A phenomenological finite element model of part building in the stereolithography process

Abstract

The finite element method has been used to develop the framework for a tool that can be used to model the structural deformation arising from the stereolithography build process. Such a tool when fully developed can facilitate numerical studies aimed at evaluating build parameters and build styles. Although the current software makes no attempt to capture all the physics of the process, provisions for three important build features have been made: (1) laser path history including scanning rate and depth of cure, (2) structural linkage, and (3) time varying material behavior. For demonstration purposes, a three dimensional finite element code was modified to include a phenomenological material model of solidification. The model was based on cure shrinkage and stress relaxation data collected from in-situ tests on individual strands drawn using 3D Systems` stereolithography apparatus (SLA-250). To depict the directed path of solidification within layers, a finite element birthing scheme was conceived to activate elements along the predetermined coordinate path of the laser. Structural linkage was enforced by joining element strands of layers when laser paths connect or overlap, respectively. A limited number of analyses have been performed to contrast simple build styles

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