DIMENSIONAL VERIFICATION OF NC MACHINING PROFILES USING EXTENDED QUADTREES

Computer modelling and simulation technology assists in validating NC (numerical control) programs before they are executed on a computer-co ntrolled machine tool. This technique is known as NC verification. The speed and the accuracy of NC verification software are two of the mos t important issues. In this implementation, an exact geometric model o f the volume swept by a tool along a given path is first generated. Th e boundary profile of a general cross-section of the part is then crea ted by means of a Boolean operation of the swept volume with the curre nt profile. The operations and resulting 2D cross-sectional geometry a re maintained using extended quadtrees. The latter introduces three ex tra node types (Edge, Vertex and Boolean) to the classical (Black and White) nodes of classical quadtrees. The extended quadtree maintains a n exact and economical representation For a 2D object while retaining much of the simplicity of Boolean operations for classical quadtrees. The verification system supports both flat- and ball-end milling tool geometries, with both cylindrical and tapered sides. The dimensional i nformation for any feature in the machined part such as coordinates, d istance and radius can be easily detected. In typical test cases, the system can process 400-500 lines of NC code per second on a 486/66 PC. Published by Elsevier Science Ltd