Image processing-based accessibility analysis method for determining undercut-free parting direction
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In injection molding, demoldability of a part without the use of a side core is possible only if all of its surfaces are fully accessible in the parting direction. A mold surface may be fully accessible from some directions, but may not be accessible from other directions. Therefore, to determine the undercut-free parting direction, an algorithm is developed that evaluates the accessibility of each part surface from a set of directions (called as candidate parting directions) by using image processing techniques. In the proposed methodology, the surface accessibility is determined by comparing the projected area of each surface on the image plane in the presence of other part surfaces to that of the same surface in the absence of other part surfaces. The algorithm can be used to determine the accessibility of planar, ruled, and free-form surfaces without tessellating the part surfaces. The algorithm includes a method that can also successfully classify surfaces that are oriented perpendicular to the parting direction. The surface classification can be used to identify the undercut-free parting direction, recognize the various undercut features, and form the visibility maps. The accuracy of the algorithm depends upon the number of pixels used to represent the part on the computer screen. The method has been successfully implemented, and test results are discussed in this paper.
KeywordsAccessibility analysis Image processing Demoldability Mold undercuts
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