Finite element simulation of selective laser melting based on the layer thickness-dependent shrinkage ratio model

Abstract

During selective laser melting (SLM), a powder undergoes a transition to a molten state and subsequently solidifies. Using a finite element (FE) model to investigate temperature evolution during SLM manufacturing is an efficient and reliable method for parameter and process optimization. However, factors such as the powder layer porosity and material evaporation induced by the laser energy input lead to volume shrinkage of each layer in SLM, which dramatically influences the precision of the FE model. This work investigates the shrinkage in the deposition direction of SLM-fabricated TC4 components with different powder layer thicknesses using a step-shaped substrate. According to the obtained shrinkage ratio, an FE model is used to establish a layer thickness-dependent volume shrinkage ratio. A comparison is made with the commonly used fixed 50% shrinkage ratio model. The study demonstrates that the shrinkage in the deposition direction of components fabricated by SLM using commercial TC4 powder is greatly affected by powder layer thickness. Introducing a layer thickness-dependent shrinkage ratio enhances the precision of the FE model, and it improves the predictive accuracy of the optimized process parameters.