DFA, Coding, CAPP engineering industrial .ppt

Computer Integrated
Manufacturing
Design For Automation,
Coding and Classification,
Computer Aided Process Planning

Design For Automation
• While many factory processes are not yet automated, new products
in the era of Industry 4.0 must—at the very least—be prepared for
automation.
• Automation technologies require new and complex design
considerations that engineers must take into account. We call this set
of considerations Design for Automation (DFA).

Rules for Designing for Automation
• Here are five simple rules to follow as you prepare your products for the
future:
1. Think like a robot.
• Imagine a robot in an assembly line, with its robotic arms. Compared to human
arms, robotic arms are quite limited in their motion range and capabilities.
2. One direction is best (No, I’m not talking about the boyband).
3. Consider Off the Shelf
• All manufacturers rely on off-the-shelf parts (OTS) to complete their products,
whether it’s fasteners, dowel pins, electrical connectors or others. To ensure your
product is DFA-ready, it is always a good idea to ask yourself if those
miscellaneous parts are approachable for automation.
4. Prepare for the camera.
5. Don’t forget about the packaging

CODING AND CLASSIFICATION
• Coding is a process of establishing symbols to be used for meaningful
communication.
• Classification is a separation process in which items are separated into
groups based on the existence or absence of characteristic attributes.
• Coding can be used for classification purposes, and
• Classification requirements must be considered during the
construction of a coding scheme.
• Therefore, coding and classification are closely related.

CODING
• Before a coding scheme can be constructed, a survey of all component
features must be completed and then code values can be assigned to
the features.
• The selection of relevant features depends on the application of the
coding scheme.
• For example, tolerance is not important for design retrieval; therefore, it is not
a feature in a design oriented coding system.
• However, in a manufacturing-oriented coding system, tolerance is indeed an
important feature.

CODING
• Because the code structure affects its length, the accessibility
and the expandability of a code ( and the related database) is
of importance. There are three different types of code
structure in GT coding systems:
(1) hierarchical, also is called a monocode
(2) chain (matrix), also is called a polycode, and
(3) hybrid.

Hierarchical Structure Type (Monocode)
• In a monocode, each code number is qualified by the preceding
characters.
• For the example shown, the fourth digit indicates threaded or not
threaded for a 322X family.
• One advantage of a hierarchical
structure is that it can represent a large
amount of information with very few
code positions.
• A drawback is the potential
complexity of the coding system.
• Hierarchical codes are difficult to
develop because of all the branches in
the hierarchy that must be defined.

Chain Structure Type (Polycode)
• Chain structure. Every digit in the code position represents a distinct
bit of information, regardless of the previous digit.
• A 2 in the third position always means a cross hole no matter what numbers are
given to positions 1 and 2.
• Chain codes are compact and are much easier to construct and use.
• The major drawback is that they cannot be as detailed as hierarchical structures
with the same number of coding digits.

Hybrid Structure Type
• The hybrid structure, is a mixture of the hierarchical and chain
structures.
• Most existing coding systems use a hybrid structure to obtain the advantages of
both structures.
• A good example is the widely used Opitz (1970) code.
• There are more than 100 GT coding systems used in industry today.

Hybrid Structure Type: Opitz code

Hybrid Structure Type: Opitz code
Example: A rotational component is coded using the Opitz system. By going
through each code position, the resulting code becomes 11102. This code represents
this component and all others with similar shape and diameter.

Operations
and
Machines
for
the
Machining
of
Surfaces

MANUAL PROCESS PLANNING
• In a conventional production system, a process plan is created by a process
planner who examines a new part ( engineering drawing) and then determines the
appropriate procedures to produce it.
• In order to prepare a process plan, a process planner has to have the following
knowledge:
• Ability to interpret an engineering drawing
• Familiarity with manufacturing processes and practice
• Familiarity with tooling and fixtures
• Know what resources are available in the shop
• Know how to use reference books, such as machinability data handbooks
• Ability to do computations on machining time and cost
• Familiarity with the raw materials
• Know the relative costs of processes, toolings, and raw materials

MANUAL PROCESS PLANNING: Example
The following features are identified:
• Sl: end surface/face
• S2: ·2.752-in. cylindrical surface
• S3: flat surface/face
• S4: large diameter, 5.25-in. diameter with
chamfer of 0.25 in. radius
• S5: threaded cylinder with 0.25 in. X 0.25 in
neck recess
• S6: flat surface/face
• S7: 1.627-in.-diameter bore
• S8: four counterbored holes

MANUAL PROCESS PLANNING: Example
The following is the sequence of operations:
Setup 2:
• Chuck the workpiece on S4.
• Turn S5 to 2.75-in . diameter.
• Thread S5.
• Undercut the neck.
• Face S6.
• Remove the part and move it to a drill press
Setup 3 :
• Locate the workpiece using S2 and S7 .
• Mark and center drill four holes, S8 .
• Counterbore four holes , S8.
Setup 1 :
• Chuck the workpiece .
• Turn S4 to a 5.25-in. diameter .
• Turn S2 to a 2.750-in. diameter .
• Face S1 and then S3.
• Core drill and drill S7.

Automating Process Planning
• Process planning is a task that requires a significant amount of both time and
experience.
• According to an Air Force study, a typical process planner is a person
approximately 50 years of age with significant experience in a machine shop.
• Although U.S. industry requires about 200,000 to 300,000 process planners, only
150,000 to 200,000 are currently available.
• Automating process planning is an obvious alternative to alleviate this problem.

COMPUTER-AIDED PROCESS PLANNING
• The input to the system will most probably be a three-
dimensional model from a CAD database.
• The model contains not only the shape and
dimensioning information, but also the tolerances and
special features.
• The process plan can be routed directly to the
production-planning system and production-control
system.
• Time estimates and resource requirements can be sent
to the production-planning system for scheduling.
• The part program, cutter-location (CL) file, and
material-handling control program can also be sent to
the control system.

VARIANT PROCESS PLANNING:
• A variant process-planning system uses the similarity among components to
retrieve existing process plans.
• A process plan that can be used by a family of components is called a standard
plan.
• A standard plan is stored permanently in the database with a family number as its
key.
• There is no limitation to the detail that a standard plan can contain.
• However, it must contain at least a sequence of fabrication steps or operations.
• When a standard plan is retrieved, a certain degree of modification is usually
necessary in order to use the plan on a new component.

In general, variant process-planning systems have two operational stages: a
preparatory stage and a production stage.
1. The Preparatory Stage
2. The Production Stage
VP is used in a machine shop that produces a variety of small components. These
components range from simple shafts to delicate hydraulic-pump parts. We discuss
the construction of VP in the following sequence:
1. Family Formation
2. Database Structure
3. Search Algorithm
4. Plan Editing
5. Process-parameter Selection

Generative process planning is a second type of computer-aided process planning.
• It can be concisely defined as a system that synthesizes process information in
order to create a process plan for a new component automatically.
• In a generative planning system, process plans are created from information
available in a manufacturing database without human intervention.
• Upon receiving the design model, the system can generate the required
operations and operations sequence for the component.
Successful implementation of this approach requires the following key developments:
1. Process-planning knowledge must be identified and captured.
2. The part to be produced must be clearly and precisely defined in a computer-readable
format (e.g., three-dimensional model or GT code).
3. The captured process-planning knowledge and the part description data must be
incorporated into a unified manufacturing database.

DFA, Coding, CAPP engineering industrial .ppt

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