Ie 590 integrated manufacturing group technology
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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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IE 590 INTEGRATED MANUFACTURING GROUP TECHNOLOGY

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Ie 590 integrated manufacturing group technology

IE 590 INTEGRATED MANUFACTURINGGROUP TECHNOLOGY

J Cecil IE 590 NMSU


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


Ie 590 integrated manufacturing group technology

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


Ie 590 integrated manufacturing group technology

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


Ie 590 integrated manufacturing group technology

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


Ie 590 integrated manufacturing group technology

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


Ie 590 integrated manufacturing group technology

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


Ie 590 integrated manufacturing group technology

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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