Geometric mouldability analysis by geometric reasoning and fuzzy decision making
This paper presents a methodology for mouldability analysis by finding the optimal cavity design scheme (CDS) based on manufacturing and cost considerations using part geometry, where a CDS refers to a combination of the parting direction, parting line (PL), and undercut features (UF). The methodology takes advantage of geometric reasoning and fuzzy evaluation, and consists of two main stages: (1) generating all possible design alternatives, and (2) choosing the best alternative. In the first stage, after recognizing the potential UF from the given part, a spherical arrangement is constructed by partitioning the unit direction sphere using outward normals of the part's surfaces with the property that each cell in this arrangement has a unique combination of PL and UF set. Thus all design alternatives can be identified in O(ml2) time by visiting the cells in a certain order and updating the PL and UF set incrementally, where m and l are the number of the part's convex and overall surfaces, respectively. In the second stage, the fuzzy multiple attribute decision-making model is employed to choose the optimal scheme from the set of design alternatives with respect to a set of criteria related to the number and volume of undercuts, flatness of the PL, draw depth, and draft angle. This model allows designers to describe their preferences on different criteria in imprecise linguistic statements. Finally, the case studies show that the proposed methodology is very effective in finding the optimal CDS for the molded part and the final results conform to human designers' experience.
geometric mouldability geometric reasoning fuzzy multiple attribute decision-making design for mouldability mold design