A three dimensional printing system includes a resin vessel, a light engine, a movement mechanism, a support fixture, and a controller. The resin vessel is for containing a photocurable resin and has a lower portion with a transparent sheet. The light engine is configured to selectively project radiation up through the transparent sheet and over a build plane. The support fixture is coupled to the movement mechanism and has a lower rim that surrounds a central opening and faces the transparent sheet. The controller is configured to: (1) operate the movement mechanism to position the rim at an operating distance from the transparent sheet, (2) operate the light engine and the movement mechanism to form a particle trapping sheet that spans the central opening, and (3) operate the light engine and the movement mechanism to form the three dimensional article.