A part family is a collection of parts which are similar either because of geometric shape and size or because similar processing steps are required in their manufacture. The parts within a family are different, but their similarities are close enough to merit their identification as members of the part family.
Parts classification and coding
This method of grouping parts into families involves an examination of the individual design and/or manufacturing attributes of each part. The attributes of the part are uniquely identified by means of a code number. This classification and coding may be carried out on the entire list of active parts of the firm, or a sampling process may be used to establish the part families. For example, parts produced in the shop during a certain given time period could be examined to identify part family categories. The trouble with any sampling procedure is the risk that the sample may be unrepresentative of the entire population. However, this risk may be worth taking, when compared to the relatively enormous task of coding all the company’s parts.
Parts classification and coding systems divide themselves into one of three general categories:
1. Systems based on part design attributes
2. Systems based on part manufacturing attributes
3. Systems based on both design and manufacturing attributes
The types of design and manufacturing parts attributes typically included in classification schemes are listed in Table 1.
Group technology machine cells
The traditional view of group technology includes the concept of GT machine cells-groups of machines arranged to produce similar part families. This cellular arrangement of production equipment is designed to achieve an efficient workflow within the cell. It also results in labor and machine specialization for the particular part families produced by the cell.
Part families are defined by the fact that their members have similar design and manufacturing attributes. The composite part concept takes this part family definition to its logical conclusion. It conceives of a hypothetical part that represents all of the design and corresponding manufacturing attributes possessed by the various individuals in the family. Such a hypothetical part is illustrated in the following Figure.
Benefits of group technology
Although group technology is expected to be an important principle in future production plants, it has not yet achieved the widespread application, which might be expected. There are several reasons for this. First, there is the problem of rearranging the machines in the plant into GT cells. Second, there is the problem of identifying part families among the many components produced in the plant. Finally, it is common for companies to encounter a general resistance among its operating personnel when changeover to a new system is contemplated.