Reducing the Surface Deviation of Streolithographpy Using an Alternative Build Strategy

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Date

1998

Authors

Reeves, P.E
Cobb, R.C..

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Abstract

Considerable research has been undertaken to assess the suitability of different post-process finishing techniques, when used to reduce the surface deviation of Stereolithography components. Such techniques are however limited, as irregular roughness on the SL master often results in a loss in geometric integrity before the desired finish is achieved. Hence, removing much ofthe design intent and traceabilty within the automated fabrication process. Although a number of research initiatives have been undertaken to design layer manufacturing systems which produce inherently smooth surface, the problem of finishing parts from existing. systems remains. The solution currently under investigation by the author is to develop a smooth build cycle within the SL machine, eliminating the need for costly machine modifications. The solution developed by the author uses a strategy, which relies on both part orientation and a fundamental change to the current SLA build cycle. By orientating parts into an optimum build direction, the paper shows how naturally occurring phenomena within the SL process can be used to produce low roughness over a 50-degree window of surfaces. The paper·goes on to demonstrate how, by using a resin meniscus scanned between layers during the·buildiprocess, this smooth envelope can be extended to encompass 90-degree .of surfaces. By scanning fillets between each layer, a reduction in surface roughness of up to 400% can be achieved on some angled planes. The paper concludes that by using this new build algorithm,·the roughness of SL tool cavities can be maintained below 9Jlm Ra on all surfaces. Hence, reducing or even eliminating the need for post-process finishing on all but the most accurate cavities.

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