The Research For The Signal Probability And The Strategy Of Q Chart For Small-Batch Production

Nowadays, with the development of the modern economy and industry competition, it is a developing trend to produce by multi-specification and small-batch production. But this brings a challenge to statistical process control, because traditional SPC is used in large batch production. It will cause large economic loss because of no effective quality control methods.Firstly, the paper analyzes the characteristics of small-batch production and some main quality control methods for small-batch production. Then the paper introduces the Q chart suitable for small-batch production and studies its characteristics. In the main chapters, after the situation in which the the parameters are unknown is simulated, signal probability of individual Q chart is studied when subgroup number and shift are various. In this research, MATLAB is utilized to simulate different conditions under which the subgroup number and shift are various and calculate the signal probability. The research result shows that Q chart is not sensitive to the small shift and the signal probability is related to the shift and the subgroup number before the shift occurred. When the shift or the subgroup number before the shift occurred is large,the Q chart has larger signal probability. By the simulating statistical analysis, the paper analizes the signal probability for each of run rule and also discusses the probability of their combination. From the simulating result, it can be seen that the combination of 11-33 and 11-45 has better signal probability. The comparative research on signal probability of the traditional Q chart and the modified Q chart has been furthered, which provides theoretical foundation for choosing suitable chart. On the basis of the research, the application strategy of individual Q chart is proposed. The research could be very meaningful in the production.Finally, the direction of further study and the prospect of Q chart are discussed.