Gradient light video projection-based stereolithography for continuous production of solid objects

The Video Projection-based Stereolithography (VP-SL) is a fast, low-cost, and high-resolution additive manufacturing (AM) process. However, critical issues, including manufacturing defects such as holes in the solid geometry and manufacturing constraints such as limited size, have been reported. To successfully print a part, the light exposure intensity needs to be carefully controlled. In this paper, a gradient light video projection-based stereolithography (GLVP-SL) process with continuous resin flow is presented. The newly developed AM process enables the continuous fabrication of three-dimensional (3D) solid objects with controlled exposure energy. For each layer, instead of a single image, three mask images are designed with unique grayscale distributions. The effect of grayscale distribution on printing process characteristics including the curing speed and resin flow, is investigated. An optimization model to identify the optimum grayscale distribution pattern for the desired size and density of the solid structure is developed. For comparison, various solid objects were printed with the conventional VP-SL process and our proposed GLVP-SL process. The porosity and surface roughness of the printed parts were characterized. Experimental results validated that the GLVP-SL process can print void-free 3D solid objects with a good surface quality.