1. Chapter 12
GROUP TECHNOLOGY by
Dr. Richard A. Wysk

2. 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.

3. First book formalize the concept:
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"

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

5. VOLUME VARIETY HIGH FLEXIBILITY TRANSFER PRODUCTION CAPACITY LINE
SPECIAL
SYSTEM
FLEXIBLE
MANUFACTURING
SYSTEM
VOLUME
MANUFACTURING
Cells
STD. AND GEN.
MACHINERY
LOW
HIGH
VARIETY

6. AND ALSO MANUFACTURING
EVERYDAY EXAMPLES
1. FAST FOOD CHAINS
2. DOCTORS, DENTISTS
AND ALSO MANUFACTURING
A FAMILY OF PARTS

7. PRODUCTION FAMILY

8. LACK OF COMMON DATABASE FOR
MFG., DESIGN...
DON’T “REDESIGN THE WHEEL”
AUTOMATED PROCESS PLANNING
DATABASE TO DRIVE THE
AUTOMATED FACTORY

9. 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

10. OTHER BENEFITS OF GROUP TECHNOLOGY
EASIER TO JUSTIFY AUTOMATION
STANDARDIZATION IN DESIGN
DATA RETRIEVAL
EASIER, MORE STANDARDIZED PROCESS PLANS
INCREASES IN QUALITY

11. GT 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 GT
SHIPPING &
RECEIVING

12. 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

13. 3. CLASSIFICATION AND CODING
CODES GEOMETRY/DESIGN AND MFG.
INFO ABOUT A COMPONENT
CODES ARE ALPHANUMERIC STRINGS
EASIER TO USE FOR OTHER ANALYSES

14. 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.
3. SYSTEMS BASED ON DESIGN AND MFG.

15. LENGTH/DIAMETER RATIO TOLERANCES-----MACHINE TOOL
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

16. 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

17. 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

18. MAPPING FROM POPULATION
SPACE TO CODE SPACE
POPULATION
SPACE H P
CODE
SPACE C

19. HIERARCHICAL STRUCTURE
32XX
Hydraulic
Electrical
3231
3233
321X
323X
Mechanical
Power
Receiving
Transmission
322X
3232
No thread
UNC thread
UNF thread
3221
3223
3222

20. Monocode
Polycode
HYBRID STRUCTURE

21. 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
Time (months)

22. PROLIFERATION OF PARTS NOTE: SOME OF THE ABOVE ARE ALMOST THE SAME
SELECTION OF OPTICAL INSTRUMENT PARTS IN ONE COMPANY,
ILLUSTRATING THE SIMILARITY BETWEEN CERTAIN COMPONENTS
NOTE: SOME OF THE ABOVE ARE ALMOST THE SAME

23. 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.

24. 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

25. THIRTEEN PARTS WITH SIMILAR MANUFACTURING
EXAMPLE:
THIRTEEN PARTS WITH SIMILAR MANUFACTURING
PROCESS REQUIREMENTS BUT DIFFERENT
DESIGN ATTRIBUTES

26. FUNCTIONAL LAYOUTS ARE INEFFICIENT
Lathe
Milling
Drilling L L M M D D D D L L M M
Grinding L L M M G G
Assembly L L G G A A
Receiving and
Shipping G G A A
PROCESS-TYPE LAYOUT

27. GROUP TECHNOLOGY LAYOUTM D G A A
Receiving L M G L M D
Shipping

28. CELLULAR LAYOUT Department #2 Department #1 D D M I D I L

29. Original shape of raw materials
FORM CODE
1st Digit
part class
5th Digit
additional
holes teeth &
forming
Supplim-
entary
code
Digit
Original shape of raw materials
Dimensions
Material
Accuracy
2nd Digit
main shape
3rd Digit
rotational
machining
4th Digit
plane surface
matching
Positions
with a
digit
External
shape
element
Main shape
Internal
shape
element
Rotational
machining
Main bore
& rotational
Machining
of plane
surfaces
Other holes
and teeth
teeth and
forming 1 2
Rotational 3 4 5
Special 6 7
Non-rotational 8
Opitz coding and classification system.
(Reprinted with permission from H. Opitz, A
Classification System to Describe Workpieces, Pergamon Press.) 9
Special

30. TYPICAL PROCESS PLANNING SYSTEM
Engineering
drawing
TYPICAL
PROCESS
PLANNING
SYSTEM
Process
planner
Code or
other form
of input
XXX
Process planning
system
Process
Industrial engineer
Time standard
Operation
instruction
Layout
Production planner
Scheduling
MPP
Part
programmer
APT Program
APT Processor
& post-processor

31. Process planning bridges design and
“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

32. 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

33. 1. PREPARATORY STAGE OF VARIANT PROCESS PLANNING
Part Drawing
Coding
Family One
Standard
Plan
File
Family Formation
(Indexed
by Family
Matrix)
Process Plan

34. 2. PRODUCTON STAGE OF VARIANT
PROCESS PLANNING
Coding
Family Search
Standard
Plan
File
Process Plan
Editing
Standard Plan
Retrieval