Stress and deformation evaluations of scanning strategy effect in selective laser melting

Selective laser melting (SLM) has emerged as one of the primary metal additive manufacturing technologies used for many applications in various industries such as medical and aerospace sectors. However, defects such as part distortion and delamination resulted from process-induced residual stresses are still one of the key challenges that hinder widespread adoptions of SLM. For process parameters, the laser beam scanning path will affect the thermomechanical behaviors of the build part, and thus, altering the scanning pattern may be a possible strategy to reduce residual stresses and deformations through influencing the heat intensity input distributions. In this study, a 3D sequentially coupled finite element (FE) model was developed to investigate the thermomechanical responses in the SLM process. The model was applied to test different scanning strategies and evaluate their effects on part temperature, stress and deformation. The major results are summarized as follows. (1) Among all cases tested, the out-in scanning pattern has the maximum stresses along the X and Y directions; while the 45° inclined line scanning may reduce residual stresses in both directions. (2) Large directional stress differences can be generated by the horizontal line scanning strategy. (3) X and Y directional stress concentrations are shown around the edge of the deposited layers and the interface between the deposited layers and the substrate for all cases. (4) The 45° inclined line scanning case also has a smaller build direction deformation than other cases.