Development of Camera System for Monitoring Robotic Polishers

Abstract Industrial robots have been in increasing demand in recent years, although their lower positioning accuracy and velocity controllability (compared to CNC machine tools) makes it difficult to adopt them in machining processes such as milling. However, precision polishing using compliant tools, fluid jets, etc., belongs to the class of time-dependent processes where the amount of material removed depends on the surface feed rate of tool influence on the workpiece. Therefore, there is a possibility to maintain high accuracy even when using industrial robots, so long as the velocity profile is well predicted. In this paper, the attitude and motion of an industrial robot tool center point is estimated using a stereoscopic high-speed camera setup. 3 light markers are mounted above a fluid jet polishing nozzle attached to the robot end-effector. Their positional relationship to the tool center point is ascertained by collecting posture data while maintaining a precision ball at a fixed location with an R-test device. Next, raster paths are generated and the robot motion is recorded with the cameras. This data is used to predict the surface profile to be generated when polishing a BK7 optical window. Actual polishing confirms a good correlation, within 10 nanometers, between measured and predicted material removal.