A coordinate SPC model for assuring designated fit quality via quality-oriented statistical tolerancing

On the basis of studies to process quality indices and fit quality indices, the quality-oriented statistical tolerancing is introduced, which provides an interface between fit quality and the process parameter design of mating parts. A statistical mating model via the quality-oriented statistical tolerancing under information-based manufacturing condition is discussed. Compared with traditional mating model for a pair of hole/shaft fit, the statistical mating model is developed for equal batches of hole/shaft fit, and it can achieve a designated fit quality and minimum defective ratio by fully utilizing statistical tolerance zone and the known information of manufactured mating parts via a coordinate SPC model and local network and information system. Thus, production cost for mating parts can be reduced obviously. This new approach provides a possibility and guideline to concurrent design of the process quality, statistical tolerances to assure designated process quality and fit quality for hole and shaft parts.