A closed-loop process analysis and control system for machining parts

In the production of parts involving multiple interrelated machining operations a process plan is developed and then checked for feasibility using the tolerance charting technique. Owing to inherent variations in manufacturing processes a feasible process plan does not guarantee an acceptable product. Because of the discrete nature of the machining operations and the interrelationship between different dimensions, information on a produced dimension may be used to control the subsequent operations and thus ensure that a part meets specifications. A closed-loop process analysis and control system (PACS) has been developed for this purpose. The closed-loop PACS has several components. The core of the closed-loop PACS is the process adjustment routine (PAR). In the implementation of PAR the actual dimensional information is gathered online and is fed back to PAR, which then advises the machine operator to make adjustments to subsequent operations so that the part is produced with a higher degree of quality. This paper provides an overview of the closed-loop PACS and presents the techniques and procedures for the development and implementation of PAR.