Computer aided manufacturing. Useful for mechanical and production engineering students.

1. GROUP TECHNOLOGY

2. Group

3. Group Technology
• It is technology in which similar parts are
identified and grouped together to take advantage
of their similarities in Design & achieve the
effectiveness. (Production)
• Parts in the medium production quantity range are
usually made in batches.
• GT exploits the part similarities by utilizing
similar processes and tooling to produce them
• GT can be implemented by manual or automated
techniques
• When automated, the term flexible manufacturing
system is often applied.

4. Design Group:

5. Group Production Lines

6. G.T.>>
• Similarities? among parts permit them to be
classified into part families
• In each part family, processing steps are
similar
• The improvement is typically achieved by
organizing the production facilities into
manufacturing cells that specialize in
production of certain part families

7. Part Family

8. Part Families
• Part families are a central feature of group
technology
• A group of parts that possess similarities in
geometric shape and size, or in the processing
steps used in their manufacture.
• There are always differences among parts in a
family But the similarities are close enough
that the parts can be grouped into the same
family.

9. Two parts that are identical in shape and size but quite
different in manufacturing:
(a)1,000,000 units/yr, tolerance = ±0.010 inch, 1015 CR
steel, nickel plate
(b)100/yr, tolerance = ±0.001 inch, 18-8 stainless steel

10. Part Families:
• Ten parts that are
different in size and
shape, but quite similar
in terms of
manufacturing
• All parts are machined
from cylindrical stock by
turning; some parts
require drilling and/or
milling

11. Cellular Engineering

12. Typical Layout Of Cell

13. Advantages in Cellular Engg.
• Reduction in transportation.
• Set up time is low.
• Less in process inventory.
• Shorter lead time
• Effective utilization of machines.

14. Ways to Identify Part Families:
• Visual inspection - using
best judgment to group
parts into appropriate
families, based on the
parts or photos of the
parts
• Production flow analysis -
using information
contained on route sheets
to classify parts
• Parts classification and
coding - identifying
similarities and differences
among parts and relating
them by means of a
coding scheme

15. 1. Parts Classification and Coding
Most classification and coding systems are one
of the following:
1) Systems based on part design attributes
2) Systems based on part manufacturing
attributes
3) Systems based on both design and
manufacturing attributes

16. Parts Classification and Coding
Part Design Attributes
• Major dimensions
• Basic external shape
• Basic internal shape
• Length/diameter ratio
• Aspect Ratio (L/W)
• Material type
• Part function
• Tolerances
• Surface finish
Part Manufacturing Attributes
• Major process
• Operation sequence
• Batch size
• Annual production
• Machine tools
• Cutting tools
• Material type

17. Three structures used in classification
and coding schemes
• Hierarchical structure, known as a mono-code, in
which the interpretation of each successive
symbol depends on the value of the preceding
symbols. For e.g. 15 & 25
• Chain-type structure, known as a polycode, in
which the interpretation of each symbol in the
sequence is always the same; it does not depend
on the value of preceding symbols
• Mixed-mode structure, which is a hybrid of the
two previous codes

18. Some of the important systems
• Opitz classification system –the University of Aachen
in Germany, nonproprietary, Chaintype.
• Brisch System –(Brisch-Birn Inc.)
• CODE (Manufacturing Data System, Inc.)
• CUTPLAN (Metcut Associates)
• DCLASS (Brigham Young University)
• MultiClass (OIR: Organization for Industrial Research),
hierarchical or decision-tree coding structure
• Part Analog System (Lovelace, Lawrence & Co., Inc.)

19. Optiz System
• This Part classification & coding was developed
by H.Opitz.
• 12345 6789 ABCD.
• Digit 1 to 5 = Form Codes
• Digit 6 to 9 = Supplementary Codes
• A,B,C,D = Secondary Codes intended to identify
the Sequence & production operations.
• Secondary Codes can be designed by user as per
need

20. Basic Structure of the Opitz Parts Classification
and Coding System

21. Basic structure of the Opitz system of parts classification and
coding

22. Coding :
Given the part design shown define the "form
code" using the Opitz system.

23. Steps
• Step 1: The total length of the part is 1.75, overall
diameter 1.25,
L/D = 1.4 (code 1)
• Step 2: External shape - a rotational part that is stepped
on both with one thread
(code 5)
Step 3: Internal shape - a through hole
(code 1)
Step 4: By examining the drawing of the part
(code 0)
Step 5: No auxiliary holes and gear teeth
(code 0)

24. MultiClass(MClass) –developed by the Organization for Industrial
Research (OIR)
• It is ranging from 12 to 30 digits.
• First 12 are UNIVERSAL CODE
Applied to any part.
Next 18 digits are Supplementary code
It can be used to particular industry i.e. Lot size,
piece time, cost data, sequence.

25. First 18 digits of the Multiclass Classification and
Coding System

26. Production Flow Analysis
• It is a process in which part families are
identified & associated machine group,
That uses the information contained on
production route sheets rater than part
drawing.
Similar routings are classified into part families.
These can be used to form machine cells in GT
layout.

27. The procedure of Production flow analysis (PFA)
consists of the following steps:
• Data Collection
• Sortation of process routings
• PFA Chart
• Cluster Analysis

28. 1. Data Collection
• The minimum data needed in the analysis are
the part number and operation sequence,
which is obtained from process plans.
• Each operation is related with particular
machine.

29. 2 Sortation of process plans.
• A sortation procedure
is used to group parts
with identical process
plans.
• Machines are operated
in code no.
• This procedure is used
to arrange these parts
into PACKS
Machine Tools Code No
Cut Of 01
Lathe 02
Turret Lathe 03
Mill 04
Drill 05
NC-Drill 06
Grinding 07

30. 3.PFA Chart. The processes is used for each group (Pack) are
then displayed in a PFA chart as shown below.

31. 4. Clustering Analysis. From the pattern of data in the PFA chart,
related groupings are identified and rearranged into a new
pattern that brings together groups with similar machine
sequences.

32. Benefits
• Product Engineering:
Reduce Part Proliferation (Reproducing)
Help design Standardization
Provide Mfg. Feedback
• Manufacturing Engineering
Process & tool selection, m/c purchase, MH
• Production Engineering
Reduce lead time, reduce delays, reduce set
times, improve product quality

33. <<<<……>>>>>
• Production & planning control:
Group scheduling, stock accounting, improve
product design.
• Other:
Increase productivity, improved accuracy in
estimation of cost, reduce cost purchasing,
Improved plant efficiency