Rapid prototyping of sheet metal components by plasma-jet forming

Conventional precision forming of sheet metal components requires the use of mechanical tools. However, during product development, different tools may be required to form various shapes, thus necessitating significant tool cost and lead time. If a rapid prototyping process were available such that the required shapes can be formed without the need for hard tools, the potential reduction in product development cost and lead time could be quite significant. Moreover, such a process could be used for very short run production where it would be uneconomical to amortize tooling cost over a small number of manufactured pieces. To explore the potential for flexible forming without tools, various researchers have used a laser beam as a heat source to induce deformation in sheet metals by means of thermal stresses. Some success has been demonstrated with such an approach. However, laser systems have several disadvantages, which can be circumvented by the use of a plasma-jet as a heat source. This paper describes the use of a robotic system to manipulate a non-transferred arc plasma torch as a controllable heat source to generate internal stress in sheet metals, thus causing plastic deformation without the necessity of hard tooling. Simple linear bends have been produced in several sheet materials of 0.8mm thickness to evaluate the effect of various process and material parameters. Some evaluation of material properties resulting from the bending operation has been conducted. The key process parameters affecting the rate of bending have been identified as those governing the amount and rate of heat input to the sheet surface, and the temperature gradient developed between the front and back sheet surfaces. It has been demonstrated that the principal sheet metal physical property affecting bending behavior is the thermal conductivity. Results are presented to illustrate these various effects.