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UBC Theses and Dissertations

Die and mould making using the polyhedral concept Lau, Charles Yu-Kit


The ultimate goal of many engineering pursuits is the application of science and mathematics to the production of manufactured products. Manufacturing is the transformation of a designers's ideas into three-dimensional objects with practical application in the real world. Manufacture of products require tools (dies, moulds, punches, etc.) in processes ranging from casting and injection-moulding to forging, punching and coining. These tools, as are all three-dimensional. solids, are bounded by surfaces. Different manufacturing processes present different problems to designers; for example, shrinkage and flash in casting and spring-back in forging or deep drawing. The traditional approach in tool and die-making is based on experienced patternmakers or sculptors making the required object based on engineering blue-prints as well as their own intuition and judgement. With the advent of high speed computers and numerically controlled machines, these traditional procedures can be incorporated into an integrated approach by applying CAD/CAM techniques. The purpose of this research is to develop such general methods for the modelling and making of dies and moulds. Cavity dies consist of bounding surfaces that are either analytical or non-analytical. Analytical shapes are usually designed surfaces which are combinations of surface-elements represented by well known mathematical equations. Non-analytical shapes are often natural surfaces defined by randomly measured data. These require sorting and ordering. In addition, shapes such as ducts, shells and bottles lend themselves to special treatments requiring the input of particular parameters for production of similar items over a long production run. In the work which follows, all of these types of die-cavities have been examined. Examples are given to show how various requirements may be handled by an integrated CAD/CAM approach. Computer routines have been developed in such a way that no special skills in mathematics and programming are required on the part of the user of the programs which can be incorporated into a low cost, fully automated turn-key system.

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