Inspection plans for multi-component multi-stage production system

Abstract

This thesis is concerned with the design of inspection plans for a production system where a product is manufactured in a series of distinct processing stations and consists of identical components to be inspected by more than one method. This thesis is divided into the following three parts. (i) An economic design of inspection effort allocation is considered for a serial production system in which a product consists of many identical components, only a limited number of automatic inspection machines is available, and the rate of production is constrained by the rate of inspection. A cost model is constructed and a method of finding optimal locations of inspection machines and inspection level - proportion of components inspected - is presented. For situations where the numbers of stages and inspection machines are large, a heuristic allocation algorithm using dynamic programming is proposed. A numerical example describing the solution procedure and a simulation study evaluating performance of the proposed heuristic algorithm are given. (ii) An economic design of inspection effort allocation is considered for a production system with a processing station and a multi-step inspection station in which several types of defects in a product can be detected by different inspection methods. For situations where the rate of production is constrained by the rate of inspection and a product has many identical components, two alternatives for inspection effort allocation - inspecting all components in a sampled unit and inspecting a portion of components in all units - are considered. A cost model is constructed and a method of finding optimal inspection levels at each step is presented. Numerical examples describing the solution procedure are given and performances of the two alternatives are compared in terms of expected total cost per unit. (iii) An economic design of rectifying inspection plans is considered for a product with several types of defects which can be...