Abstract

In designing a part to be produced by injection molding or die casting, designers need to consider manufacturing characteristics of the part such as filling and ejectability from the dies as well as functional issues. The typical design cycle is iterative, laborious and time-consuming. In this paper, we present a procedure for defining parting information (locations where the mold/die come together), and recognizing the links between part design and die/mold construction. Many decisions and design details, such as draft on surfaces parallel to the draw (die opening) direction, gate and runner locations, vent locations, etc., depend on the parting locations and characteristics. Parting information is normally not part of the geometric model of the part design. Parting design, including draw direction and parting location, is addressed through a custom user interface which contains several options related to different levels of geometric modeling data. The resulting specification is stored in a segment structure which provides a flexible parting description and fits within the B-rep hierarchy. The reasoning about the linking of related surfaces is accomplished by splitting and traversing the extracted geometric entities based on parting definition. The entities covered by the same die/mold component are aggregated as a face group which is a set of complete or partial surfaces with the parting definition as the boundary information and with the draw direction as the moving information. In this approach, manufacturing information can be strongly coupled with geometric data to form a complete part model which supports manufacturability assessment and facilitates any necessary shape transformations to achieve a manufacturable part in a straightforward manner so that design iterations can be controlled and development cost can be reduced.

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