Process monitoring via quality-oriented SPC under information-based manufacturing

Current SPC charts are process monitoring tools for keeping process in stable status, and cannot assure a desired process quality without additional requirements. To develop a quality-oriented SPC approach, a standardized interface between process quality indices and the parameter design of control charts, i.e., quality-oriented statistical tolerance (QOST), is needed. QOST can be determined based on required process quality index (PQI) or process capability index (PCI). The guidelines of QOST to SPC control charts is actually to determine the permitted deviation of the center lines of SPC charts which is naturally formed by the actual data of process output. Theoretically, when SPC control charts are used to assure the process to be in controlled state and also to meet a predetermined PQI or PCI, it should satisfy the restrict condition representing by a given QOST. The procedures of this new SPC approach with a case study are given for process monitoring under information-based manufacturing.