The basic layer-based manufacturing mechanism of stereolithography is built upon a scanning pattern for the entire cross section for each layer. The purpose of this research is to investigate experimentally and theoretically the effects of a new scanning pattern with the aim of improving the dimensional and geometrical performance of Stereolithography against a benchmarked industry standard scanning pattern. The development of the new Bisector scanning patterns is based on the hypothesis that a contour-oriented scanning sequence with more built-in relaxation could provide a more uniform distribution of residual stress caused by the intrinsic phase transformation due to the photopolymerization process. Experiments on a variety of geometries showed that the new scanning pattern offers substantial improvements in terms of dimensional accuracy, part flatness, surface profile and the system running cost. This further insight into the effects of the scanning patterns was gained through the use of Finite Element (FE) modelling. A commercial FE package ABAQUS was employed to develop thermo-mechanical analogous models to ~nalyse and compare the stresses, strains and distortion induced by each pattern. For the Bisector scanning pattern, the scanning direction and length of scanning vectors are more symmetrical distributed in X and Y axes and hence the distortion or curl occurs in both axes and is comparatively less than that observed for the STAR-WEAVE scanning pattern. If the same overall shrinkage is distributed in both axes then the net distortion must be reduced. The modelling results are consistent with the experimental results of this research, in that the amount of distortion on Bisector scanning patterns is less than the STAR-WEAVE scanning pattern.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:486424 |
| Date | January 2007 |
| Creators | Han, Zhao |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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