Quality Improvement Model Considering Rework and Imperfect Inspection

Abstract

Quality improvement can be achieved by improving several important aspects in the production process including the inspection process. The inspection process is often considered as a trivial problem for some companies. Most companies perform inspection process in the final stages of the production. This means that the defective product has been manufactured at the time they are inspected. This causes the company should bare additional costs for reworking the defective products. To reduce the costs incurred for reworking defective products, quality improvement must be performed in the process.

Another problem that is important regarding inspection is the presence of imperfect inspection. An inspector may make mistakes in the inspection process, either it categorizing a good product as defective or a defective product as a good one. Problems related to the imperfect inspection will be detrimental to both parties, both from the company and the customers. This paper aims to develop an optimization model for quality improvement by considering the rework process and imperfect inspection. The optimization process is done based on trading off the components of the model to determine the optimal tolerance value and also the optimal investment that must be paid by the company. Optimization is not only done to obtain optimal tolerance values but also other aspects such as economic investment value, manufacturing costs, customer loss and costs due to imperfect inspection process. Two different policies will be presented to determine the impact of optimal tolerance. Numerical example is given to show the application of the proposed model.