Using mechanical hardware to simplify process planning

摘要

Process planning is an important and complex task in manufacturing. In this paper we present theview that process planning is difficult to automate because of the state of machining technology today.Many standard practices in machining, like fixturing, are really specific solutions that have evolvedover the years for particular problems; modeling this patchwork of technologies, and planning withthem is inherently difficult. To show this, we attempt to cast process planning for machining in theform of traditional Al planning problem using predicate calculus. Specifically, we identify a class ofinteractions, known as global interactions, that make the resulting planning task very difficult. Weshow how many of these global interactions can be approximated as pairwise ordering constraintsthat are amenable to well known nonlinear planning techniques. However some global interactions,particularly those arising from fixturing and rigidity concerns, do not lend themselves to suchsimplification. To handle these interactions we propose that a paradigm-shift is required in machiningtechnology. We describe a new fixturing technology called reference free part encapsulation (RFPE)that makes it possible to manufacture almost arbitrarily complex components. RFPE makes itpossible to ignore global interactions and therefore justifies the reduction of general process planningto a nonlinear planning problem.