Development of autonomous NC machine tool to realize NC programless machining operation for advanced manufacturing systems

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Required functions to develop an autonomous NC machine tool, which realizes NC programless machining operation for advanced manufacturing system, have been studied. Following research results were obtained.1. Machining simulation to predict cutting force and machining error in pre-process machiningA Virtual Machining Simulator (VMSim) has been developed for this purpose. The VMSim makes possible to predict cutting force and machining error for whole machining operation in advance. By using this function, the problem hidden in planning of tool paths and cutting conditions can be detected in pre-process machining for an autonomous NC machine tool.2. Real time tool path generation to optimize cutting conditions during in-process machiningA virtual copy milling system, which generates tool paths in real time based on copy milling principle, has been developed. The virtual copy milling system detects collision between a virtual tracer and a virtual master model, and generates tool paths to follow a sculpture surface for rough cutting during in-process machining. An NC programless machining operation can be achieved experimentally by the virtual copy milling system using conventional CNC machine tool.3. Adaptive control and feed back algorithm to avoid machining troubleA monitoring system to detect machining condition has been studied. In the monitoring system, rotational torque of both spindle and feed motors can be estimated from NC control signals based on the control theory. It is possible to detect cutting torque or cutting force without additional sensors, but further investigation is required to eliminate frictional torque of the motors.Furthermore, a feed back algorithm to avoid machining troubles has been studied. By using the virtual copy milling system mentioned above, even the axial and radial depths of cut beside the feed speed can be changed to avoid machining troubles. The effectiveness of the algorithm is verified using the VMSim mentioned above.