Metrology enhanced robotic milling – A practical application on automotive tooling

Abstract

Drilling or milling an industrial object (using tactile treatment) is one the most difficult tasks for robots if it comes to accuracy. Force feedback influences create positional deflections of the robots tool center point and therefore inaccuracies visible in the resulting product. One strategy to avoid or compensate these positioning errors is to improve the robot by an external measurement system. This system is normally aligned to the workobject and its uncertainty is neglectable compared to the robot. In this presentation a practical realization of this strategy is shown by an application for automated milling of clamping tools for welding tasks in the automotive industry. Common procedure for these clamping tools today includes a time-consuming iterative process of measurement and shape adaption until the desired and needed configuration of every single clamp of the tool is reached. In the presented solution, a 6DoF laser tracker is used to measure the clamp planes as well as the robot tool. Special measurement and positioning strategies facilitate a one-shot, fully-automated robot milling machine with all advantages and flexibility of modern robotics. We will discuss both the achievable accuracies as well as the productivity gains that this system is able to realize.