Quality monitoring and adjustment method in manufacturing processes based on integration of SPC and EPC

A quality monitoring and adjustment method based on the integration of SPC and EPC was proposed to solve the problems of quality control caused by noise in manufacturing processes. The integrated model of SPC and EPC based on variation state was built. Under the integrated framework, the methods of exponentially weighted moving average based on Kalman filter and process adjustment based on manufacturing process state were put forward to monitor quality and adjust process variations. Quality offset compensation was achieved while monitoring quality by integrating SPC and EPC. At the stage of quality monitoring, the technology of Kalman filter was first adopted to smooth data and to reduce noise, and then control charts were built by the method of exponentially weighted moving average to monitor processes. Average run length was adopted to verify the performance of the proposed method. At the stage of process adjustment, the model of process adjustment was built for smoothed data, and the variation state estimated values were used to adjust process variation. An application sample was developed to illustrate the feasibility and validity of the proposed quality monitoring and adjustment method.