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-controlled machine tool. This technique is known as NC verification. The speed and the accuracy of NC verification software are two of the most important issues. In this implementation, an exact geometric model of the volume swept by a tool along a given path is first generated. The boundary profile of a general cross-section of the part is then created by means of a Boolean operation of the swept volume with the current profile. The operations and resulting 2D cross-sectional geometry are maintained using extended quadtrees. The latter introduces three extra node types (Edge, Vertex and Boolean) to the classical (Black and White) nodes of classical quadtrees. The extended quadtree maintains an 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 information for any feature in the machined part such as coordinates, distance 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