Slicing of 3D CAD models for mould design

by Wong, Teng

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled Slicing of 3D CAD models for mould design submitted by Wong Teng for the degree of Master of Philosophy at the University of Hong Kong in August 1998 Plastic Injection Moulding plays an important role in modern manufacturing industry. Traditionally, the parting line and parting surface formation rely heavily on experienced mould designers/makers. The use of Computer-Aided Design (CAD) software enhances the overall design process and decreases the design lead time. Past algorithms on computer-aided parting line and parting surface formation have been reported. However, most of them deal with product models with planar or simple curved surfaces. Little examples on parting line formation of free-form product models are illustrated. The applicability of these algorithms to free-form product models are questionable. A new algorithm on parting line and parting surface formation is suggested. The proposed algorithm uses uneven slicing method to locate the required parting line of a product model. The parting line location relies on the intersection profiles of the product model with each slicing plane and is independent of the natures of the surfaces constituting the product model. Therefore, the parting line of free-form product model can be determined easily with the new algorithm. A product model can have either a single closed outer parting line or a single closed outer parting line and several closed inner parting lines along a parting direction. The new algorithm is able to locate all i the outer and inner parting lines along the selected parting directions. The presence of undercuts affects the layout of the parting surfaces and the mouldability of product models. The new undercut detection algorithm consists of two tests. Grid Line Test, the first test of the undercut detection algorithm, capitalizes the intersection profiles obtained from the slicing operation to quickly screen out the suspected undercut surfaces. The second test, Column Intersection Test, distinguishes the actual undercut surfaces from those suspected undercut surfaces. With these tests, the mouldability of the product model along a specified parting direction can be determined. Besides the parting line formation and undercut detection algorithms, the formation of the entire mould block is also established. The mould block formation caters for the feeding system formation, cooling system formation, ejecting system formation and the formation of multi-cavity mould. These provide a clear layout on the overall mould block which can serve as a preliminary reference for mould designers. Several application examples are illustrated in this thesis. The time response is very good. The proposed algorithms help mould designers to design the mould layout in a more systematic manner right at the outset. 11
Bibliographical Information:


School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:injection molding of plastics data processing


Date of Publication:01/01/1998

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