The Background and Conception of GT
Mass production was considered to be a virtue in the 1960s and 1970s, but this situation changed during the 1980s. Multi-product, small-lot-sized production gradually became the preference from 1980s, and to date the mass customization of products has become an effective manufacturing mode for enterprises to seize the advantage in a strongly competitive environment. Applying the traditional means of production to multi-product, small-lot-size production and mass customization of products incurs many difficulties, such as complexities of organization and managment, difficulties of production planning and scheduling, as well as limitation of the application of advanced technology. To cope with these difficulties, several effective approaches have been developed. Of these approaches, and in addition to flexible manufacturing and standardization, simplification, and specialization of production, GT plays an important role in multi-product, small-lot-sized production and mass customization of products. There have been many applications of GT in the process of production, from design and planning to the organization of manufacturing facilities. In practice, GT provides a link between design and manufacturing. Various countries demonstrated different interests in GT in the early research, for example, the focus in Russia was on the grouping of parts for processing on single machines, mainly to rationalize tooling and to reduce resetting times; in the UK and Germany, the greatest emphasis has been on the development of cellular layout and group flow line; in Japan, concentration was not only on developing classification systems and group layouts, but has also extended the basic approach to flexible manufacturing systems; in the U. S. A., emphasis has been placed on component analysis and associated data processing (Gallagher, 1986). However, what is the definition of GT? Shunk defines GT as a disciplined approach to identifying things such as parts, processes, equipment, tools, people, or customer needs by their attributes and looking for similarities between and among the things: grouping the things into families according to similarities; and, finally, increasing the efficiency and effectiveness of managing the things by taking advantage of the similarities (Shunk, 1985).
The application of GT results in acquiring the advantages of multi-product batch manufacturing in the small-lot-sized production and the mass customization of products. With the advent and development of CIMS (Computer Integrated Manufacturing System), GT become the bridge to span CAD (Computer-Aided Design), CAPP (Computer-Aided Process Planning), and CAM (Computer-Aided Manufacturing). GT has now become a kind of production technology science, which takes full advantages of similarities of parts in the process of production to increase production efficiency, viz., the similar approaches are used to fabricate the part families formed by grouping similar parts. The crux of GT is concerned with how to identify and explore the similarities, and to reduce the time and cost of manufacturing by the sharing solutions presented. GT is a concept for increasing production efficiency by grouping various parts and products with similar design and/or production process (Ham, 1985). It is also an approach to organizing production or a manufacturing philosophy. The philosophy of GT has been used to small-batch variable production. The criterion has been applied in many fields including machining, welded fabrications, foundry work, presswork, forging, and plastic injection moulding. The basic approach enables all aspects of manufacturing, from design, through estimating and planning to production, to be rationalized (Gallagher, 1986). The overall advantages have been summarized by Andrew Kusiak (Kusiak, 1990). The main advantages are as follows.
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Reduced production lead time (20-88%).
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Reduced work-in-process (up to 88%)
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Reduced labor (15-25%)
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Reduced tooling (20-30%)
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Reduced rework and scrap materials (15-75%)
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Reduced setup time (20-60%)
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Reduced order time delivery
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Improved human relations
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Reduced paper work
From the birth of GT to the present has been about 60 years. During this time, GT has been laying one of the foundations for the application of computer-aided technology in manufacturing. The application of GT in manufacturing changes the paradigms of management and the modes of processing.