QFD based optimal process quality planning

Process quality planning is an important activity of quality assurance. It aims to determine manufacturing processes with appropriate process capability to produce product characteristics. Quality function deployment (QFD) is a powerful tool for quality planning, which starts with identifying customer needs and ends with determining process plans. However, most studies on quality planning by QFD are limited to the product planning stage. The approach to process quality planning through QFD has rarely been discussed. This paper adopts the optimal QFD model and further develops it for process quality planning. By incorporating an empirical capability function for process elements, a composite process capability index (CCp) is presented to reflect the overall process quality level. Constraints including technical feasibility, correlations among process elements, project budget and development time are considered. A case study of the numerical control (NC) machining process quality for a thin-walled complex window frame of airship is given to illustrate how the proposed model can be effectively applied by process quality team to determine the optimal target level of process elements concerning with resources utilization .