Group Technology

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Chapter 12 GROUP TECHNOLOGY by Dr. Richard A.
Wysk
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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.
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• 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"

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• WHY GROUP TECHNOLOGY?
• AVERAGE LOT SIZE DECREASING
• PART VARIETY INCREASING
• INCREASED VARIETY OF MATERIALS
• WITH DIVERSE PROPERTIES
• REQUIREMENTS FOR CLOSER
• TOLERANCES

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HIGH
FLEXIBILITY
TRANSFER LINE
PRODUCTION CAPACITY
SPECIAL SYSTEM
FLEXIBLE MANUFACTURING SYSTEM
VOLUME
MANUFACTURING Cells
STD. AND GEN. MACHINERY
LOW
HIGH
VARIETY
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EVERYDAY EXAMPLES 1. FAST FOOD CHAINS 2.
DOCTORS, DENTISTS AND ALSO MANUFACTURING
A FAMILY OF PARTS
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PRODUCTION FAMILY
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• LACK OF COMMON DATABASE FOR
• MFG., DESIGN...

• DONT REDESIGN THE WHEEL
• AUTOMATED PROCESS PLANNING
• DATABASE TO DRIVE THE
• AUTOMATED FACTORY

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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
Contd
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OTHER BENEFITS OF GROUP TECHNOLOGY EASIER TO
JUSTIFY AUTOMATION STANDARDIZATION IN DESIGN
DATA RETRIEVAL EASIER, MORE STANDARDIZED
PROCESS PLANS INCREASES IN QUALITY
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GT AFFECTS MOST EVERY OPERATING AND STAFF
FUNCTION. IT IS MORE THAN MERELY A TECHNIQUE,
BUT A TOTAL MANUFACTURING PHILOSOPHY.
DESIGN ENGINEERING
DATA PROCESSING
SALES
MAINTENANCE
INVENTORY
TOOL ENGINEERING
PLANNING
ESTIMATING
PURCHASING
INDUSTRIAL RELATIONS
ASSEMBLY
QUALITY CONTROL
MANAGEMENT
MFG. ENGINEERING
R D
COST ACCOUNTING
SHIPPING RECEIVING
GT
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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

Contd
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(No Transcript)
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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
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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
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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

contd
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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
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MAPPING FROM POPULATION SPACE TO CODE SPACE
POPULATION SPACE
H
P
CODE SPACE
C
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HIERARCHICAL STRUCTURE
32XX
Hydraulic
Electrical
321X
323X
Mechanical
Power
Receiving
Transmission
322X
3232
UNC thread
No thread
UNF thread
3222
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(No Transcript)
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REDUCTION OF MFG. COSTS BY VARIOUS STEPS OF
GROUP TECHNOLOGY APPLICATIONS (ADAPTED FROM
HAM442)
NOT ALL COST SAVINGS ARE IMMEDIATE...
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• 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

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GT FOR DESIGN APPLICATION
Design concept can be coded. Code is a rough
model of the conceptual design.
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.
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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
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EXAMPLE
THIRTEEN PARTS WITH SIMILAR MANUFACTURING
PROCESS REQUIREMENTS BUT DIFFERENT DESIGN
ATTRIBUTES
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FUNCTIONAL LAYOUTS ARE INEFFICIENT
Milling
Drilling
Lathe
D
D
L
M
L
M
D
D
L
L
M
M
Grinding
G
L
L
M
G
M
Assembly
G
G
L
L
A
A
G
G
A
Receiving and Shipping
A
PROCESS-TYPE LAYOUT
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GROUP TECHNOLOGY LAYOUT
G
D
L
M
A
A
Receiving
D
M
Shipping
L
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CELLULAR LAYOUT
Department 2
Department 1
D
D
M
I
D
I
L
Department 3
M
M
D
L
L
M
I
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FORM CODE
1st Digit part class
5th Digit additional holes teeth forming
3rd Digit rotational machining
4th Digit plane surface matching
2nd Digit main shape
Positions with a digit
0
1
2
Rotational
3
4
5
Special
6
7
Non-rotational
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Opitz coding and classification system.
(Reprinted with permission from H. Opitz, A
Classification System to Describe Workpieces,
Pergamon Press.)
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Special
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Engineering drawing
TYPICAL PROCESS PLANNING SYSTEM
Process planner
Code or other form of input

• Industrial engineer
• Time standard
• Operation
• instruction
• Layout

• Production planner
• Scheduling
• MPP

Part programmer
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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
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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)
Contd
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1. PREPARATORY STAGE OF VARIANT PROCESS
PLANNING
Part Drawing
Coding
Family One
Standard Plan File
Family Formation
(Indexed by Family Matrix)
Process Plan
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2. PRODUCTON STAGE OF VARIANT PROCESS PLANNING
Family Search
Coding
Standard Plan File
Process Plan
Standard Plan Retrieval
Editing