Robot Grinding and Finishing of Cast Iron Stamping Dies

Abstract

This paper describes a method for finishing cast iron stamping dies. The task is to remove tool marks in the form of grooves and cusps left by a ball-end milling tool. The bottoms of the grooves represent the desired final surface profile. The method consists of using a closed-loop force-controlled robot with a flexible grinding disk coupled to a means for measuring the height of the partially ground cusps. Measurement is particularly easy, accurate, and sensitive if the tops of the partially ground cusps are flat, a condition that is not easy to obtain; otherwise accurate measurement is a chore. The Taguchi method is used to determine process parameters (grinding grit size, feed speed, disk speed, disk inclination angle, etc.) that yield flat tops. This grinding strategy has proven successful. A smooth, regular, and accurate final shape is obtained in spite of the relatively poor position accuracy of the robot. The measurement strategy has not been implemented yet but it appears feasible based on preliminary experiments.