Quality monitor in multi-operation machining processes based on wavelet filtering

The method of quality monitor based on wavelet filtering was proposed to solve the problems of quality control in multi-operation manufacturing processes, whose measurement data contained noise information. The multi-operation machining process quality control model based on the Stream of Variation (SoV) technology was built, which considered the error propagation. Based on this, the method of discrete wavelet transformation was adopted to smooth data and to reduce noise, and then control charts were built by the method of T-square control chart to monitor processes. The average run length (ARL) was adopted to verify the performance of the proposed quality control method. A sample application was developed to illustrate the feasibility and validity of the proposed quality monitor method.