Research On Process Capability And Control Chart For Mass Varieties And Small Batches Production

Since 1980s, with the sharpening of market competition, market environment in which enterprises existed in has been improved a lot. More and more enterprises realized the importance of competitive on time and satisfaction to customer demands. In the mean time, the focus of competition gradually changed from the price element to some non-price elements such as quality, flexibility and quick delivery. Consequently, the patterns of producing in middle and small batches gained a lot of attention, which is, of course, a great challenge to quality control techniques in the traditional producing process of small varieties and mass batches production.Based on the particularities of mass variety and small batches producing style, and also with the help of knowledge in Management, Probability, and Mathematical Statistics, the thesis will study the quality control techniques and methods in producing process of mass varieties and small batches production from the following respects.①Traditional processes capability evaluation compares the point estimate values and the recommended values of the Processes Capability Indices (PCI), and the accuracy of estimate depends on the sample size. In the environment of mass varieties and small batches production, the point estimates of PCI have large variations if the sample size is small. Therefore, instead of directly judging the grade of process capability, this thesis point estimate the PCI at first and find the confidence limits, then compare the lower confidence limits with recommended values to see if the process can be finished in certain confidence. In this way, it not only improves the curacy of estimate but also declines the risks of judging process capability in the environment of mass varieties and small batches production. To be practical, the confidence limits of some PCI ( C P,C P上,C P下,C Pmand C Pw) in several sample sizes are calculated.Meanwhile, the PCI of small batches production that based on cost control are studied and find that the PCI not only depends on sample size, but also relate to the cost of processing and the losing of substandard products.②Because of small batches and large variations, the probability of"False Alarm"may increase if the traditional control charts are used in mass varieties and small batches production. The thesis discusses the Single Control Chart and Median Control Chart separately, and gives the methods to fix the confidence limits of the two charts. As regards the single control chart in mass varieties and small batches production, the chart...