The MAST simulation environment

Abstract

MAST is a simulation tool first released commercially in 1980. It includes a data driven model for manufacturing with special algorithms for simulation of detailed material handling activity. Its model of detailed material handling with control algorithms is effective for the design and evaluation of low inventory manufacturing systems such as flexible manufacturing systems. Since that time, the simulation tool has been developed into a problem solving environment. Other tools which have been integrated include a static mathematical model for establishing capacity and feasibility, a detailed model for operator team assignments, a detailed tool requirements model, a queuing theory model for quick results, a graphical interface for both data collection and display of results, finite schedules for each station/operator, and automatic generation of the WIPAC curve.The intention of MAST is to provide an integrated environment of tools from which the user can choose the most appropriate technique for solving a production problem. The static analysis of capacity prevents the simulation of a system which is infeasible. Time is not wasted trying to solve an integration problem when it is really a capacity problem which exists.The queuing theory tool provides a quick estimate for inventory and flow time. These results can be produced in seconds and do not require any layout description. Many times, a concept is evaluated for its impact on reducing the cost of production. And in most cases, cost reduction is achieved by either reduced inventory, reduced labor, or increased productivity. The queuing theory model can provide quick estimate for rough cut comparison between alternatives.The graphical interface is intended to provide the user with specific (tailored) approaches to the class of problem he wants to solve. For example, if his problem is a flow problem such as a conveyor line, then one graphical interface allowing him to start by constructing the layout would be used. On the other hand, if his problem were a flexible production system, then he might choose to start with the process definition. Through a variety of interfaces, the user can select the approach which is most suitable to solving the specific problem.The operator team model has extensive applications toward U-line and other labor limited production systems. This model includes capacity evaluation from team assignments, and provides a finite schedule for each operator as a result of simulation. The direct comparison between planned loadings and simulation results is an effective method for differentiation between labor limited production and machine limited production. Distinguishing this difference is an important step for producing accurate interpretation of a manufacturing system performance.The overall objective of the MAST Environment is to provide state of the art tools which are integrated. Integration is achieved by use of one common set of data, and the ability to directly compare capacity (loading) results, with queuing results, with simulation results. All of this provides a tool which can assist the engineer with solving the complex production problem of the 1990's.This paper is composed of four sections. The first describes the capacity planning model enclosed in MAST, the second describes the queuing theory model, the third is the data driven simulation model, and the fourth is the type of results which can be produced from the various tools.