SOME ISSUES ON INPUT CONTROL, BUFFERING AND PROCUREMENT IN ADVANCED MANUFACTURING SYSTEMS

Abstract

With managing environmental uncertainty in advanced manufacturing systems as the underlying theme and economic functions like cost and profit as objectives, this thesis analyses three problems, one each in the areas of input control, buffering and buyer-supplier relationships. In the input control problem in a Flexible Manufacturing System (FMS), we have derived conditions that support the mixing of a part-type which can share the setup of other part-types, for both the dedicated and the random FMS. The deterministic problem, which is the dedicated FMS, is identified to be a special Economic Lot Scheduling Problem (ELSP), and is formulated as a linear programming problem. The stochastic problem, which is the random FMS, is modeled as a polling system. In view of the complex nature of the model and the accompanying results, numerical treatment is resorted to for a three-part problem. Results are also supported with charts. In this chapter, a noteworthy finding is that, in the case of uncertain demand, if decision to mix this particular part-type is taken then it is best to mix it with that family for which the traffic intensity is the highest. The second problem taken up inquires into possible dynamic and uncertain environments that might support the use of a constant overplanning factor as the buffering strategy as used by Toyota. First, a general capacitated model is analysed. As the investigation is about Toyota's overplanning factor, we consider an uncapacitated model. The analysis leads to an interesting find that for most of the probability distributions (except the exponential distribution) which are used to model uncertain and non-stationary demand environments, the overplanning factor is a constant as long as the coefficient of variation of the forecast error distributions remains constant. Notwithstanding this 'over-simplification', Toyota's success in JIT production is legendary. We also look qualitatively into what makes Toyota tick. The last problem studied is concerned with the benefits of transparent relationships between manufacturers and suppliers. Though there are studies in the literature on co-ordinated inventory systems, not many are concerned about the strategies to be adopted benefit, when the buyer comes up with the counter strategy of order splitting, is derived. A detailed numerical analysis is done together with charts to illustrate the cases. Finally, the thesis concludes with the consolidation of the results obtained together with their limitations.