Modelling the temperature effects of melt pool position and wall height in additive manufacturing by direct laser deposition

Direct metal deposition by laser is a flexible, single-stage additive manufacturing process that has significant potential impact in rapid prototyping, tooling and small volume manufacturing applications. The process requires either pneumatically conveyed metal powder or wire to be delivered to a melt pool, created by a defocused laser beam. Therefore, the size of the melt pool and the temperature distributions around it are critical in determining process characteristics such as deposition rate. In this paper, the effect that changes in the distance between the deposition head and the melt pool has on these factors, as a part is built-up using a coaxial powder feeding system, is considered via an analytical model. It demonstrates the effect of adjusting the melt pool standoff in different ways on melt pool and powder flow characteristics as a wall grows, and hence allows the effect on build rate to be predicted. Its validity is verified by comparison with a series of 316L stainless steel walls, built using different standoff adjustment methods. The model is found to be able to explain the dimensional characteristics found