Three-dimensional printing system with precision optical path

A three-dimensional printing system for fabricating a three-dimensional article comprising:

• a support plate;
• a resin containment structure supported by the support plate including:
• an upper substructure defining an upper central opening;
• a transparent sheet attached to the upper substructure and closing the upper central opening;
• a lower substructure having a first end and a second end and defining a lower central opening;
• a transparent plate closing the lower central opening;
• and
• a hinge that couples the first end of the lower substructure with the upper substructure;
• an actuator affixed to the support plate and configured for rotatively raising and lowering the second end of the lower substructure with respect to the upper substructure;
• a light engine configured to project radiation up through the transparent plate and the transparent sheet to a build plane above and proximate to the transparent sheet;
• a support tray;
• a movement mechanism coupled to the support tray;
• and
• a controller configured to operate the movement mechanism, the light engine, and the actuator to fabricate the three-dimensional article in a layer-by-layer manner;
• wherein the upper substructure includes:
• a frame that clamps an outer periphery of the transparent sheet;
• and
• a tensioning ring that impinges upon an inner boundary of the transparent sheet.