GROUP TECHNOLOGY Chapter 10

1. GROUP TECHNOLOGY Chapter 10

2. GROUP TECHNOLOGY GROUP TECHNOLOGY IS A MANUFACTURING TECHNIQUE AND PHILOSOPHY TO INCREASE PRODUCTION EFFICIENCY BY EXPLOITING THE “UNDERLYING SAMENESS” OF COMPONENT SHAPE, DIMENSIONS, PROCESS ROUTE, ETC.

3. Group Technology is the realization that many problems are similar, and that by grouping similar problems, a single solution can be found to a set of problems thus saving time and effort. (Solaja 73) • First book formalize the concept: Mitrofanov,S.P. 1958, "The Scientific Principles of Group Technology"

4. Why Group Technology? • Average lot size decreasing • Part variety increasing • Increased variety of materials • With diverse properties • Requirements for closer • tolerances

5. HIGH FLEXIBILITY TRANSFER LINE PRODUCTION CAPACITY SPECIAL SYSTEM FLEXIBLE MANUFACTURING SYSTEM VOLUME MANUFACTURING Cells STD. AND GEN. MACHINERY LOW HIGH VARIETY

6. Everyday Examples 1. Fast food chains 2. Doctors, dentists and also manufacturing A FAMILY OF PARTS

7. Production Family

8. Lack Of Common Database For • Mfg., Design... • Don’t “redesign the wheel” • Automated process planning • Database to drive the • automated factory

9. Benefits Of Group Technology Reductions in Throughput time Set-up time Overdue orders Production floor space Raw material stocks In-process inventory Capital expenditures Tooling costs Engineering time and costs New parts design New shop drawings Total number of drawings Cont’d

10. Other Benefits Of Group Technology Easier to justify automation Standardization in design Data retrieval Easier, more standardized process plans Increases in quality

11. Gt affects most every operating and staff function. It is more than merely a technique, but a total Manufacturing philosophy. DESIGN ENGINEERING DATA PROCESSING SALES MAINTENANCE INVENTORY TOOL ENGINEERING PLANNING ESTIMATING PURCHASING INDUSTRIAL RELATIONS ASSEMBLY QUALITY CONTROL MANAGEMENT MFG. ENGINEERING R & D COST ACCOUNTING SHIPPING & RECEIVING GT

12. Three Techniques To Form Part Families 1. Tacit judgment or visual inspection • May use photos or part • prints • Utilizes subjective • judgment 2. Production Flow Analysis • Uses information contained • on the route sheet • (therefore only mfg. Info) • Parts grouped by required • processing Cont’d

13. 3. Classification And Coding • Codes geometry/design and mfg. • Info about a component • Codes are alphanumeric strings • Easier to use for other analyses

14. Types Of Classification And Coding Systems GT coding can benefit many facets of the Firm and fall into one of 3 categories: 1. Systems based on part design Attributes 2. Systems based on part mfg. Attributes 3. Systems based on design and mfg. Attributes

15. Examples: Part Design Attributes Basic external shape Basic internal shape Material Part Mfg. Attributes Major processes Minor operations Fixtures needed Length/diameter ratio Surface finish Tolerances-----machine tool Operation sequence Major dimension Tooling Batch size

16. GT Code--a Sequence Of Numerical Digits Three major structures: 1. Monocode (or hierarchical structure) A code in which each digit amplifies the information given in the previous digit • Difficult to construct • Provides a deep analysis • Usually for permanent information cont’d

17. 2. Polycode (Or Chain-type Structure) Each digit is independent of all others, presents information not dependent On previous ones • Easier to accommodate • Change 3. Mixed Code Has some digits forming monocodes, but strings them together in the general Arrangement of a polycode

18. MAPPING FROM POPULATION SPACE TO CODE SPACE POPULATION SPACE H P CODE SPACE C

19. 3231 3233 3221 3223 Hierarchical Structure 32XX Hydraulic Electrical 321X 323X Mechanical Power Receiving Transmission 322X 3232 UNC thread No thread UNF thread 3222

20. Hybrid Structure Polycode Polycode Monocode

21. Improvements in Engineering Design Materials Management & Purchasing Benefits Production Control Benefits Manufacturing Engineering Benefits Tooling & Setup Benefits Management Benefits Overall Cost Reduction & Increased Productivity 0 6 12 18 24 36 Time (months) Reduction Of Mfg. Costs By Various Steps Of Group Technology Applications (Adapted From Ham442) Not All Cost Savings Are Immediate...

22. Proliferation Of Parts Selection of optical instrument parts in one company, Illustrating the similarity between certain components • Note: some of the above are almost the same

23. Design concept can be coded. Code is a rough model of the conceptual design. Conceptual design Coding (rough model) Retrieval existing designs Existing designs Design modification New Design Design archive Retrieve designs of similar shape or function and use them as the examples.

24. Technique: 1. Determine part and machine requirements 2. Numerically code each part Geometry (& size) Material Other specifications (tolerance, Surface finish) 3. Form a family of similar parts which use (Largely) the same set of machine tools 4. Lay out of each cell (a group of machine Tools) to make a family of parts 5. Design group tooling

25. Example: Thirteen parts with similar manufacturing Process requirements but different Design attributes

26. Functional Layouts Are Inefficient Drilling Milling Lathe D D L M L M D D L L M M Grinding G L L M G M Assembly G G L L A A G G A Receiving and Shipping A PROCESS-TYPE LAYOUT

27. L G G L M Group Technology Layout G D M L A A Receiving D M L Shipping

28. Cellular Layout Department #2 Department #1 D D M I D I L Department #3 M M L D L I M

29. Supplim- entary code Digit 6 7 8 9 External shape element Internal shape element Machining of plane surfaces Other holes and teeth Other holes teeth and forming Machining of plane surfaces Form Code Rotational machining Main shape Dimensions Material Original shape of raw materials Accuracy Main shape Main bore & rotational machining Other holes teeth and forming Machining of plane surfaces Main shape Main shape 1st Digit part class 5th Digit additional holes teeth & forming 3rd Digit rotational machining 4th Digit plane surface matching 2nd Digit main shape Positions with a digit 0 1 2 Rotational 3 4 5 Special 6 7 Non-rotational 8 Opitz coding and classification system. (Reprinted with permission from H. Opitz, A Classification System to Describe Workpieces, Pergamon Press.) 9 Special

30. XXX Process planning system Process APT Program APT Processor & post-processor Engineering drawing Typical Process Planning System Process planner Code or other form of input • Industrial engineer • Time standard • Operation • instruction • Layout • Production planner • Scheduling • MPP Part programmer

31. Process Planning “Process planning” is that function within a manufacturing Facility that establishes which machining processes and Parameters are to be used (as well as those machines capable Of performing these processes) to convert (machine) a piece Part from its initial form to a final form predetermined (usually by a design engineer) from an engineering drawing. (I.E. The preparation of the detailed work instructions to Produce a part) Process planning bridges design and manufacturing Bridge Design Manufacturing

32. Variant Process Planning Uses the similarity among components to retrieve existing process plans (which can be modified) Overview: Two Stages For VP Systems 1. Preparatory stage • Existing parts coded & • classified (i.E. Gt is a • prerequisite) • Part families organized • Standard plans developed • Databases created (Note: this stage is labor intensive) Cont’d

33. 1. Preparatory Stage Of Variant Process Planning Part Drawing Coding Family One Standard Plan File Family Formation (Indexed by Family Matrix) Process Plan

34. 2. Production Stage Of Variant Process Planning Family Search Coding Standard Plan File Process Plan Standard Plan Retrieval Editing