A system-level model of variation propagation in a sheet stretch forming manufacturing system is developed and explored. The system model is composed of sub-models of heat treatment, including quenching and natural aging, and stretch forming. Both the nominal and variation predictions of the model are compared to measured production data. Factors in the system which are most sensitive to variation are identified, and a variation reduction strategy is discussed. This strategy lead to a 30% reduction in part strain variation on the factory floor.