A double mask projection exposure method for stereolithography

Abstract

Mask Projection Stereolithography (MPSL) is an additive manufacturing technology that allows direct fabrication of complex parts from liquid resin. However, the present MPSL systems cannot meet the requirements of high accuracy and large building envelope at the same time. In order to solve this problem, a Double Mask Projection Stereolithography (DMPSL) system combining two projection modules is proposed based on Digital Micromirror Device. The Large Envelope Projection (LEP) module with a building envelope of 55 mm × 41 mm offers a pixel size of 53.8 μm to achieve large building space. In order to improve the local feature accuracy, the high accuracy features are fabricated by the High Accuracy Projection (HAP) module with a building envelope of 6.8 mm × 5.1 mm, offering a pixel size of 6.6 μm. The calibration and alignment of the system were implemented. The samples for shape and dimension accuracy tests were fabricated by DMPSL, respectively. The results indicated that the shape and dimension accuracy of the features requiring high accuracy was significantly improved. In addition, to overcome the poor mechanical properties at the splicing interface, the effects of splicing shape and overlapping width on the mechanical properties were studied. It was found that the poor mechanical properties can be improved by using straight line splicing strategy with overlapping width of 10 or 20 pixels, which makes DMPSL useful for producing parts that can be directly used in stress environments.