Research On Direct Slicing Method Of CAD Models Under Pro/ENGINEER

Rapid prototyping (RP) technology is a kind of advanced manufacturing technology,which is based on the discreation and deposition of material. And, RP is one of mostimportant direction in the field of the manufacturing. Mask Projection Stereolithography(MPS) is one type of the RP. The principle of the MPS is that3D CAD models are slicedwith slicing software, and section image of3D models can be obtained and saved asimage format. Dynamic masks are produced with the cross-section images whichobtained through the slicing method by dynamic pattern generator. The section view ofpart could be formed on the the photosensitive resin surface. Exposed to laser beam, awhole section of part could be solidified only one-time, then3D real prototyping isfabricated conveniently.Slicing for3D CAD models is one most important step of MPS, and it has directinfluence on the quality of the part surface, production time and the mechanical properties.According to the requirements of MPS, new direct slicing method with Pro/TOOLKIT inPro/ENGINEER environment is developed. There is slice function in Pro/ENGINEER.Therefore, advanced developing application can get the high-accuracy outline of the crosssection on the different position of part, and then, shows the outline in drawing and savesit as image format file through print method.When showing the outline of the section in drawing, Pro/ENGINEER fills the entitypart of section with default profile line. But in the MPS system, this image can not beused directly. Therefore, further treatment is necessary. The paper adopts the callingtemplate method to fill the section. First, it is need to manually design a engineeringdrawing template, which contains information asked by image. These information includeprofile datum, color of parts entity subordinate section, background color, profile name,etc. And then, the template would be invoked by the application when creatingengineering drawing.In the drawing, the image obtained by the way of print can not be applied to MPSsystem, because its wrong white color of background and wrong black color of the section.So, further treatment of the figure is necessary. The course of image processing includesImage Graying and Binary. The method of Gray processing is that make the value of eachpixel’s RGB equal. Through this method,24color image could be transformed into grayscale. Binary processing is that each pixel grayscale value is compared with suitablethreshold Tn selected in advance. The value of pixel point that equal to or greater than thethreshold would be set for255, otherwise, it would be set for0. All the gray value of pixelpoint have been set for0or255. And, the grayscale image shows the obvious effect ofblack and white. Through this way grayscale is transformed into binary image.This paper developed two kinds of slice application, isochoric slicing and adaptiveslicing. According to the specified layer thickness, the first one could process the3DCAD model directly. This method is faster and more convenient and higher precision ofthe parts’ outline than the traditional means known as “STL files”. According to the areadeviation ratio of the cross section, adaptive slicing could automatically adjust thethickness of layer. It increases production time and improves the quality of surface at thegreater rate position. The methods analyzed in this novel provide new solutions for MPSsystem to build objects with high accuracy.