Optimum Target Value for Two Processes in Series: Case of Hybrid Tubular Expansion

摘要

In this paper, a manufacturing system with two machines in series was investigated. The optimum process mean and screening limits of a surrogate variable through two machines in series with 100% inspection are investigated. In this procedure, the variable is inspected first to decide whether to be accepted or rejected. After accepting the product from the first machine, it goes to the second machine which has three classifications, accept, or reject and rework on the second machine or reject then rework for both machines. Assuming that the performance of variables are jointed normally distributed, the optimum process mean are obtained by maximizing the expected profit or minimizing the production cost which includes selling price, production, reprocessing, inspection and penalty costs. This method is applied to joining tube-tubesheet expansion process in heat exchangers using hybrid method which includes hydraulic then rolling processes. The target dimension chosen is the wall reduction percentage of the tube thickness. A numerical example is presented.