SOLUTIONS FOR MODELLING THE ENERGY INPUT IN ELECTRON BEAM MATERIAL PROCESSING

摘要

Additive Layer manufacturing methods constitute an interesting alternative with respect to the production of small series and customized products. Among other advantages, these methods offer an extensive flexibility concerning end customer parts (Rapid Manufacturing) or tools for prototypes and small batches (Rapid Tooling). Up to recent years, machines using laser beams for the solidification of powder material, e.g. Selective Laser Melting, were available on the world market. However, the extensive use of the electron beam in manufacturing processes like welding or perforating revealed its considerable potentials. These are, among others, fast beam deflection, high beam power density as well as high efficiency. Therefore, commercial organizations and research institutions like the iwb make use of this energy source in additive layer manufacturing. The resulting technology Electron Beam Sintering (EBS) is characterized by a complex interaction of various process parameters. In this paper, methods of numerical simulation are used in order to model the process sequence of solidification and to define the governing factors. The heat transfer into the powder bed has been identified as a vital aspect concerning the process stability and the resulting part quality. Therefore, the interaction between beam and powder material is being examined in detail. First, the process is subdivided into discretized solidification steps which enable the definition of a certain system boundary. Second, the determining differential equations are being formed and, due to various boundary conditions, solved using a commercially available software package, implying the Finite Element Method (FEM). Third, the necessary energy input into the powder can be determined and finally, experimental series are being conducted in order to validate the numerical results and identify optimum process parameters.