Scheme for real-time process planning under process deterioration

Abstract

Conventional approaches for process planning of manufacturing operations preset fixed process means and process tolerances for all operations and permit outputs to be distributed around these fixed values, provided that the final outputs meet acceptable specifications. These approaches are inappropriate for high-value and precision manufacturing processes, especially those where a complex part may suffer from process deterioration. The problem is that in these approaches, process means and process tolerances are considered to be independent decision variables, whereby the resultant process means are equal to or close to the design targets of the blueprint dimensions. In addition, they do not consider the phenomena of process shifting or deterioration as factors of manufacturing operations, but assume that process variability is small in comparison to the quality requirements. Therefore, in this study a process optimization model is introduced that simultaneously takes process means and process tolerances into account. Furthermore, it reduces process variability and offsets process deterioration by means of sequential operation adjustment. With the scheme developed in this study built into the control system, a real-time system for integrated process control and modification for making adaptive process planning can be realized.