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Unit 5 Group Technology in Computer Aided Design
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- 2. GROUP TECHNOLOGY GROUP TECHNOLOGYIS A MANUFACTURING TECHNIQUE AND PHILOSOPHY TO INCREASE PRODUCTION EFFICIENCY BY EXPLOITING THE “UNDERLYING SAMENESS” OF COMPONENT SHAPE, DIMENSIONS, PROCESS ROUTE, ETC.
- 3. • Group Technologyis 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. FLEXIBILITY PRODUCTION CAPACITY TRANSFER LINE SPECIAL SYSTEM FLEXIBLE MANUFACTURING SYSTEM MANUFACTURING Cells STD. ANDGEN. MACHINERY VOLUME HIGH VARIETY LOW HIGH
- 6. EVERYDAY EXAMPLES 1. FASTFOOD CHAINS 2. DOCTORS, DENTISTS AND ALSO MANUFACTURING A FAMILY OF PARTS
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- 8. • LACK OFCOMMON DATABASE FOR MFG., DESIGN... • DON’T “REDESIGN THE WHEEL” • AUTOMATED PROCESS PLANNING • DATABASE TO DRIVE THE AUTOMATED FACTORY
- 9. BENEFITS OF GROUPTECHNOLOGY 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 OFGROUP TECHNOLOGY EASIER TO JUSTIFY AUTOMATION STANDARDIZATION IN DESIGN DATA RETRIEVAL EASIER, MORE STANDARDIZED PROCESS PLANS INCREASES IN QUALITY
- 11. GT AFFECTS MOSTEVERY OPERATING AND STAFF FUNCTION. IT IS MORE THAN MERELY A TECHNIQUE, BUT A TOTAL MANUFACTURING PHILOSOPHY. GT DESIGN ENGINEERING DATA PROCESSING MAINTENANCE TOOL ENGINEERING ESTIMATING INDUSTRIAL RELATIONS QUALITY CONTROL R & D COST ACCOUNTING SALES INVENTORY PLANNING PURCHASING ASSEMBLY MANAGEMENT MFG. ENGINEERING SHIPPING & RECEIVING
- 12. THREE TECHNIQUES TOFORM PART FAMILIES 1. TACIT JUDGMENT OR VISUAL INSPECTION 2. PRODUCTION FLOW ANALYSIS • MAY USE PHOTOS OR PART PRINTS • UTILIZES SUBJECTIVE JUDGMENT • USES INFORMATION CONTAINED ON THE ROUTE SHEET (THEREFORE ONLY MFG. INFO) • PARTS GROUPED BY REQUIRED PROCESSING Cont’d
- 13. 3. CLASSIFICATION ANDCODING • CODES GEOMETRY/DESIGN AND MFG. INFO ABOUT A COMPONENT • CODES ARE ALPHANUMERIC STRINGS • EASIER TO USE FOR OTHER ANALYSES
- 14. TYPES OF CLASSIFICATIONAND 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 BASICEXTERNAL 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 SEQUENCEOF 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 (ORCHAIN-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
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- 21. REDUCTION OF MFG.COSTS BY VARIOUS STEPS OF GROUP TECHNOLOGY APPLICATIONS (ADAPTED FROM HAM442 ) Improvements in Engineering Design Materials Management & Purchasing Benefits Production Control Benefits Manufacturing Engineering Benefits Tooling & Setup Benefits Management Benefits Overall Cost Reduction & Increased Productivity NOT ALL COST SAVINGS ARE IMMEDIATE... 0 6 12 18 24 36 Time (months)
- 22. SELECTION OF OPTICALINSTRUMENT PARTS IN ONE COMPANY, ILLUSTRATING THE SIMILARITY BETWEEN CERTAIN COMPONENTS • PROLIFERATION OF PARTS • NOTE: SOME OF THE ABOVE ARE ALMOST THE SAME
- 23. GT FOR DESIGNAPPLICATION 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. Design concept can be coded. Code is a rough model of the conceptual design.
- 24. TECHNIQUE: 1. DETERMINE PARTAND 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 WITHSIMILAR MANUFACTURING PROCESS REQUIREMENTS BUT DIFFERENT DESIGN ATTRIBUTES
- 26. FUNCTIONAL LAYOUTS AREINEFFICIENT PROCESS-TYPE LAYOUT Lathe Milling Drilling Grinding Assembly Receiving and Shipping L L L L L L L L M M M M M M A A A A D D D D G G G G G G
- 27. GROUP TECHNOLOGY LAYOUT Shipping LL M D L M D G L M G G A A Receiving
- 28. Department #2 Department #3 Department#1 D D M I D M L L I D M L M I CELLULAR LAYOUT
- 29. 1st Digit part class Positions witha digit 2nd Digit main shape 3rd Digit rotational machining 4th Digit plane surface matching 5th Digit additional holes teeth & forming FORM CODE Opitz coding and classification system. (Reprinted with permission from H. Opitz, A Classification System to Describe Workpieces, Pergamon Press.) Special Non-rotational Special Rotational 9 8 7 6 5 4 3 2 1 0 Internal shape element Rotational machining Main bore & rotational machining Other holes and teeth Other holes teeth and forming Other holes teeth and forming Machining of plane surfaces Machining of plane surfaces Machining of plane surfaces External shape element Main shape Main shape Main shape Main shape Supplim- entary code Digit 6 7 8 9 Dimensions Material Original shape of raw materials Accuracy
- 30. Process planning system APT Processor &post-processor APT Program Process XXX TYPICAL PROCESS PLANNING SYSTEM Part programme r Production planner • Scheduling • MPP Industrial engineer • Time standard • Operation instruction • Layout Engineering drawing Process planner Code or other form of input
- 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) Bridge Design Manufacturing Process planning bridges design and manufacturing
- 32. VARIANT PROCESS PLANNING USESTHE 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. Part Drawing Coding Family Formation ProcessPlan Family One Standard Plan File (Indexed by Family Matrix) 1. PREPARATORY STAGE OF VARIANT PROCESS PLANNING
- 34. 2. PRODUCTON STAGEOF VARIANT PROCESS PLANNING Coding Family Search Standard Plan File Editing Standard Plan Retrieval Process Plan