dollars. Land! Each, Jeff finished. My land! Granny, do you trust me? Pooh! I didn't raise eight of my own 'thout knowin' aught of boys. Are these dear to you? I don't set much store by 'em. Enos never liked 'em.
- 54. Let me take them into Ackerton, Jeff urged. Let me see what I can do with them there. Go ahead if you've a mind to. Land! Meal time and I haven't started a thing for you boys to eat!
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