Design and Fabrication of Large Area Vat Photopolymerization 3D Printing System using a 32-inch Quasi-Collimated Visible Backlight Module with Local Dimming Control

In this paper, we accomplished the first 32-inch liquid crystal display (LCD) type vat photopolymerization 3D printing system based on the quasi-collimated visible backlight module with local dimming control. The large building area (40 × 70cm) of the 3D printing system can greatly increase the size of printing objects and the production rate. We focused on the design of quasi-collimated backlights and analyzed their optical properties and the appearance of 3D printing objects fabricated by them. The optical performances of the quasi-collimated backlight using stacks of optical films feature no large angle leakage light, 86 % intensity uniformity, and less than ±15° angular distribution of emitting light. After the optimization process by combining a variety of optical films, the uniformity, and collimation of the backlight module are greatly improved. Moreover, combining a local dimming algorithm with 3D printing technology can completely suppress unexpected photopolymerization residues, increase resin utilization rate, save energy, and greatly improve the probability of success in the 3D printing process, especially in large printing objects.