Three-dimensional numerical approach for geometrical prediction of multilayer laser solid freeform fabrication process

This article presents the development of a three-dimensional numerical method for predicting transient geometrical and thermal characteristics of multilayer laser solid freeform fabrication as a function of process parameters and material properties. In the proposed method, the thermal domain is numerically obtained, assuming the interaction between the laser beam and powder stream is to be decoupled. Once the melt pool boundary is obtained, the physical domain is discretized in a cross-sectional direction. Based on the powder feed rate, elapsed time, and intersection of the melt pool and powder stream area substrate, layers of additive material are then added onto the nonplanar domain. A standard object is fit to each added layer to facilitate the numerical analysis of successive layers. Variations in physical parameters due to formation of nonplanar surfaces are incorporated into the model to increase the accuracy and reliability of the simulated results. The developed model was used to predict the geometrical and thermal properties of a four-layer thin wall of AISI 4340 steel. The results show that the temperature and the thickness of the deposited layers sensibly increase at the end point of layers 2, 3, and 4. Also, the powder catchment efficiency for the first layer is significantly lower than those of successive layers. The experimental results demonstrate the validity of the developed numerical methodology.