IE 590 INTEGRATED MANUFACTURING GROUP TECHNOLOGY

1. IE 590 INTEGRATED MANUFACTURINGGROUP TECHNOLOGY J Cecil IE 590 NMSU

2. CAM-I Automated Process Planning System • One of the most well-known systems is the CAM-I Automated Process Planning (CAPP) system • DO NOT CONFUSE THE CONCEPTUAL TERM ‘CAPP’ (COMPUTER AIDED PROCESS PLANNING) WITH THE system‘CAPP’, WHICH IS FOR THE PROCESS PLANNING SYSTEM BUILT BY CAM-I • CAM-I stands for Computer Aided Manufacturing - International, which is a non profit industrial research organization J Cecil IE 590 NMSU

3. CAM-I Automated Process Planning System • In CAPP, previously prepared process plans are • stored in a database • When a new component needs to be planned, • a process plan for a similar component is retrieved • AND • subsequently modified by a human process • planner to satisfy specific requirements J Cecil IE 590 NMSU

4. VARIANT PROCESS PLANNING SYSTEMS (VPPS) • Variant process planning • uses similarity among parts or components to retrieve existing process plans • Standard Plan (SP): • A process plan that can be used by a family of parts • SP is usually stored permanently in the DB • Each SP has a FAMILY NUMBER as its KEY • No Limitation on the level of detail in an SP • AT A MINIMUM, AT LEAST A SEQUENCE OF OPERATIONS J Cecil IE 590 NMSU

5. VARIANT PROCESS PLANNING SYSTEMS (VPPS) • When an SP is retrieved, a certain min degree of modification is usually required to use the plan to manufacture a part • The retrieval method and the logic used in Variant Systems depend on the grouping of parts into families • Common manufacturing methods can be then identified for each family • Such common manuf methods can be rep by SPs J Cecil IE 590 NMSU

6. VPPS ......contd • Mechanism of standard plan retrieval is based on part families • A family can be rep by a family matrix, which includes all possible members • VPPS HAVE 2 OPERATIONAL STAGES: • PREPARATORY STAGE • PRODUCTION STAGE J Cecil IE 590 NMSU

7. VPPS ......contd • PREPARATORY STAGE: • Preparatory work is reqd when a company first starts implementing a VPPS • During this stage: • existing parts are coded • classified • then grouped into families • FIRST STEP IS TO CHOOSE AN APPROPRIATE CODING SYSTEM J Cecil IE 590 NMSU

8. PART CODING SYSTEMS AND ISSUES • CODING SYSTEM must cover the entire spectrum of parts produced in your shop • it must be UNAMBIGUOS and easy to understand • Special features on the parts MUST BE CLEARLY IDENTIFIED BY THE CODING SYSTEM • An Existing Coding system can be adopted and then modifications can be made for the specific manufacturing shop or facility J Cecil IE 590 NMSU

9. PART CODING SYSTEMS AND ISSUES • CODING REQUIRES DETAILED STUDY OF INVENTORY OF DRAWINGS / MODELS AND PROCESS PLANS • PERSONNEL INVOLVED IN CODING MUST BE TRAINED • they must have a precise understanding of the coding system • test: they must generate identical code for the same part, when they work independently • Note: inconsistent coding will result in redundant and erroneous data in the DATABASE DB J Cecil IE 590 NMSU

10. PART FAMILIES • After coding is completed, PART FAMILIES can be formed • Our interest is in grouping parts which may require similar manufacturing processes or operations • NOT NECESSARILY SIMILAR IN SHAPE J Cecil IE 590 NMSU

11. PART FAMILIES • Such a Set of similar parts can be called a PRODUCTION FAMILY • Since SIMILAR PROCESSES are needed for ALL FAMILY MEMBERS, A MACHINE CELL can be built or used to manufacture this family of parts • This makes production planning and control far easier. • Such a cell oriented layout is called a Group Technology layout or CELL LAYOUT. J Cecil IE 590 NMSU

12. GROUP TECHNOLOGY Please refer to chapter 13 of CAM book J Cecil IE 590 NMSU

13. GROUP TECHNOLOGY (GT) • In 1958, Mitrofanov (Russian engineer) formalized this concept in his book, The Scientific Principles of Group Technology • GT can be defined as: • “ 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” • This definition is broad; however, usually engineers relate GT only to manufacturing or production applications J Cecil IE 590 NMSU

14. PART FAMILIES • Design families: In part design, many parts may have similar shape (FIGURE 12.1) • similar parts can be grouped into design families • new design can be created by modifying existing part design from the same family • using this concept, composite parts can be developed • These parts embody all the design features of a design family • See FIGURE 12.1 J Cecil IE 590 NMSU

15. GROUP TECHNOLOGY (GT) • Production families : • are families formed because they require similar mfg operations to be produced • SEE FIGURE 12.3 J Cecil IE 590 NMSU

16. Coding and Classification • Three types: Hierarchical, chain and hybrid codes • Hybrid is widely used • Eg: Opitz code • Other examples are Vuoso-Praha and KK-3 (Japan) coding systems J Cecil IE 590 NMSU

