Stereolithography process enables various freeform geometries to be manufactured, which are beneficial to many research and development fields, particularly on medicine. The mechanical properties of stereolithography models can be generally but not only influenced by the material characteristics, but also by the method of manufacturing. Since the stereolithography process involves building three dimensional objects by depositing material layer-by-layer as well as the post-curing by ultraviolet light, it is therefore possible for stereolithography models to exhibit a directional dependence of the mechanical properties. The objectives of the study focused on the influence of build orientations and ultraviolet post-curing period on the mechanical properties. In the experiments, Watershed 11122 commercial epoxy photo-curable resin was used. The in-house developed stereolithography machine of the National Metal and Materials Technology Center of Thailand was used to fabricate tensile test specimens (American Society for Testing Materials Standard D638) with different build orientations. Main build orientations included flat and edge. Each main build orientation contained three sub-build orientations which were 0 degree, 45 degrees, and 90 degrees to the x-axis. The mechanical properties including elastic modulus, ultimate tensile strength, elongation at ultimate tensile strength, and elongation at break were evaluated by tensile test with a universal testing machine. The results indicated that the mechanical properties of specimens were slightly different among the sub-build orientations. The larger differences of mechanical properties of specimens were found between main build orientations. The mechanical strength of specimens improved corresponding to the increase of UV post-curing period ranged from 0 to 4 hours whereas the post-curing period using 4 hours onward, the mechanical properties of specimens were nearly constant.
