High Accurate Robotic Machining based on Absolute Part Measuring and On-Line Path Compensation

Industrial 6 DOF robots is a platform for various machining processes due to its universality. A machining robot can perform any type of movement in space, the working space is relatively large and can be even extended based on a linear track (7th axis of the robot). Robotic milling is also a flexible and easily reconfigurable system and compared to conventional CNC machines, it is also a cost-saving alternative. However, there is still one main limitation concerned with a lower absolute robot accuracy, in comparison with CNC machines, caused mainly by a lower stiffness of the robot's serial kinematics and/or a backlash error resulting from robot's drives reversion. In this paper, we mostly present experimental results (milling) in order to demonstrate real limitations of robotic machining based on a Leica Laser Tracker system and a measuring arm CimCore. There is also described an approach for online robot path compensation based on the Laser Tracker absolute measurements in real-time where we reached the accuracy of finished products to be from tenths of mm to hundreds of mm.