Toward a universal classification and coding system for assemblies

Abstract A variety of group technology-based classification and coding systems have been developed to handle piece parts. These systems typically characterize parts by geometry or processing requirements, or some combination of the two. However, while there are a few situation specific classification and coding systems that address assemblies, there is no universal paradigm for the design and implementation of such a system. Part of the reason for the lack of such a system is probably due to the inherent difficulty in finding a common basis within the diversity of assemblies from industry to industry. This diversity has necessitated a “reinventing of the wheel” from case to case. In this project, we develop a GT-based classification and coding system designed for assemblies, with specific application to a firm in the pulp and paper making machinery industry. At the same time we attempt to develop a general framework for the design of such specialized coding systems. The framework we propose focuses upon GT-based classification and coding systems from the traditional management information system perspective; that is, the needs of the users, current and future, drive the system logic. We perceive two primary uses of the classification and coding systems. One use is for the direct retrieval of engineering designs and manufacturing plans, thus inducing efficiency within the design and planning functions. Thus, the system must reflect the practices. conventions, and culture of the organization. In most cases, this use of the system is the most immediate, it has the most immediate financial benefits, and in our case, it was the rationale for justifying the expense of the project. The second use of such a coding system is to make information contained within the engineering and manufacturing data bases readily available for operational analysis and management decision making. Examples of this include: analysis investigating cellular restructuring, cost and profit analysis of engineering designs, and evolutionary development of engineering standards by judicious editing of the data bases. The first use implies a strong focus on the user, with considerable time spent determining any cultural phenomena which may impact system use. The second use implies a need for extreme clarity in the categorization inherent in the coding structure. For example, considerable time was spent investigating blueprints to determine the diameter frequency distribution of a particular type of forging. Upon consultation with the firm. we discovered that our categorization roughly matched the categorization implicit in the pattern numbers used by their foundry. After a number ot iterations we determined a categorization of the diameter of this particular forging which reflected the reality of the empirical distribution of diameters and adhered closely with the traditionally used pattern numbering scheme. The result was that this portion of the code structure reflected current firm practice while accurately providing frequency of occurrence data which may in the future be useful to management. The dimensions of assemblies considered in our assembly coding system included: Function . The basic functional requirement satisfied by the assembly. Shape . The intrinsic and observable shape of the assembly. Dimensions(s) . Critical dimensional ranges of the assembly. Facets(s) . The inclusion of specific detailed items which support the primary intrinsic function of the assembly. Feature(s) and detail(s) . The inclusion of items which complement the primary intrinsic function of the assembly. Material(s) . The material specification of the assembly. The final form of our coding and retrieval system was three tiered, including a GT-based coding system for piece parts, a custom GT-based coding system for assemblies, integrated with an existing top-down retrieval system for “large” final assemblies (whole paper-making production systems). The top-down retrieval system was based primarily on function, technology, and customer information. The coding and retrieval of final assemblies is used for all components tied to a unique assembly, while the coding and retrieval of piece parts and subassemblies is used for all components that are not specific to any particular final assembly. Such a system allows for rapid coding and retrieval of all piece parts, subassemblies, and assemblies manufactured by the firm.