Study Of The Variables Sampling Inspection Scheme Based On The Process Capability Index

Quality management is an inevitable choice for the survival and development ofenterprises, and we can achieve quality goals and meet users expectation only when theprocess capability meets the requirements. Therefore, how to control process capabilityeffectively has become an important topic in the field of quality control.This paper summarizes the process capability index and sampling theory, and do aresearch about the variables sampling inspection scheme based on the process capabilityindex, the main contents include the following aspects:Firstly, on the basis of summarizing predecessors’ work, this paper introduces thedefinition of process capability and the method for determining process capability. Theevolution of the three generations of process capability index and the relationship betweenprocess capability index and nonconforming proportion are explained systematically. Alsothe significance of process capability index for determining the process capability andproduct quality is explained.Secondly, the concept of sampling is analyzed in-depth, and because the variablessampling inspection can provide much more information than count sampling inspection.So the traditional variables sampling inspections were studied in detail.Finally, according to the principles of traditional variables sampling inspection, twoschemes based on the process capability index were proposed, namely variables samplinginspection scheme for one sample based on the process capability index and variablessampling inspection scheme for resubmitted lots based on the process capability index.We can obtain two inequalities based on the precise distribution function and the nature ofthe OC curve, and find the optimal solution through the dichotomy, then we can developan accurate variables sampling inspection scheme of one sample based on the processcapability index. Meanwhile, to facilitate practical application, this paper shows a tablewhen producer’s risk，consumer’s risk,AQL and LTPD take a certain value, and thetable is made up of the value of the sample size and the threshold. At last, one problem oftinning plant were solved using the variables sampling plan.