Warm forming die design, Part III: Design and validation of a warm forming die

Abstract

Warm forming is a sheet metal stamping process at elevated temperature that can significantly expand the forming limits of light weight alloys such as aluminum. Most of the work detailed in the literature has been based on a laboratory setting with minimal guidance on how to design warm forming dies for high-volume production. The challenges that arise when transferring this technology from the laboratory to production are generally focused on the attainment of thermal stability within the die. Thermal stability is required to both maintain the dimensions of the matched die and to provide the sheet with ample formability. Achieving a thermally stable die is a direct function of how the die is heated and insulated. When this is done properly, temperature gradients throughout the die and at the parting surface can be minimized. This work outlines the upfront design approach used for a production-level warm forming die. The die was designed utilizing analytical and thermal finite element analysis tools that were developed specifically to assist with the identification of key design characteristics, such as heater wattages and locations, thermocouple placement, insulation strategy, and overall die architecture. A three-piece warm forming die fitted with resistance heating cartridges was constructed based on the presented design approach. The performance of the die was then validated through simulation and experimental comparisons. The results confirm the performance of the die and validate the predictability of the steady-state temperature response of the parting surface by the thermal finite element software.