1. UNIT-III Group Technology and Computer Aided Process Planning

2. Group Technology
GT is a manufacturing philosophy to increase production effectively by grouping a variety of parts having similarities of shape, dimension and/or process route

3. Part families
Collection of parts which are similar either because of geometric shape and size (or) because similar processing steps are required in the manufacturing.
Design Part Family
Grouped the parts similar in their design (shape & geometry) characteristics
Manufacturing Part Family
Grouped the Parts similar in their manufacturing characteristics ( Mfg. Process)

4. Methods for part family formation
Visual inspection
Parts classification and coding system
Production flow analysis

5. Visual Inspection
It involves looking of parts, photos of parts (or) drawings of parts and arranging them into similar groups

6. Parts Classification and Coding System
Coding is a systematic process of establishing an alphanumeric value for parts based on selected part families
Most difficult , most time- consuming , most sophisticated and widely used methods
It will vary from one company to another company

7. Coding System Structure
Hierarchical Code
Attribute Code
Decision tree codes

8. Hierarchical Code (Monocode)
The interpretation of each successive symbol depends on the value of the proceeding symbols.

9. Hierarchical Code

10. Example-Spur gear

11. Merits and Demerits
It Provides large amount of information relatively small no. of digits
Defining the meanings for each digit in a hierarchical system is difficult

12. Attribute Code (Polycode)
The interpretation of each symbol in the sequence does not depend on the value of preceding symbols
Each digit in this code represents information in its own right and does not directly qualify the information provided by the other digits

13. Example-Spur Gear

14. Merits and Demerits Polycodes are compact and easy to use
Its lacks in detail as compared to monocode

15. Decision tree codes (Hybrid Code)
Hybrid code Captures the best features of the hierarchical and polycode structures
It combines both design and manufacturing attributes

16. Decision tree codes (Hybrid Code)

17. Reasons for using a coding scheme
Design retrieval
Automated process planning
Machine cell design

18. Selection of a Coding System
Objective-of the classification system
Robustness- Capability of handling all parts
Expandability- Ability to cope up with future demands
Automation- for computer use
Efficiency- the code efficiency, the no. of digits required to code a typical part, should be evaluated.
Cost- including initial, modifying, interfacing and operational costs
Simplicity – ease of use training

19. Coding Systems Opitz Classification systems MICLASS Systems
DCLASS System
KK-3 System
CODE System
CUTPLAN System
RNC System
Part Analog System
Brisch System
COFORM

20. Opitz Classification systems

21. Production flow analysis (PFA)
Identifying part families and associated machine groupings that uses the information contained on production route sheets rather on part drawings

22. Steps involved in Production flow analysis
Data collection- (part no. o/p sequence)
Sorting of process routings- (Group technology- Arranging of Process Types)
Preparation of PFA chart-Tabulation of a Process of a machine.
Cluster Analysis

23. Steps involved in Production flow analysis

24. Facility Design using Group Technology
Line (or product) Layout
Functional (or Process ) Layout, and
Group (or combination ) layout

25. Line (or product) Layout
Machines are arranged in the sequence as required by the product

26. Functional (or process) Layout
Keeping similar machines/operations at one location

27. Group (or Combination) Layout
Combination of Product layout and process layout

28. Cellular Manufacturing (CM)
Cellular Manufacturing, production work stations and equipment are arranged in a sequence that supports a smooth flow of materials and components through the production process with minimal transport or delay.

29. Process Planning
The product design for the each product developed in design department.
To convert the product design into product , a manufacturing plan is required.
The activity of developing such a plan is called Process Planning
“An Act of preparing a detailed processing documentation for the manufacture of a piece part or assembly”

30. Document Process Planning
Clear in detail about the particular product in form of route and operation sheet

31. Approaches of Process Planning
1.Manual Process Planning 2.Computer Aided Process Planning i) Retrieval CAPP System ii) Generative CAPP System

32. Manual Process Planning
Merits:
Its very much suited for small scale industries
It requires low investment costs
Demerits:
Its time consuming
Required skill process planner
It increases paper work

33. Computer Aided Process Planning (CAPP)
CAPP- Use of computers in the process planning, one can reduce the routine clerical work of manufacturing engineers
Benefits:
Process rationalization and standardization
Productivity improvement
Product cost reduction
Elimination of human error
Reduction in time
Reduced clerical effort and paper work
Faster respond to engineering changes

34. Computer Aided Process Planning (CAPP)

35. Variant (or) Retrieval CAPP Systems
A process plan for a new part is created by identifying and retrieving an existing plan for a similar part, followed by the retrieving an existing plan for a similar part, followed by the necessary modifications to necessary modifications to adapt it to the new part.

36. Variant (or) Retrieval CAPP Systems
Variant approach is commonly implemented with GT coding system. Here, the parts are segmented into groups based on similarity and each group has a master plan.

37. Advantages
Once a standard plan has been written, a variety of components can be planned.
Programming and installation are comparatively simple.
It is easy to learn and easy to use.

38. Disadvantages
The components to be planned are limited to previously planned similar components.
Experienced process planners are still required to modify the standard plan for the specific component.
Variant planning cannot be used in an entirely automated manufacturing system, without additional process planning.

39. Generative CAPP System
In a generative approach, a process plan for each component is created from scratch without human intervention. These systems are designed to automatically synthesize process information to develop a process plan for a part. (Computer Automatically generates a unique operation/route sheet whenever the part is ordered)

40. Generative CAPP System
Generative CAPP systems contain the logic to use manufacturing data bases, knowledge bases and suitable part description schemes to generate a process plan for a particular part.

41. Advantages and Disadvantages
Consistent process plans can be generated rapidly.
New components can be planned as easily as existing components.
It has potential for integrating with an automated manufacturing facility to provide detailed control information.
The generative approach is complex and very difficult to develop