A novel projection based electro-stereolithography (PES) process for composite printing

Most current additive manufacturing processes can only process one material in one build. Few of them are able to fabricate multiple materials and composites, with limited choices of materials. In this research, we propose a novel Projection based Electro-Stereolithography (PES) process, which is able to fabricate composites with high resolution and fast speed, and a big range of material choices. The proposed novel additive manufacturing process integrates projection-based stereolithography and electrophotography approaches by using a photoconductive film and digital micro-mirror device (DMD). In PES, a photoconductive film is used to collect charged particles in the regions illuminated by light. More specifically, a laser beam is scanning on the film to create a latent image on the film and then a layer of charged particles is attracted to the illuminated area. A liquid bridge system and a stamping system have been developed to transfer particles from the film to liquid resin precisely. Furthermore, a digital mask is used to pattern the light irradiation of the DMD chip to selectively cure the photopolymer liquid resin and particles of that layer. By transferring particles with designed patterns to the resin in a projection based stereolithography system, we will be able to fabricate composites with various materials at microscopic resolutions very quickly. Challenges in this novel manufacturing process, including transferring of particles and curing control, have been discussed and addressed. The corresponding key parameters of the particles collecting, dropping and curing in the PES system have been identified. A proof-of-concept PES testbed has been developed and a couple of tests have been performed to validate the feasibility of the proposed additive manufacturing approach.