Research On The Evaluation Of Process-capability Index In Series-Operation

In the series-operation industry such as metallurgical industry, the quality operators can often meet such questions as follows: sometimes, the process-capability index in one or several operations is very bad, but the eventual quality of the products is very good. That is because in series-operation, the quality of the products in the lower operation depends on the quality of the operation and the quality of the higher operation as well. On the contrary , the lower operation is not only influenced by the higher operation, but also can control or improve some of the qualities in the higher operation. And so it can eventually satisfy the final quality demand. In the lower operation re-controlled series-operation can the operation-ability index in the higher operation be relaxed? This essay explained the correlations between the series-operations, re-defined the process-capability index which improved the traditional process-capability index based on independent operations. According to the correlations between the lower and higher series the demands of the lower operation, This essay draw a conclusion about "the exact process-capability index", so that it can be used to see whether the process-capability in the higher operation will meet the demand. In order to avoid chasing the too high quality and this can save the cost of the production. Furthermore, according to the cost-profit, This essay worked out the exact process-capability index in the higher operation from the eventual product quality demand. Compare the total cost of the lower and higher series based on this standard with that before the adjust, we can work out the process-capability index in all the series which can satisfy the eventual quality demand and the demand of the lowest cost of the product. This can no only serve the best economic production, but also aid the modern enterprise shift from push-manner to pull-manner.