Influence of Die Shape and Configuration on the Elastic Deformation of Die in Cold Forging

Abstract

A measurement method by the combination of a gap-type capacitive displacement transducer and the strain gauge method is applied for measuring the elastic deformation of inner surface of die in cold forging. A 1-mm-diameter hole is bored radially to the depth of about 1.2 mm from the inside surface of a die container and a steel pin is placed in the hole for detecting radial displacements near the die-workpiece interface. The coil spring pushes the detection pin inward in the radial direction, while the radial displacement of the die-workpiece interface pushes it outward. The detection pin head faces the capacitive transducer head for measuring variations in the gap between the head of the detection pin and the capacitive transducer head. The radial displacement of the capacitive transducer head is simultaneously measured by the strain gauge method for adjusting the measurement obtained from the capacitive transducer. This combined technique is applied to measure die deformation in the backward extrusion of pure aluminum. The measurement is made at 8 points in height direction simultaneously and the displacement distribution over the die-workpiece interface is obtained. We make measurement under various die/punch shapes and configurations. In conclusion, we demonstrate the validity of this measurement method.