טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBendavid Illana
SubjectEconomic Optimization of Off-Line Inspection in a Process
that Produces also Non-Conforming Units when
In-Control and also Conforming Units
when Out-of Control
DepartmentDepartment of Industrial Engineering and Management
Supervisor Professor Yale Herer


Abstract

A finite batch of units is produced by a process subject to random failures. This process starts from the IN state and may shift, while producing a unit, to the OUT state. We consider the case that inspection is conducted after all the units of the batch have been produced and when the production order of the units is preserved. Until now, it was assumed that in the IN state, the process produces only conforming units and in the OUT state, it produces only non-conforming ones. In our research we consider that in the IN state the process may also produce non-conforming units and in the OUT state, it may also produce conforming ones. We develop an optimal inspection/disposition policy that finds which units to inspect and how to dispose of uninspected units in order to minimize the total expected cost, which includes inspection cost and penalty costs due to classification errors. This optimal policy is obtained by formulating the problem and solving it as a dynamic programming problem. Although optimal, this solution is limited since the computational complexity of the dynamic programming algorithm is 0(3n). In addition to the optimal policy we explore four heuristic policies. We conduct an extensive computational study on the optimal policy to check the influence of the model parameters on several aspects of the optimal solution. We then conduct computational studies on the heuristic policies to check their performance relative to the optimal policy and also to compare between the different heuristic policies in cases for which we were not able to compute the optimal policy.