A METHODOLOGY FOR THE MANUFACTURE OF FORMING TOOLS INCORPORATING COMPLEX SURFACE GEOMETRY WITH MINIMUM COMPUTER RESOURCES

This paper presents a methodology for the manufacture of tools embodying true three-dimensional free-form surfaces using PC-based two-and-a-half axis CADCAM systems. The numerical control machining of free-form surfaces is usually accomplished utilizing minicomputer or main-frame computer aided design and manufacturing (CADCAM) systems. The resulting NC data are suitable for either three axis or five axis machining, dependent upon machine tool type/capability and CAM package complexity. However, the cost of such packages and systems precludes their use in smaller companies with only an occasional requirement for components embodying free-form surfaces. The increasing availability of powerful yet reasonably priced personal computers (PCs) coupled with improving software provides such companies with a far cheaper alternative approach. However, a common feature of PC-based CADCAM systems is that they are limited to two-and-a-half axis machining for all but special applications such as three axis canted Z-plane milling or four axis wire electro discharge machining. All the main functions performed on main-frame systems can be performed on personal computers, such as toolpath generation for free-form surfaces, cusp height determination and change in shape and volume which may be used for component springback compensation.