Auto-recovery from machining stoppages based on STEP-NC
Machining stoppage occurs from time to time due to various reasons. For the current CNC system using G/M code as part program, to recovery from the stoppage, the operator needs to scroll the part program to find the specific lines where the stoppage happens and make changes to it, because the part program only contains low level machining information, i.e. tool-paths. This process highly relies on operator's experience and is time-consuming. STEP-NC as a new standard for part program defines the machining of a workpiece by workingsteps of machining features, which include geometry information and machining strategy for each feature. Helped by that information in STEP-NC part program, the system is able to plan the retracting toolpath, use different strategies to recover from the stoppage and even regenerate new toolpath for an alternative cutter if the same one is unavailable. When using traditional CNC system, the machining of unfinished workpiece cannot be resumed by another machine tool due to the G/M code's hardware dependency. However, the feature-level machining history information can be stored in STEP-NC file and transferred to another machine, which will be used for process planning and toolpath generation. After relocating the workpiece coordinate system in the alternative machine, the machining can be resumed.
Includes bibliographical references