Selection of joining methods in mechanical design

This paper presents a methodology for the selection of joining process in design, implemented in software. The method captures important coupling between the process options, material and design detail, using databases assembled by discussion with experts on mechanical fastening, welding and adhesives. The approach first eliminates solutions that are not technically feasible, with reasons, and then ranks the remaining solutions on the basis of the degree of agreement with the set of design requirements (using a fuzzy logic algorithm). The software implementation presents the designer with a questionnaire, to assemble the set of requirements in terms of the joint geometry, the materials to be joined, the functions required from the joint, and production conditions. Consideration is also given to other 'local' factors that may influence the selection, such as the availability of equipment and necessary skills, or current practice. The application of the methods using the software is illustrated by a case study. The selection tool successfully restricts the number of processes to be evaluated further in a given design, for example, before undertaking the more difficult task of detailed cost evaluation. The method is also successful in suggesting modifications to the design to facilitate joining, or indicating possible innovative use of unfamiliar processes.