Coupled Topology Optimization and Process Simulation System for Laser Powder-bed Fusion Additive Manufacturing

Abstract

Additive Manufacturing (AM), widely known as 3D printing, is a transformative method to industrial manufacturing, helping in creating lighter, stronger, smarter parts and systems. As one of the most important and commercially available AM processes, Laser Powder-bed Fusion (LPBF) can realize geometrically complex metallic parts by selectively melting layers of metallic powders. It is being used extensively in many fields, such as medical, aeronautical, etc.. As AM provides new design opportunities, topology optimization is ideal for AM, specifically LPBF, because it can be deployed to design high-performance structures and fully exploit the fabrication freedom provided by AM. However, there are still some challenges of printing parts in LPBF, such as porosity creation, low surface quality, residual stress, and deformation, which impede its widespread use in industrial applications. These challenges can be controlled by better understanding the influence of the process parameters used in the LPBF process. Nevertheless, relying exclusively on experimental efforts is expensive and time-consuming. Therefore, the LPBF process modeling can help in understanding the effects of the process parameters on the printed part quality. Furthermore, LPBF modeling can be coupled with topology optimization to produce parts with lower as-built deformation. In this work, a coupled topology optimization and process simulation system is proposed to deal with the challenges and utilize the opportunities of the LPBF process. This system involves two major aspects: Firstly, a 3-dimensional heat transfer model is developed to study the effect of process parameters on printed LPBF parts. The simulation results show good agreement with experimental measurements. The averaged error of melt pool width and depth are 2.9% and 7.3%, respectively. Secondly, an Inherent Strain Method (ISM)-based topology optimization model is proposed to reduce the deformation in LPBF parts. A parallel-computing framework of this model is used to optimize the support structures to reduce the as-built and after-cut deflections of printed parts. Experimental results show the framework can reduce the part deformation of over 60% and also material usage of over 50% compared to commercial support structures. Besides, the ISM model has also been employed in predicting the deflections of printed parts, and when compared to experimental results, excellent agreement is observed (average 6% error). Lastly, the parallel-computing framework can achieve considerable simulation acceleration.