Virtual die spotting: Compensation of elastic behavior of forming presses

The rapid change in the automotive industry towards an electrified and digitalized future necessitates companies to shorten product development cycles. To meet customer needs regarding design and quality, the requirements on the production processes are constantly increasing. As additive manufacturing cannot provide large enough batch sizes yet, conventional stamping of car body parts will be the technology in the foreseeable future. The most time-consuming step during the production of stamping dies is the manual spotting during try-out of the tools. To achieve a homogenous pressure distribution on the parts a precise tool closure is necessary. The behavior of the press has huge influence on the tool closure, especially the elastic deformations of ram, bolster and cushion during forming. Current compensation methods are solely based on experience from previous tools. This contribution presents a methodology for designing a virtual die-compensation to account for press machine behavior based on experimentally determined measurement data of the try-out press. The data is used to calibrate FE-substitute-models of ram and bolster. A forming simulation using rigid tools is coupled with structure simulation using elastic tools and machine. By evaluating the deflection of the active surfaces at the bottom dead center of the press, the necessary die-compensation can be determined.