Increasing Accuracy of Industrial Robots in Machining of Carbon Fiber Reinforced Plastics

Compared to conventional milling machines industrial robots (IR) using serial kinematics bear great potential concerning cost-efficient and productive machining. However, the main disadvantage is their poor accuracy, caused by low structural stiffness and gear backlash. A novel robust approach for accuracy optimization of IR in edge milling is presented. This is highly relevant for manufacturing structural components made of carbon fiber reinforced plastics (CFRP). As a result of the long lever between the tool center point and the first rotational axis, backlash of the first gear mainly contributes to the overall machining accuracy of the IR. In order to eliminate this, the first axis is preloaded by a torque, caused by the gravitational force of the attached robot structure. Therefore, the IR is mounted on an inclined base. The performance of this setup is experimentally evaluated. Improvements of up to 50 % in terms of static stiffness, deviation of circular movement and contour accuracy in edge milling have been achieved.