17. HIERARCHICAL OR MONOCODE In a monocode, each code number is qualified by the preceding characters • SEE FIGURE 12.4 • The fourth digit indicates threaded or not threaded for family 322X • Advantage: large amount of info with few code positions • Disadvantage: potential complexity of coding system • all branches in hierarchy must be defined • hence, difficult to develop J Cecil IE 590 NMSU

18. Chain or PolyCode • Every digit in the code position rep. a distinct bit of info, regardless of previous digit • In Table 12.1, a chain coding scheme is given • A ‘1’ in the 3rd digit position always means an axial hole (no matter what numbers are assigned to digits 1 and 2) • Advantage: Compact and easy to construct / use • Disadvantage: They cannot be as detailed as hierarchical structures with same number of coding digits J Cecil IE 590 NMSU

19. Hybrid Code • mixture of chain and hierarchical code structures eg. Opitz code • Will discuss Opitz code in next section • Advantages of both can be obtained J Cecil IE 590 NMSU

20. FURTHER READINGS • Read the Vuoso Praha system (short code), KK-3 system (long code) • OPITZ CODE is most widely used and will be discussed • Also review MICLASS and DCLASS Systems J Cecil IE 590 NMSU

21. THE OPITZ CODE • BEST KNOWN AND MOST WIDELY USED • has 2 sections • geometric code • supplementary code • Geometric code • rep. Parts of following variety • Rotational, flat, long, cubic • Dimension ratio used to classify geometry • l/d ratio (for rotational) • l/width or l/height ratios (for non rotational / prismatic) J Cecil IE 590 NMSU

22. GEOMETRIC CODE • 5 Digits • Digits: • 1 - component class • 2 - basic shape • 3 - rotational surface machining • 4 - plane surface machining • 5 - auxiliary holes, gear teeth and forming • see table 12.4 (pages 483 and 484) J Cecil IE 590 NMSU

23. SUPPLEMENTAL CODE • 4 Digits APPENDED TO GEOMETRIC CODE • DIGITS: • 1- major dimension (dia or edge length) • range: 0.8 to 80 inches • < 0.8 rep by 0 and > 80 rep by 9 • 2 - material type • 3 - raw material shape • 4- accuracy • clearance tolerances or surface quality (eg: 32 microinches) • see pages 485 J Cecil IE 590 NMSU

24. OPITZ CODE EXAMPLE • SEE FIGURE 12.7 • CODE: 1 1 1 0 2 • Supplementary code: review part given • code:? J Cecil IE 590 NMSU

25. GT BENEFITS • Coding/classification provide few benefits if it ends there • coding:a means to quantify part geometry, content • One use: to code potential designs before formally designing them • designers sketches a concept, then codes it • using code, similar designs are retrieved from DB • if existing part can be used to satisfy design new design needs, then process ends and time saved • if existing part cant be used, perhaps a variant can be used (simply modify existing design) J Cecil IE 590 NMSU

26. GT BENEFITS • In both cases, no or minimal changes in process plan and production plans may be needed • Many companies have found that they produce identical parts with different names • duplicate tooling, fixtures and engineering time are required when this occurs J Cecil IE 590 NMSU

27. OTHER PROBLEMS • Common characteristic of US industry (Chang) is under-utilization of expensive processing equipment • Takes 2 forms: • Much of the machine time is idle and unproductive • Many of the parts assigned to a specific machine are far below the capacity of the machine • Approach: By grouping closely matched parts into a part family, machines can be more fully utilized from both a scheduling as well as a capacity standpoint J Cecil IE 590 NMSU

28. Application of GT concepts • Major benefit includes part family formation for efficient workflow • Efficient workflow can result from grouping machines logically so that: • material handling and setup can be MINIMIZED • Parts can frequently be grouped so that the same tooling and fixtures can be used: • this enables a major reduction in setup times • Machines can be grouped so that the amount of handling time between machining operations can be minimized J Cecil IE 590 NMSU

29. LAYOUT ISSUES • See figures 12.6 and 12.7 : Process type layout Versus GT based layout • M/c’s are clustered by function Vs M/cs that produce part family form a cell • BASIS FOR GT LAYOUT is part family formation • family formation is based on part features viz. manufacturing features. • No rigid rules for part families ; user sets own definition • General rule: all parts in a family must be related J Cecil IE 590 NMSU

30. Part families • For production flow analysis, all parts in a family must have similar routings • Family size will change depending on criteria • If criteria is: only those parts having exactly the same routing • then few parts will qualify for this family • If criteria is: group all parts requiring a common machine into a family • large part families will result • Before grouping can start, collect info of design and processing of all parts J Cecil IE 590 NMSU

31. Part families • Each part is then rep as a coded form, called an Operation Plan code (OP code) • OP code rep a sequence of operations on a machine and/or a workstation • Eg: DRL01 can rep the sequence: • load the workpiece onto a drill press • attach a drill • drill holes • change the drill to reamer • ream hole & unload workpiece from drill J Cecil IE 590 NMSU

32. Part families • An Operation Plan (OP Plan) is a plan where operations are rep using OP codes • OP codes SIMPLIFIES REPRESENTATION OF PROCESS PLANS • see table 12.7 • Next Focus: Clustering Approach J Cecil IE 590 NMSU