Mask Image Planning for Deformation Control in Projection-Based Stereolithography Process

The mask-image-projection-based stereolithography process (MIP-SL) using a digital micromirror device (DMD) is an area-processing-based additive manufacturing (AM) process. In the MIP-SL process, a set of mask images are dynamically projected onto a resin surface to selectively cure liquid resin into layers of an object. Consequently, the MIP-SL process can be faster with a lower cost than the laser-based stereolithography apparatus (SLA) process. Currently an increasing number of companies are developing low-cost 3D printers based on the MIP-SL process. However, current commercially available MIP-SL systems are mostly based on Acrylate resins, which have larger shrinkages when compared to epoxy resins used in the laser-based SLA process. Consequently, controlling the shrinkage-related shape deformation in the MIP-SL process is challenging. In this research, we evaluate different mask image exposing strategies for building part layers and their effects on the deformation control in the MIP-SL process. Accordingly, a mask image planning method and related algorithms have been developed for a given computer-aided design (CAD) model. The planned mask images have been tested by using a commercial MIP-SL machine. The experimental results illustrate that our method can effectively reduce the deformation by as much as 32%. A discussion on the advantages and disadvantages of the mask image planning method and future research directions are also presented.