Optimising process planning using groups of precedence between operations based on machined volumes

In this paper we discuss the problem of defining the manufacturing route taken by parts in terms of their technological features. We look closely at the use of the new computer aided process planning (CAPP) systems, and at the need to define groups of operations which will facilitate the generation of the route sheet. Generating different alternatives must be made easier to avoid calculating a range of incoherent possibilities. Our aim was to define groups of precedence between machine operations, which would allow us to reduce the alternatives and therefore, calculate and study the truly plausible routes while ignoring those which, despite being mathematically computable, would not be technologically coherent. In order to determine these groups of precedence, we evaluated a range of parts, which are produced by metal removal using applied group technology. For each one of the parts we generated the possible manufacturing alternatives, and applying graph theory, we determined which operations generally preceded others. The results obtained allowed us to reduce considerably the computational possibilities and thus save time in generating the route sheet.