AN IMAGE DETECTION APPROACH TO NC ROUGH-CUT MILLING FROM SOLID MODELS

This paper presents a method of converting information from a CAD soli d model into a form suitable for CAM operation. The rough machining of a cavity into a block is used to illustrate the working of the system . This example was chosen because the machining of cavities presents d ifficulties as outlined below and rough machining involves the removal of more material than finish machining and therefore is of more econo mic significance in a production process. A three-axis NC miller is us ed to cut the cavity which has depth, requiring material to be removed in layers. A computer-based image detection method is used for cutter -path generation and models that contain planar surfaces, general quad ratic surfaces, B-spline surfaces and compound surfaces can be treated . The B-rep solid object is transformed into an image as a grid-height model, allowing a three-dimensional object to be approximated by a tw o-dimensional spatial array. The cutter location (CL) data file is aut omatically generated from this spatial army. The height change of stoc k material in each grid is recorded in a two-dimensional array during the machining process and is utilized as an image for further roughing and verification. Efficient machining procedures are obtained by an a nalysis of cutting simulation, utilizing large cutter sizes for simple shaped portions in the first stage of roughing and then using small c utter sizes for complex portions and to remove uncut material left by the large cutters in a fine roughing operation. This approach allows a three-dimensional cutter path problem to be reduced to one of two dim ensions which is solved by image detection of cutting attributes. Copy right (C) 1996 Elsevier Science Ltd