A CAD/CAM package with filtering capability of digitized surface data for mould cavities

Abstract

This paper describes a PC-based CAD/CAM package for the design and manufacture of mould cavities for producing products with sculptured surfaces. The surface of a product is described by specifying control points on its cross sections. Spline curves are fitted through these control points along both traverse and longitudinal axes. The number of curves fitted depends on the required accuracy. The designed surface can be converted to obtain the shape of a mould cavity by manipulating it with geometric operations such as scaling, left-right inversion and male-female inversion. An utility has also been developed to link the package with a 3-D digitizer to capture the surface geometry of a given pattern effectively. It may be used to filter digitized surface data of the pattern and subsequently convert the data into control points suitable for the package to re-construct or modify the pattern geometry. The package also includes an efficient and easy-to-use cutter path simulation. Triangular facets representing a wire-frame model of the surface can be generated for further analysis, such as shading and calculation of geometrical data of the surface. Cutter paths and hence the control codes for both rough and finish machining the mould cavity on an NC machine can be generated. The cutter paths are automatically planned in accordance with the specified cutter dimensions and allowable tolerance for efficient utilization of the NC machine.