SUMMARY

Mask Projection Stereolithography (MPSLA) is a high resolution manufacturing process that builds parts layer by layer in a photopolymer. In this research, a process planning method to fabricate MPSLA parts with constraints on dimensions, surface finish and build time, is formulated. The “Irradiance model” is formulated which models the irradiance on the resin surface when a given bitmap is imaged onto it. This model is used to formulate the “Inverse Irradiance model”, which generates the bitmap to be imaged onto the resin surface, in order to cure the required layer. Print-through errors occur in multi-layered builds because of radiation penetrating beyond the intended thickness of a layer, causing unwanted curing. In this research, the print through errors are modeled. To this effect, the “Layer cure” model is formulated, that models the thickness of a cured layer as a transient phenomenon, in which, the thickness of the layer being cured increases continuously throughout the duration of exposure. In addition, the effect of diffusion of radicals and oxygen on the cure depth when discrete exposure doses, as opposed to a single continuous exposure dose, are used to cure layers is quantified. The print through model is used to formulate a process planning method to cure multi-layered parts with accurate vertical dimensions. This method is demonstrated by building a test part on the MPSLA system realized as a part of this research. A method to improve the surface finish of down facing surfaces by modulating the exposure supplied at the edges of layers is demonstrated. A case study is demonstrated on a test part with quadratic up- and down-facing surfaces. The part is sliced using a multi-objective slicing routine that achieves the required tradeoff between build time and surface finish of the MPSLA build. The process plan to build the sliced part accurately is generated using the Irradiance model and the Print-through model.