Quality-oriented Statistical Tolerancing and its Application in Process Quality Monitoring

The process quality index (PQI) system and quality-oriented statistical tolerancing have been discussed based on three PQIs, which provides a standardized interface between process quality requirements and control chart design. An integrated statistical approach to specification, production, process monitoring and inspection can be realized via using quality-oriented statistical tolerancing. By adding a restriction to the center lines of and R chart or and s chart based on the PQI-oriented statistical tolerance zone, a new SPC approach for assuring both predetermined quality and process stability is presented, which enhance the function of control charts and provides a possibility and guideline to concurrent design for the process quality plan, statistical tolerance and related parameters of SPC to assure designated process quality.