Selection of manufacturing processes in design and the role of process modelling

The selection of a suitable manufacturing process often involves considerin g the complex coupling between characteristics of the design, the material and the process. Whilst most materials can be well described by a common se t of properties, enabling selection for a given design on the basis of thes e properties alone, the same is only partially true for process selection. The most discriminating characteristics of processes are often specific to the class of process. For example, very different questions arise when sele cting a casting process than when selecting a welding process, so the infor mation needed to answer these questions is mostly specific to each process class. Furthermore, the data and information needed to capture these charac teristics can be strongly influenced by the class of material being process ed there is limited scope for selecting a welding process for aluminium, or steel, or polymers from a generic welding selector that does not have mate rial-specific data. This paper considers the general problem of building se lection tools for specific manufacturing "tasks". A task is defined as a su bset of processes applied to a subset of materials. The goal is to identify systematically the match between the requirements of the design and the ca pabilities of processes. A methodology has been proposed for this task-base d process selection which involves consideration of the attributes of the m aterial, design and process which are relevant to the task in hand. Three l evels of quantitative requirement-attribute coupling are identified for sel ection at the task-level in design. Coupling involving only two or three at tributes can be handled by construction of suitable task-specific process d atabases. More complex interactions require a different approach, in which modelling plays a key role in capturing the relationships between the desig n features, the material behaviour during and after processing, and the pro cess parameters. Modelling is interpreted here in its widest sense: from em pirical rules and curve fits, to advanced statistical methods such as neura l networks, to physically-based process models. The use of modelling opens up great opportunities for making maximum use of sparse process data, for o ptimum co-selection of material and process, and for providing the designer with feedback on the likely influence of processing on the viability and c ost of a design as well as indicating trial processing parameters. This rev iew discusses the general issues with reference to a range of previously st udied selection problems including aluminium casting, joining, welding, and heat treatment of steels. The role of modelling in enhancing selection is illustrated for cutting and welding of carbon steer, and future potential d evelopments are discussed. (C) 2001 Elsevier Science Ltd. All rights reserv ed.