Variation reduction strateties have traditionally focused on treating the output of a single manufacturing operation. In practice, however, manufacturing systems are comprised of multiple operations, each of which can add to or reduce product variation. Additionally, the sensitivity of each operation to input variation is a function of the operating point, which can only be changed in conjunction with the operating points of all other operations in that system. As such, optimizing each operation within a system individually does not guarantee lowest end-of-line variation. What is needed instead is a method for conducting a system-level parameter design in which the operating points of each operation are optimized as a complete set to reduce final product variation. The logistics of such an integrated parameter design scheme make changes or designed experiments on the actual system unwieldy or impossible: instead a system level model can be used. In this paper we use Integrated System Models to conduct system-level parameter design. We demonstrate this technique on a model of a sheet stretch-forming manufacturing system. Through this example, we show that selecting operating points while considering the entire system results in a greater reduction in variation than Taguchi-style robust design conducted independently on each of the operations within the system.
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