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IE 590 INTEGRATED MANUFACTURING GROUP TECHNOLOGY. CAM-I Automated Process Planning System. One of the most well-known systems is the CAM-I Automated Process Planning (CAPP) system

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cam i automated process planning system
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

slide3

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

variant process planning systems vpps
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

variant process planning systems vpps1
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

vpps contd
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

vpps contd1
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

part coding systems and issues
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

part coding systems and issues1
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

part families
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

part families1
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

group technology
GROUP TECHNOLOGY

Please refer to chapter 13 of CAM book

J Cecil IE 590 NMSU

group technology gt
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

slide14

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

slide15

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

coding and classification
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

hierarchical or monocode
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

chain or polycode
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

hybrid code
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

further readings
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

the opitz code
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

geometric code
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

supplemental code
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

opitz code example
OPITZ CODE EXAMPLE
  • SEE FIGURE 12.7
  • CODE: 1 1 1 0 2
  • Supplementary code: review part given
    • code:?

J Cecil IE 590 NMSU

slide25

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

slide26

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

slide27

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

application of gt concepts
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

layout issues
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

part families2
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

part families3
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

part families4
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

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