Introduction to Group Technology

by Andhika Dinata dan Ade Febriansyah

Abstract
Recently, batch manufacturing is estimated to be the most common production
that constitutes for about 50% or more of the total manufacturing activity. Based
on it, there is growing need to make batch more efficient. One of the approaches
that related to that objective is by using Group Technology (GT) concepts. GT is
a manufacturing philosophy that attempts to group products with similar design
or manufacturing characteristics. Indeed, GT even gained importance in a way of
worker effectiveness with the cellular design application. GT also attempts to
improve material flows (refer to; backtracking reduction, intersection reduction)
in order to get higher utilization of labor and equipment.
Keywords: Group Technology, higher utilization

1. Introduction
Group Technology is an approach that seeks to identify those attributes of
a population that permit its members to be collected into groups, which are
called families. There are usually efficiencies and advantages to be gained
from dealing with the population when it is divided into groups. Similar
parts are arranged into group (part families). For example, a plant
producing 10,000 different part numbers may be able to group of these
parts into 50 or more distinct families. In fact, the processing of each parts
of a given family would be similar in term of manufacturing efficiencies.
These efficiencies are achieved by arranging the production equipment
into machine groups or cells, to facilitate work flow.
Originally, the biggest single obstacle in changing over to group
technology form a traditional production shop is the problem of grouping
parts. According to general researches, there are three methods which are
usually used for solving that problem. The three methods are : (1) Visual
inspection, (2) Classification and coding parts, and (3) Production flow
analysis.
2. A Definition of Group Technology
Group Technology is a management philosophy that attempts to group
products with similar design or manufacturing characteristics [1]. In
similar view, Groover has been defined Group Technology as a
manufacturing philosophy in which similar parts are identified and
grouped together to take advantage of their similarities in manufacturing
and design [2]. An application of GT is cellular manufacturing design
(CM) that involves grouping machines based on the parts manufactured by
them. The main objective of CM is to identify machine cells and part
families simultaneously, and also to allocate part families to machine cells
in a way that minimizes the intercellular movement of parts [2].
CM is a relatively recent concept that has been applied successfully in
many manufacturing environments can achieved significant benefits. The
surveyed Wemmerlov and Hyer (1989) have witnessed these goals of GT
with [2] :
Ø Set up time reduction
Ø Work-in-process inventory reduction
Ø Direct and indirect labor cost reduction
Ø Improvement in quality
Ø Improvement in material flow
Ø Improvement in machine utilization
Ø Improvement in space utilization
Ø Improvement in employee morale.
3. Part Families
A part family means that a collection of parts which are similar either
because of geometric shape and size or because similar processing steps
are required in their manufacture [1]. The parts within a family are
different, but their similarities are close enough to merit their identification
as members of the part family.















Figure 3.1 Two parts of identical shape and size and size but different
manufacturing requirements
Figure 3.2 Thirteen parts with similar manufacturing process requirements but different
design attributes

Figures 3.1 and 3.2 show two parts families. The two parts shown in figure
3.1 are similar from a design viewpoint but quite different in terms of
manufacturing. Figure 3.2 might constitute a part family in manufacturing,
but their geometry characteristics do not permit them to be grouped as
design parts family.

As a principle, GT are arranged the various machine tools by specific
function. There is a lathe, milling, drill press, and so on. During the
machining of a given part, the workpiece must be moved between sections
with perhaps the same section being visited several times. This results in a
significant amount of material handling, a large in-process inventory,
usually more setups than necessary, long manufacturing lead time, and
high cost.







Figure 3.4 Group Technology Layout

Figure 3.4 shows a production shop of equivalent capacity, but with the
machines arranged into cells. Each cell is organized to specialize in the
manufacture of a particular part family. Advantages are gained in the form
of reduced workpiece handling, lower set up times, less-in process
inventory, and shorter lead times. Continuously, some of the
manufacturing cells can be designed to form production flow lines, with
conveyors used to transport work parts between machines in the cell.
4. Conclusions
GT are commonly known as a manufacturing philosophy that attempts to
group products with similar design or similar manufacturing
characteristics. CM can be identified as an application of GT that involves
grouping machines based on the parts manufactured by them. Recently,
GT plays important roles for production, especially for improving material
flows, resources utilization, etc.

References
[1] Groover, Mikhell P. 1987. Automation, Production Systems, and Computer
Integrated Manufacturing. Prentice Hall International: USA.
[2] Heragu, Sunderesh. 1997. Facilities Design. PWS Publishing Company:
Boston.