Fabrication of smooth surfaces based on mask projection stereolithography

The surface finish is critical for applications such as micro-fluid mixing and self-assembly that requires smooth fluidic flow and mechanical rotation respectively. However, in layer-based additive manufacturing processes, it is well known that the stair-stepping effect exists in the fabricated surfaces since a three-dimensional model is approximated by a set of two-dimensional layers. The fabricated surfaces are especially poor for the ones that are close to the horizontal plane. In this paper a novel approach for achieving improved surface finish has been presented for the mask-image-projection-based Stereolithography (MIP-SL) process. Theoretical models and parameter characterization are presented with experimental verification. The developed approaches have been incorporated in the process planning of the MIP-SL process. Multiple test cases based on various types of curved surfaces have been performed. A comparison of the built results based on the traditional and the newly developed approaches has been discussed to illustrate the effectiveness of our method.