Research And Application Of Optimal Direction For Raster Scanning Paths In Stereo Lithography Apparatus

Laser is used to sinter the stereo lithography (SLA) parts. The scanning system needs to do plenty of scan, so scan method is very important to SLA process. Efficient scan method can minimize the parts'shrinkage, increase the precision and strength of the SLA parts, improve the fabrication productivity of the SLA machine, and increase of the laser-galvanometer's service life.The character of the scan method currently used in SLA process is investigated in this dissertation. The number of switch-backs at the contour in the path is a major contributor to scanning time. We develop algorithms to pick the direction in which a zigzag path on a polygon will have the minimum number of switch-backs. These algorithms are adopted to generate a new scan method that selects the optimal direction for zigzag path based on section information. This new method can assure the strength of the parts, increase scanning efficiency, shorten fabrication time, increase of the laser service life.For general polygon, it's too complicate to find the optimal direction. But for convex polygon, the problem is reduced. Therefore, two algorithms were proposed to convert an arbitrary polygon into a convex polygon with the same switch-backs.The path generation strategy was studied and the two-dimensional graphics trans-formation theory was used to produce final path data. The optimal direction scanning method was integrated to HRPL series system, which is developed by the Rapid Manufacturing Center of Huazhong University of Science and Technology.The results of the experiment indicate that the fabrication efficiency of SLA parts fabricated with the optimal direction scan method is improved and they have the same strength and precision effect as with other raster scan methods. The method show great effect dealing with polygons with slim characters.