Transcript Group Technology - Management & Development Center-Home

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
HIGH
VOLUME
TRANSFER
LINE
SPECIAL
SYSTEM
FLEXIBLE
MANUFACTURING
SYSTEM
MANUFACTURING
Cells
STD. AND GEN.
MACHINERY
LOW
HIGH
VARIETY
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.
DATA
PROCESSING
DESIGN
ENGINEERING
MAINTENANCE
INVENTORY
TOOL
ENGINEERING
PLANNING
ESTIMATING
PURCHASING
INDUSTRIAL
RELATIONS
ASSEMBLY
QUALITY
CONTROL
MANAGEMENT
MFG.
ENGINEERING
R&D
COST
ACCOUNTING
SALES
GT
SHIPPING &
RECEIVING
Three Techniques To Form Part Families
1. Tacit judgment or visual
inspection
• May use photos or part
prints
• Utilizes subjective
judgment
2. Production Flow Analysis
• 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
Part Mfg. Attributes
Basic external shape
Basic internal shape
Material
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
MAPPING FROM POPULATION
SPACE TO CODE SPACE
POPULATION
SPACE
H
P
CODE
SPACE
C
Hierarchical Structure
32XX
321X
Mechanical
3231
Transmission
323X
322X
3221
UNF thread
3232
322
2
3223
3233
Hybrid Structure
Polycode
Monocode
Polycode
Reduction Of Mfg. Costs By Various
Steps Of Group Technology Applications
(Adapted From Ham442)
Not All Cost Savings Are Immediate...
Improvements in Engineering Design
Materials Management & Purchasing Benefits
Production Control Benefits
Manufacturing Engineering Benefits
Tooling & Setup Benefits
Management Benefits
Overall Cost Reduction &
Increased Productivity
0
6
12 18 24 36
Time (months)
• Proliferation Of Parts
Selection of optical instrument parts in one company,
Illustrating the similarity between certain components
• Note: some of the above are almost the same
Conceptual design
Design concept can be coded.
Code is a rough model of the
conceptual design.
Coding (rough model)
Retrieval existing designs
Design
archive
Existing designs
Design modification
New Design
Retrieve designs of similar
shape or function and use
them as the examples.
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
Drilling
Milling
Lathe
L
L
M
M
L
L
M
M
D
D
D
D
Grinding
L
L
M
M
Assembly
L
L
A
A
Receiving and
Shipping
A
A
PROCESS-TYPE LAYOUT
G
G
G
G
G
G
Group Technology Layout
L
L
M
D
G
A
Receiving
L
L
M
M
D
G
A
G
Shipping
Cellular Layout
Department #2
D
D
Department #1
M
I
D
I
L
Department #3
L
L
D
M
M
I
M
2nd Digit
main shape
0
2
3
Rotational
1
3rd Digit
rotational
machining
5th Digit
4th Digit
additional
plane surface holes teeth &
matching
forming
External
shape
element
Internal
shape
element
Machining
of plane
surfaces
Other holes
and teeth
Main shape
Rotational
machining
Machining
of plane
surfaces
Other holes
teeth and
forming
Main bore
& rotational
machining
Machining
of plane
surfaces
Other holes
teeth and
forming
4
5
6
7
8
9
Special
Non-rotational
Positions
with a
digit
Form Code
Main shape
Main shape
Main shape
Special
Supplimentary
code
Digit
6 7 8 9
Dimensions
Material
Original shape of raw materials
Accuracy
1st Digit
part class
Opitz coding and classification system.
(Reprinted with permission from H. Opitz, A
Classification System to Describe Workpieces, Pergamon Press.)
Engineering
drawing
Typical
Process
Planning
System
Process
planner
XX
X
Process planning
system
Code or
other form
of input
Process
Industrial engineer
• Time standard
• Operation
instruction
• Layout
Part
programmer
APT Program
APT Processor
& post-processor
Production planner
• Scheduling
• MPP
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)
Process planning bridges design and
manufacturing
Bridge
Design
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
1. Preparatory Stage Of
Variant
Process Planning
Part Drawing
Coding
Family One
Standard
Plan
File
Family Formation
Process Plan
(Indexed
by Family
Matrix)
2. Production Stage Of Variant
Process Planning
Coding
Family Search
Process Plan
Editing
Standard
Plan
Retrieval
Standard
Plan
File