Abstract
Slurry-based 3D printing allows ceramic green bodies to be fabricated at high packing densities. In contrast to powder-based binder jetting, full densification of printed parts can be achieved in a subsequent sintering step as fine particles dispersed in a suspension are cast and compacted. Slurry-based 3D printing is thus expected to overcome the application limits of the powder-based alternative in metal casting in terms of unfavorable properties like high surface roughness, low density and low mechanical strength. To ensure stress-free drying and therefore high qualities of the compounds made in layers, it is crucial to fabricate single layers with a high level of homogeneity. This paper presents a CFD model based on the open-source simulation environment OpenFOAM to predict the resulting homogeneity of a cast slurry layer with defined parameter sets or coater geometries using the Volume-Of-Fluid method. Moreover, a novel method of spatial reconstruction is proposed to evaluate the surface quality of layers on a minimised computional demand. By comparing the results of the simulation with the real macroscopic behaviour determined in experiments, the approach is found to be a useful tool for suggesting suitable parameters and coater geometries for processing slurries. A precise reconstruction of the outline of the coating area with different process parameters and an approximate prediction of the effect on surface roughness was achieved.
Highlights
Products processed by additive manufacturing (AM) technologies are gaining more and more attention in industrial applications as near net shape components can be produced to a high level of complexity [1, 23]
The 3D printing (3DP) method was developed at the Massachusetts Institute of Technology (MIT) and initially filed as a patent by Sachs et al in 1989 [18]
The application limits of binder-jetted moulds and cores will be extended through the promising technique called “slurry-based 3D Printing” (S-3DP) that is investigated in this study
Summary
Products processed by additive manufacturing (AM) technologies are gaining more and more attention in industrial applications as near net shape components can be produced to a high level of complexity [1, 23]. The 3D printing (3DP) method was developed at the Massachusetts Institute of Technology (MIT) and initially filed as a patent by Sachs et al in 1989 [18] It comprises the repeated process steps of spreading a layer of particle material, applying a binder medium to locally bond the particles in each layer and lowering the building platform. The formation of ceramic layer compounds combines characteristics of tape casting and slip casting [13] It has been studied in different setups and investigated for Selective Laser Sintering [12, 22] or the 3DP method [30]. Jabbari et al [7] evaluated different interface methods when simulating a multiphase flow of non-Newtonian ceramic slurries in tape casting. The objective of this paper is to propose a CFD approach to simulate the slurry deposition process, to suggest appropriate process parameters and advanced coater geometries for homogeneous layers, and to create the basis for faster process developments in S-3DP
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