USING MECHANICAL HARDWARE TO SIMPLIFY PROCESS PLANNING

Process planning is an important and complex task in manufacturing. In this paper we present the view that process planning is difficult to automate because of the state of machining technology today. Many stan dard practices in machining, like fixturing, are really specific solut ions that have evolved over the years for particular problems; modelin g this patchwork of technologies, and planning with them is inherently difficult. To show this, we attempt to cast process planning for mach ining in the form of traditional Al planning problem using predicate c alculus. Specifically, we identify a class of interactions, known as g lobal interactions, that make the resulting planning task very difficu lt. We show how many of these global interactions can be approximated as pairwise ordering constraints that are amenable to well known nonli near planning techniques. However, some global interactions, particula rly those arising from fixturing and rigidity concerns, do not lend th emselves to such simplification. To handle these interactions we propo se that a paradigm-shift is required in machining technology. We descr ibe a new fixturing technology called reference free part encapsulatio n (RFPE) that makes it posssible to manufacture almost arbitrarily com plex components. RFPE makes it possible to ignore global interactions and therefore justifies the reduction of general process planning to a nonlinear planning problem. (C) 1998 Elsevier Science Ltd. All rights reserved.