Modeling layer geometry in directed energy deposition with laser for additive manufacturing

Abstract

Additive manufacturing applications in the aeronautic, automotive, and biomedical industries have increased significantly in recent years as a result of design flexibility. In this regard, several methods are available, notably Directed Energy Deposition with laser (DED-L). However, to achieve the optimum parameters for each situation, a high number of experiments is necessary. Numerical simulations are useful in this context, as they are able to predict trends without conducting exhaustive tests. Mathematical models based on geometrical functions, also known as multi-layer multi-bead (MLMB) models, have been recently introduced in this field and they present good results for the surface profile. Also, their implementation is relatively simple. The aim of this study was to develop and validate a model that can provide a good approximation of the geometrical profile of DED beads. The existing models for DED have not been validated for different materials or applied to different build-up strategies, such as alternated overlapping beads. Thus, a new system of equations had to be implemented for the alternate overlapping build-up strategy. When an existing model was used for iron and Inconel 625, it was noted that the bead width and area were not kept constant during the deposition. The powder catchment efficiency was estimated for both materials and in fact, changed depending on bead position. Therefore, the adjustment was required and a correction factor was applied. In addition, for Inconel, the type of function used for the individual beads was not the same as that for the central beads, which also contradicts the initial assumptions. After applying the new assumptions, errors of 4% for the iron deposits and 10% for the Inconel deposits were obtained. This demonstrates that the proposed mathematical model can be used for the prediction of the deposited layer in additive manufacturing.