Abstract

Metal Binder Jetting (MBJ) stands out among other Additive Manufacturing (AM) technologies for metals due to its high speed, material flexibility and high volumetric output. It is also an attractive alternative to fusion based AM processes as it does not result in large residual stresses in the part from the build process. In MBJ, a binder is selectively deposited onto the powder bed, bonding these areas together to form a solid part one layer at a time. The printed part from MBJ process, referred to as the green part, is extremely fragile due to low relative density (~50-60%). Therefore, post-processing of MBJ components is essential to achieve the required density in the final part such that it is suitable for service. Sintering is considered the most critical step in the MBJ process-chain to assure acceptable final density and dimensional accuracy in the final component. Sintering often leads to anisotropic shrinkage and distortion in parts which can be detrimental to quality. Therefore, a reliable numerical simulation tool that can accurately predict the warpage and anisotropic shrinkage in the final part considering the essential material and process characteristics is invaluable for the commercial success and industrialisation of MBJ process. In this paper, a finite element (FE) simulation of sintering of an industrial component is presented. Anisotropic initial relative density distribution arising from the build process and anisothermal heat transfer in the oven are considered in the simulation and the final shrinkage and deformation of the part during sintering process is predicted. The predicted shrinkage and deformation are validated with experimental measurements on actual components fabricated using MBJ process. Good agreement is observed between the predicted shrinkage and distortion with that of experimental results. Finally, based on the predicted shrinkage/deformation, a shape-compensation algorithm has been applied to pre-compensate the part such that after sintering the component adheres to the required quality standards.