Production of individual sheet parts using vaporizing foil actuator forming and a flexible liquid-solid tool

Abstract

Conventional sheet metal forming is inflexible, as each part requires costly punch-and-die tools, usually produced by machining of solid steel. These tools are suitable for large batches but inefficient for individual parts, as the cost per part is high. The aim is to produce individual parts with flexibly applicable tools to also reduce the tool costs per part. The high-speed process of vaporizing foil actuator forming (VFAF) decreases the tool costs by replacing the solid steel punch with a flexible, low-cost, electrically exploding aluminum foil. Until now, also VFAF relies on conventional solid steel dies. This paper investigates the feasibility of a novel flexible liquid-solid tool to manufacture patient-specific cranial implants as an example of highly individual parts. The liquid solid-tool comprises of a thin form-giving additively manufactured (AM) polymer die which is supported by a shear thickening fluid (STF). When the sheet impacts the AM polymer, the STF behaves quasi-solid providing structural die support during forming. The new tool concept also increases the flexibility by potentially reusing a part of the tool – the STF. The results show that the new tool can be designed to successfully manufacture cranial implants with a nominal geometry deviation of ± 1 mm. The deviation lies in the range of other competing flexible processes like powder bed fusion or single point incremental forming. Hence, the liquid-solid tool can replace solid steel dies and decrease the tool costs drastically compared to the solid dies.