GROUP TECHNOLOGY Chapter 10

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.

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"

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

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

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

Production Family

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

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

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

Gt affects most every 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

Three Techniques To Form 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

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

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

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

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

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

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

UNF thread Transmission Hierarchical Structure Hydraulic Electrical Mechanical 32XX 321X 322X No thread UNC thread X Power Receiving

Monocode Polycode Hybrid Structure

Reduction Of Mfg. Costs By Various Steps Of Group Technology Applications (Adapted From Ham 442 ) 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 Time (months)

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

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.

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

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

Functional Layouts Are Inefficient PROCESS-TYPE LAYOUT Lathe Milling Drilling Grinding Assembly Receiving and Shipping L LL L L L L L M M M MM M AA A A D DD D G G G G G G

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

Department #2 Department #3 Department #1 D D MI D M L L I D M L M I Cellular Layout

1st Digit part class Positions with a 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 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 Supplim- entary code Digit Dimensions Material Original shape of raw materials Accuracy

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

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

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

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

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