Design of an additively-manufactured die for vaporizing foil actuator forming

The flexibility of tooling for individual parts produced by the high-speed Vaporizing Foil Actuator Forming (VFAF) process is increased by replacing the conventional, solid, geometry-bound die with a flexible, low cost, thin, form-giving additively manufactured (AM) polymer die supported by a shear-thickening fluid (STF). During impact of the workpiece onto the AM die, the STF transitions into a quasi-solid state, providing structural support throughout the forming operation. In this study, the design of the air evacuation system is investigated for the production of cranial implants, as a representative example of highly individualized parts. A numerical model is used to determine the necessary pressure required to fully form the sheet and to gain further process insights into the forming process for individual parts. The experiments show that the position and number of air evacuation channels influence the structural integrity of the AM die. Numerical and physical experiments show that the air evacuation channels should be positioned at an angle to the electrical current flow in the side walls to prevent forming of the sheet into the channels and failure of the AM die. This positioning of the air evacuation channels allows successful forming of cranial implants with a nominal geometric deviation of ±1 mm, which is comparable to that reported in the literature for other flexible manufacturing processes. The liquid-solid tooling concept represents a promising alternative to conventional solid steel dies, offering significantly reduced tooling costs, time to manufacture, and enhanced adaptability for individualized production.