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Additive processes, which generate parts in a layered way, have more than 15 years of history. These processes are not exclusively used for prototyping any longer. New opportunities and applications in appropriate manufacturing tasks open up, even though the economical impact is still modest. This review starts with the definition of Rapid Manufacturing and Rapid Tooling, dealing only with direct fabrication methods of components. A systematic material dependent classification of layer manufacturing and process oriented metal part manufacturing techniques are proposed. The generic and the major specific process characteristics and materials are described, mainly for metallic parts, polymer parts and tooling. Examples and applications are cited. The paper attempts to understand the state of the art and the prospective, to put questions, to understand limits, to show opportunities and to draw conclusions based on the state of the art.

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Abstract:A recent study confirmed that the particle size distribution of a metallic powder material has a major influence on the density of a part produced by SLM. Although it is possible to get high density values with different powder types, the processing parameters have to be adjusted accordingly, affecting the process productivity. However, the particle size distribution does not only affect the density but also the surface quality and the mechanical properties of the parts. Therefore, this study compares three different particle size distributions depending on the laser scan velocity and two layer thicknesses of 30μm and 45μm. By using an optimized powder material a low surface roughness can be obtained. A subsequent blasting process can further improve the surface roughness for all powder materials used in this study although this does not change the ranking of the powders with respect to the resulting surface quality.

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