Practical Issues in the Application of Direct Metal Laser Sintering

Direct Metal Laser Sintering (DMLS) was introduced to meet the objective of producing metal parts directly from CAD data. CRDM has accumulated six years of experience in applying this technique, mostly to prototyping parts for evaluation. For some applications, such as blow moulds, porosity generated in DMLS has proved to be beneficial, but for others a concession on tolerances or finish are necessary and/or complementary operations are required, which add to manufacturing time and cost. This paper examines such issues through some well chosen examples of parts to demonstrate both the strengths and weaknesses of the DMLS process. Introduction The development of the Direct Metal Layer Sintering technique for producing metal parts with complex geometry directly from CAD data has raised expectations for considerable financial savings and greatly reducing manufacturing times. There are two essential variants of DMLS, powder bed and powder deposition. In the powder deposition approach, an alloy is melted and deposited layer-by-layer. While the powder deposition route is more amenable to functional grading through the addition of multiple materials to the build, deposition rates tend to be somewhat slow. In powder bed technologies, a laser or another heat source melts, sinters or bonds a layer of powdered metal; see Fig. 1. This approach has the advantages of fast build rates and the ability, within limits, for builds to be self supporting, but it tends to restrict the composition to a single alloy. Figure 1: Basic features of the powder bed DMLS process.