PREDICTION OF THE DEFORMATION IN STEREOLITHOGRAPHY PRODUCTS BASED ON ELASTIC THERMAL SHRINKAGE

Deformation of some specimens produced by a stereolithography system w as studied experimentally and numerically. Three steps in the rapid pr ototyping process (part building, past removal, and postcure) imposed significant effects on dimensional accuracy. Dimensions of the specime ns were measured after each step. Distortion during part building was much smaller than that caused by the part removal step. The internal r esidual stress developed during the building process was partially rel eased by the removal of the part from the platform. Considerable disto rtion was also observed after postcure. A finite-element computer code was developed to predict the deformation after each step. Shrinkage o f each layer cured by the laser beam was simulated by considering ther mal shrinkage of a solid layer. In order to simulate shrinkage during the postcure process, it was assumed that the postcure occurred from t he exterior surface to the interior surface. Heat sink was also assume d on the boundary of the part for the thermal stress analysis. Numeric al results were consistent with experimental results for the simple ge ometry employed in this study.