group technology (gt)

7/30/2019 Group Technology (GT)

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Group Technology (GT) It is an approach to organizing manufacturing which can be applied

to any industry where a small batch variety production is used.

It is a basic & simple concept of :

identification & bringing together related or similar parts & processed,to take advantage of the similarities which exists,

during all stages of design & manufacture.

It is based on the fact that :

small lots of different parts can be produced more economically,

if they are grouped & scheduled for productionaccording to the common characteristics.

Definition :

1. It is an approach to the organization of work in which organizationalunits are relatively independent groups, each responsible forproduction of a given family of products.

2. A group is a combination of a set of workers & a set of machines & orother facilities in one reserved area, designed to complete a specifiedset of products.

3. A family is the set of products produced by a group.

( 405 MT / kackar)


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Group Lay out.

With the line lay out, machines or workstations are arranged in a line in

their sequence of operation.

It is preferred when all the components made on the line use the same

workstations in the same sequence.

When line layout cannot be used, machines & workstations are used to

process the parts in batches & the facilities are arranged w.r.t functions.

New method of facility layout called GT is based on product specialisation

in which group of machines chosen for each family are situated together in

a group layout in such a way that parts flow from one machine to the nextin sequence of operation. It is not necessary for every part to visit each

machine but machines in a group or cell should ideally be capable of

carrying out all operations required in the family.

Gr IV D,E

Gr III C,F

Gr II B,G

Gr I A,H

Facilities

Group Layout405-6 MT / Kackar


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Desirable characteristics of Group1. There should be group of workers special to the group:

Workers associated with a specific group make a good team & they learn

to understand the special problems associated with machines &

equipments & with the family of components which they make.Workers should not be allowed to move or transferred out of the group.

2 There should be group of machines & equipments special to each group:The group should be supplied with machines that are needed to processall the components in their families. The parts should not move out of the

group for operations on machines belonging to other groups. This helps toreduce throughput time, W.I.P. inventory, & handling time.

3 Special allocated area to house machines & equipment:

This is an essential characteristics if full benefit of GT is to be obtained.

4 Group should have its own special products to be completed.

5 A common output target for the group:This is essential if full advantage is to be taken of the use of plannedsequence of loading to reduce set-up times & throughput times

& to increase machine capacity.

6 The number of workers in the group should be small.

( 406 MT / Kackar)


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Benefits of Groups

1. Reduction of throughput time as all operations on a part are done inside

the group.

2. Decrease in w.i.p inventory.

3. Improvement in quality levels.

4. Completion of work as per due date or schedule.

5. Reduced set-up time hence increase in productive capacity.

Stages in group technology manufacture:

1. The parts of each of the items produced areexamined & placed into logical classes or families

& the operation sequence for each class of parts

is determined & specified.

2 Groups of facilities, suitable for processing of these classes of partsare specified using the operation planning details of

forecasted demand for the items & hence components.

3 The sequencing of each class of parts for each group of facilities.

(406 MT / Kackar)


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Stages in group technology manufacture: contd.

a) Formation of part families:

- A family is the collection of parts which are similar for purpose of manufacture.

Usually they are related by size, geometry, shape& required similar manufacturing operations.

- The key factor in using GT successfully is the ability to identify readily items

within the same family.

1 Coding & classification system:

4-systems are commonly used for classification.

i) British system ii) Mitrofanov system iii) Optive system iv) Vuoso system

2 Production flow analysis:

- This technique was derived by Burbidge (1975) to enable groups of parts

to be defined in terms of the operations that they will require for theirmanufacture.

- Major groups are formed using factory flow analysis on the basis similar

operation route sequence. Continued - next slide


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Formation of part families: contd.

Production flow analysis has 3- stages:

a) Factory flow analysis: This is concerned with the

(i)1st

major division into large groups of department size &(ii) into very large families of parts to be made in to these departments.

b) Group analysis : This is concerned with the

(i) division of plant assigned to each department, on to groups &

(ii) division of parts into associated families.

The primary aim is to achieve the simplest possible material flow systeminside each department & to help to achieve this,

3-secondary aims are adopted. (i) As far as possible, each part should be

processed in one group only, (ii) each machine type should exist in eachgroup only & (iii) incompatible processes should be in different groups.

c) Line analysis: This is concerned with theflow of materials between machines inside the groups &

planning the best layout for the machines.

The aim is to find the sequence of machines which will give the nearestapproximation to line flow.

Continued - next slide


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Formation of part families: contd.3 Cluster analysis:

Clustering is the science of classification of objects based upon their

possession or lack of defined characteristics.

This approach provides the way to study similarities between a divers

population of objects in a quantitative manner.

This involves 3-stages:

i) Preparation of part operation matrix:

This indicates if the features are either present or absent.ii) Prepare a similarity co-efficient matrix: This is based on

the extent to which the parts share common characteristics.

iii) Perform a cluster analysis :

The similarity between each pair of objects is examined &

group of objects are formed such that within each group

the objects are similar to each other according to set of rules.


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b) Choice of family:

Composition of family parts which are housed in a group is largelydetermined by the equipments available within the organization.

4-aspects of the group likely to result from the family should be examined:

i) What load will the family generate?

ii) What capacities & capabilities would be needed?

iii) Is it possible to set up the group for the family?

iv) Are the necessary machines available or to be obtained?

c) Composite Components:

Once the family has been identified , a composite component may be

conceptualized. It is the one which contains all of the features of all the

members of the family. ( refer figure in next slide408 / MT).

The available machines are then surveyed to find which group can be

best put together to produce the family.



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d) Facilities sequencing:

The facilities necessary to perform all operations on the part family & theexpected load on each equipment can be listed for each family identified.

Singleton outlined a simple method for determining a layout sequence

foe a number of operations or machines through which a variety of parts

is processed, each part having a particular route through the operation.

Travel or cross charts are some times used in developing layouts.Such charts show the nature of the inter-operation movements for all

parts for a given period of time.

e) Sequencing :

Determination of sequence in which the batches of parts are loaded on

to the GT cell or Line will be influenced by the desire to minimise theset-up time/cost& minimise throughput time


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Stages in group technology manufacture: contd.f ) Introducing group technology:

Introduction of GT may affect wide areas of the organization depending on

the extent to which it is applied. Considerable preparatory effort is required including training of staff to get

acceptance of the accepted change over.

New procedures in production planning & control are needed if theadvantage of the GT are to be realized fully.

g) Benefits of GT:1. Reduced unit set-up time & increased capacity.

2. Improved labour efficiency resulting from standardization & simplification.

3. Simplification of material flow system.

4. Simplifies production control & material handling.

5. Reduction in throughput time.6. Reduced work-in-process

7. Simplification in planning procedures.(408 MT / kackar)

group technology (gt)

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