NC-postprocessing and NC-simulation for five-axis milling operations with automatic collision avoidance

摘要

The off-line generation of collision free NC-programs for 4 and 5-axis milling is still time consuming and not optimal. Commercial CAD/CAM systems ignore the geometry and the kinematics of the NC-milling machine during tool path generation. Therefore machine test runs are essential to check the machinability of a tool path on a given five-axis milling machine. Real test runs can be avoided by using a NC-simulation program, however, most of these programs limit themselves to identifying collisions. In both cases, the CAM operator has to solve the collisions himself and this normally requires a number of iterations (tool path generation, post-processing, NC-simulation, test runs. This paper describes developments carried out at the K.U.Leuven, in which a generalised five-axis NC-postprocessor and a NC-simulation package have been integrated. This integration makes it possible to exploit fully the capabilities of the NC-postprocessor, the NC-simulation package and the five-axis milling machine. During NC-post-processing, the NC-simulation package checks each' tool position for collision and if this latter occurs, the NC-postprocessor immediately looks for alternatives without any operator interventions. The implemented automatic collision avoidance methods are searching for alternative combinations of machine axes positions yielding the same tool orientation, alternative clamping positions on rotary tables and tool lengths.