Latest Papers

        The research reported herein first examines the single product-multiple servers case, then a more general, multiple products-multiple servers case is considered.  In both cases, a control strategy is devised and then tested through the use of simulation. The performance of these new control strategies is compared to the performance of the optimal control strategy not considering the timing of any future arrivals (i.e. a Minimum Batch Size strategy). The experimental results indicate that the new control strategies developed perform well under a wide variety of circumstances. 

        In order to demonstrate the multiple products-multiple servers control strategy performance in a realistic setting, a detailed simulation model of the diffusion area of an existing wafer fabrication facility was developed. The model was run with several start rates and the results were compared with similar runs employing a Minimum Batch Size strategy. Results indicate that the new strategy performs well over the wide range of start rates simulated.The new control strategy also has another important advantage over a Minimum Batch Size strategy in that it is parameter free.

The goal of this research is to develop a method for deciding, on a given day, which orders to fill and the assignment of available lots to orders. This decision should be made in order to effectively utilize the capacity of the assembly/test facility, to minimize "wasted" product,i.e.,excess product in partially consumed lots that must be sent to a storage facility, and to maximize on-time delivery of customer orders. 

This problem can be formulated as an integer program with a nonlinear objective and nonlinear constraints. However, it is well known that such integer programs are intractable. Because of the complexity of this formulation we decompose the problem into two linear programs and solve them in sequence by heuristic methods. The two sub problems in this decomposition are the choice of orders to be filled given a capacity constrained factory, followed by filling of these orders by available lots. The solution to the first problem is therefore used as data in the second problem. 

In this paper we describe the problem and it's formulation, focussing primarily on the decomposition into a two stage problem. We then discuss current practice, and propose a simple greedy heuristic. We compare their relative performances using a representative data set. Based on this analysis, we show that our greedy heuristic performs significantly better than current practice. Finally, we give an indication of future research.

This research reexamines the single product-single server case and then explores the multiple products-single server case.For both cases,a control strategy is devised and evaluated through the use of systems simulation.The steady-state performance of each control strategy is then compared to the steady state performance of the theoritical optimal control strategy not considering the timing of future arrivals(i.e.a Minimum Batch Size strategy).The experimental results indicate that the control strategies developed in this paper perform well under most circumstances.

Sponsors included the Production Systems Program of National Science Foundation(NSF),three organizations at Texas A&M University(the department of Industrial Engineering,the Texas Engineering Experiment Station,and the Institute of Manufacturing Systems),and SEMATECH.In addition,Ford Electronics,IBM,and INTEL each sponsored one representative. 

Individuals recognized for their research accomplishments in electronics industry were to participate.Representing ongoing programs across the United States and Mexico in industry,government,and academia,the group identified fertile research directions as a guide for the research community and sponsoring agencies.Intereacting tracks dealt with semiconductor manufacturing and circut card(and higher level)assembly.This paper documents the important research themes identified relative to three topic areas:integrating systems,models for design and operation of production/assembly systems,and assurance sciences.It also summarizes a lively discussion which sought ways to improve the effectiveness of university/industry partnering relationships.This paper includes essential recommndations that resulted from the Workshop,but the interested reader can obtain a somewhat Final Report from Dr.Wilbert E.Wilhelm,the Principal Investigator for the Workshop project.