The Study On Optimal Allocation And Policy Of On-Line And Off-Line Quality Inspection Within A Manufacturing Line

Nowadays,in global intense market competition,the model of the market competition is turning from price competition into quality competition.The production-oriented enterprises are facing one of the most important challenges: how to improve the quality of products to ensure the core competitiveness.It is a great challenge for managers to make decisions on allocation of inspection stations to pursuit high quality and cost effectiveness.This dissertation deals with the optimal allocation and policy of on-line and off-line quality inspection within a manufacturing line.The research works of this dissertation includes the following four parts:First,a model of optimal locations of on-line inspection stations is proposed which takes the minimum cost of qualified products as the goal.The model takes transfer cost of defective units and interaction of workstations within a serial manufacturing line into consideration.This model enables to get the optimal number and postions of on-line inspection stations.A calculation method for the rolled throughput yield is obatained based on this proposed model.An algorithm to the model is also presented.Involving the factor of inspection errors,an optimal location of on-line inspection stations aiming at the minimization of the expected total cost is established.Similarly,the calculation method for the rolled throughput yield is given.Second,based on the general model of off-line quality inspection policy,the manufacturing variation within a manufacturing line is considered.In the absence of inspection time,three modes of prior information are proposed and nine no-inspection policies are given.By introducing the parameter ? to represent the confidence level in the identification of a unit if it is in the in-control state,an off-line quality inspection policy based on the three modes of prior information is proposed with minimizing the expected total cost.It is also demonstrated that,the remaing units can be renumbered from 1 according to priority after the implement of the off-line inspection policy.The stopping rules and inspection procedure for this policy are given,too.Under the condition that the inspection time is non-negligible,the calculation method for expected inspection number and expeted insepection cost are obtained.Third,based on the model of on-line inspection and the no-inspection policy in the off-line inspection policy,integrated policies of on-line and off-line quality inspection from three aspects are proposed with the goal of minimal expected total cost.(1)If there is one inspection station in every workstation,the optimal number of units which are conducted on-line inspection is derived.The calculation method for the rolled throughput yield is given.(2)Regard the integrated on-line and off-line inspection policies as a whole to be an inspection station,a model for the optimal number and positions of the inspection statations within a manufacturing line is established.Besides,the optimal number of units conducted on-line inspection is given.A calculation method for the rolled throughput yield is obatained.(3)When manufacturing variation is considered,the number of units conducted on-line inspection in every workstation is obtained.Fourth,taking the serial-parallel manufacturing line as the research object and minimizing the total cost as objective function,a model of optimal allocation of on-line inspection stations is proposed,thus the optimal number and positions are obtained.In order to restrain defective units from exiting the serial-parallel manufacturing line,a model of operating modes for defective units(rework or scrap)is established when on-line inspection stations are located in every worksations.In addition,with consideration of the model of on-line inspection station allocation and the model of operating modes for defective units,an integrated policy is established.Finally,a case study of a certain kind of electronic component shell from an electronic technology company,which is part of a research institute of China Electronics Technology Group Corporation,is provided.A research on engineering application of the proposed models of optimal allocation and policy of on-line and off-line quality inspection is given,in order to provide the most suitable quality inspection policy for this company.This dissertation has important significance in theoretical and practical in quality inspection field.The research works are based on the features and problems of the quality inspection in real application,new models of quality inspection allocation and policy are established.The consequences of this dissertation enrich the research on quality inspection and can be used to assist business managers in making production decisions.