Layer Formations in Electron Beam Sintering

Among direct metal processing manufacturing technologies (Rapid Manufacturing), Electron Beam Sintering (EBS) exhibits a high application potential. Especially, the fast beam deflection provided by electromagnetic lenses allows the realization of considerable building speeds and minor residual stresses. Therefore, this paper aims to examine and utilize the given potential for additive layer manufacturing. In this context, the deployed scanning strategy is a very important aspect. By means of an increasing computer power, innovative and flexible patterns for the solidification of the powder can be implemented. Thus, different patterns are being examined and evaluated. Finally, occurring effects in the exposed zone are introduced. Introduction Due to the trend in direct manufacturing of high-quality metal goods, the importance of the corresponding additive layer manufacturing process is increasing. It is therefore essential, to reliably produce parts with defined requirements like density, stiffness or hardness. This especially includes parts, which are exposed to high strains or must fulfil high demands concerning lightweight construction. Up to now, the additive layer manufacturing of metal parts was dominated by the use of laser beam systems [1]. Despite to the advantages of the additive layer manufacturing technologies [2]. Restrictions exist for the laser based systems regarding the use of different metal materials, the achievable building speed and the porosity of the parts. For example, especially the mirror galvanometers are limiting the process. First, the restricted thermal capacitance of the mirrors is restraining the applicable beam power. Second, a high inertia of the mirrors within the scanning system prevents that the track accuracy is adhered adequately also by a high scanning speed [3]. As a result, the economic use of high-alloyed metals (e.g. tool or stainless steel) is limited. This prohibits a more extensive use of additive layer manufacturing technologies for example in the aerospace industry or the medical technology. It is necessary to solve the described difficulties to establish the additive layer manufacturing technologies for an industrial use. The electron beam as an energy source for the selective melting of powder materials is therefore a promising approach [2, 4]. State of the art The electron beam technology has been established in nearly all metal processing and in a number of other areas. Electron beam generators can possess a power reaching from several Watts up to some hundreds of Kilowatts [5]. They are used for electron-microscopy (low power), for vaporization systems (high power) and for non-thermal processes. Commonly manufacturing technologies, applying an electron beam are assigned to the group joining (e.g. eb-welding),