GROUP TECHNOLOGY AND COMPUTER
AIDED PROCESS PLANNING
1. Group technology (GT)
Group technology (GT) is a
manufacturing philosophy to increase production efficiency by grouping a
variety of parts having similarities of shape, dimension, and/or process route.
2. Part family
A part family is a collection of
parts which are similar either because of geometric shape and size or because
similar processing steps are required in their manufacture. Design
attributes:
·
Part configuration (round or prismatic)
·
Dimensional envelope (length to diameter ratio)
·
Surface integrity (surface roughness, dimensional
tolerances)
·
Material type & Raw material state (casting,
forging, bar stock, etc.)
Part manufacturing features:
Operations and operation
sequences (turning, milling, etc.)
·
Batch sizes
·
Machine tools
·
Cutting tools
·
Work holding devices
·
Processing times
3. General
methods used for part families.
4. Visual
inspection,
5. Parts
classification and coding system, and
6. Production
flow analysis.
4. Production
Flow analysis
Production Flow analysis (PFA) is
a method for identifying part families and associated machine groupings that
uses the information contained on production route sheets rather on part
drawings.
5. Code
structures used in GT application
· Attribute
codes (or polycodes or chain type structure).
· Hierarchical
codes (or monocodes or tree structure).
· Decision-tree
codes (or hybrid codes or mixed codes).
6. Coding
systems.
1.
Opitz classification system, 2.
MICLASS system,
3.
DCLASS system, 4. CODE
system,
5.
KK-3 system,and 6.
CUTPLAN system.
7. Benefits of Group Technology
Group technology is a management strategy to help
eliminate waste caused by duplication of effort.
It
affects all areas of a company, including:
· Engineering
· Equipment
specification
· Facilities
planning
· Process
planning
· Production
control
· Quality
control
· Tool
design
· Purchasing
· Service
7. Cellular
manufacturing
Cellular manufacturing (CM) is an
application of group technology in which dissimilar machines have been
aggregated into cells, each of which is dedicated to the production of a part
family.
8. Design
considerations guiding the cell-formation.
·
Parts/products to be fully completed in the cell.
·
Higher operator utilization.
·
Fewer operations than equipment.
·
Balanced equipment utilization in the cell.
9. Process
planning
Process Planning is the
systematic determination of the methods by which a product is to be
manufactured, economically and competitively.
10.
Computer/Aided Process Planning
§ CAPP
refers to computer/aided process planning.
§ CAPP is
used to overcome the drawbacks of manual process planning.
§ With the
use of computers on the process planning one can reduce the routine clerical
work of manufacturing engineers.
§ Also it
provides the opportunity to generate rational, consistent and optimal
plans.
11.
Process planning techniques used in the
modern manufacturing technologies
§ Manual
approach
§ Computer
aided process planning techniques
§ Retrieval
type CAPP system (Variant type CAPP system)
§ Generative
type CAPP system
12.
CAPP;
Computer aided process planning
system offers the potential for reducing the routine clerical work of
manufacturing engineers. It provides the opportunity to generate routings which
are rational, consistent and perhaps even optimal.
13. Retrieval type CAPP (Variant type) systems
For each part family a standard
process plan is established and stored in computer files and then it is
retrieved for new work parts which belong to that family. Because of the
alterations that are made in the retrieved process plan, the CAPP system is known
as variant system.
14. Generative CAPP system
Generative process planning
involves the use of computer to create an individual process plan automatically
without human assistance. The computer would employ a set of algorithms to
progress through the various technical and logical decisions toward a final
plan.
15.
Role of process planning
1. Interpretation
of product design data
2. Selection
of machining processes.
3. Selection
of machine tools.
4. Determination
of fixtures and datum surfaces.
5. Sequencing
the operations.
6. Selection
of inspection devices.
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