G ROUP T ECHNOLOGY AND C ELLULAR

M ANUFACTURING

(Dr. T. Warren Liao – Louisiana State University)

Group Technology (GT) 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 saving valuable manufacturing time. In GT a large number of parts are classified into different part families based on similarities in their shape, size, holes, threads, and machining operations to improve manufacturing productivity, Fig. 10-3-1. To make GT most effective, the machines necessary to produce the part are grouped into cells where automated work-handling devices provide an efficient flow and processing of parts.

Fig. 10-3-1 In Group Technology, parts are classified into families based on their shape, size, and machining processes. (Modern Machine Shop)

GT is recognized as the key to the integration of all computerized systems in design and manufacturing. It is the common bond that binds CAD (Computer-Aided Design) and CAM (Computer Assisted Manufacturing) together to make possible true CIM (Computer Integrated Manufacturing). It has great appeal to manufacturers because of the cost saving and productivity increases it offers. GT’s advantages apply to computer-aided process planning, retrieval of designs, design and manufacturing standardization, machine tool selection, and long-term planning and analysis.

PART GROUPING

Many components (parts) have a similar shape; therefore one method of grouping parts is by their shape, Fig. 10-3-2. Changing (modifying) an existing part design from the same family can create a new design. Grouping parts into families helps to standardize designs and reduces the possibility of creating too many designs. Therefore, group technology is useful for efficient retrieval of previous designs and to standardize designs.

Fig. 10-3-2 A method of grouping parts into families is by their shape. (OIR/Organization for Industrial Research)

Many parts are produced using the same basic type of machining operation or process, Fig. 10-3-3. A new process plan can be created by changing a standard process plan used by the same family or by changing a process plan used by a particular similar part. Cellular manufacturing is an application of group technology in manufacturing where some of the machines in a manufacturing system are grouped into cells. Each cell is designed for and equipped with the proper tooling and material-handling equipment to produce a specific family of parts. Cellular manufacturing provides a method of obtaining economic advantages in high-variety, low-volume production that are normally associated with low-variety high-Volume production.

Fig. 10-3-3 Parts produced using the same machining process are grouped into families. (OIR/Organization for Industrial Research)

PURPOSE AND ADVANTAGES

Using GT, the features of many parts are examined through the use of interactive computers. While the shape of parts could vary in size, they may contain the same features as smaller parts, Fig. 10-3-4. Parts such as screws, nuts, washers, and gears are easily grouped into classes of similar parts because they are relatively small and have the same features. By grouping parts into families, such as rotational and prismatic parts, manufacturing productivity can be improved because all require similar operations or manufacturing processes, Fig. 10-3-5. This improves process planning and the scheduling of machines and equipment.

Fig. 10-3-4 A wide variety of parts are found in most manufacturing plants. (Computervision Corp.)

Fig. 10-3-5 The same parts in Fig. 10-3-4 are grouped into part families on the basis of similarities. (Computervision Corp.)

Part-coding and standardization improves the material-handling and manufacturing process, resulting in more efficient use of machine tools and related equipment. This is accomplished through the use of interactive computer programs that classify and assign codes to the parts based on the design features and manufacturing operations.

GT is also valuable for product design because it reduces lead times associated with engineering, production planning, and fabrication, creating cost savings of 10% or higher. It formerly took a person hours to look over a few thousand prints searching for a part that would lend itself to a particular operation. Using GT, this job can be completed in a few minutes by studying the reports of a computerized group technology system. As the process is fully developed, other departments such as purchasing, testing, and quality control, should also use the same information in the classification and coding system to reduce their costs.