The Development of Plasma Transferred Arc Solid Free Form Fabrication as a Cost Effective Production Methodology

摘要

Rapid prototyping, also known as solid free from fabrication or SFFF, has been extensively demonstrated as a process to produce limited numbers of prototype components. The majority of that work has been carried out using lasers as the energy source. Laser SFFF processing has significant limitations owing to the limited energy levels available, energy absorptivity, electrical and process inefficiencies, and capital cost. In addition, the complex optics of the laser alignment system present serious difficulties in maintaining that alignment in anything other than a laboratory type environment. MER has addressed those difficulties by using a high-energy plasma transferred arc (PTA) for the energy source. MER has built a state of the art PTA SFFF system. The capital and operating costs for the PTA SFFF are a fraction of that for the laser systems. In addition, operating efficiencies are much higher for the PTA system. The powder, gas feed and plasma arc of the PTA SFFF are all coaxial, eliminating any alignment issues. The MER unit is capable of producing components up to 2' by 2' by 17' in size, and employs four powder feeders for the fabrication of complex composite structures. The unit has a large torch for maximum deposition rates, and a micro torch for fine features. Properties of materials fabricated by MER using this process are discussed in this paper.