Study on eccentricity in cold cup extrusion. 1st report. Measurement of punch load eccentricity and lateral force.

Abstract

Punch load P, eccentricity in punch load (deviation of punch load center from the punch axis, e^^→P) and lateral force F^^→ exerted on the punch head are measured by a newly developed test apparatus of forward cup extrusion. The elastic deflection of the punch, (OPOP)^^^→, is calculated from P, (eP)^^^→ and F^^→, then, eccentricity of the outer and inner diameters of the cup, (OdOP)^^^→, is evaluated by (OdOP)^^^→=(OdOP)^^^→+(OPOP)^^^→, where (OdOP)^^^→ is the initial eccentricity of die and punch. Though the directions of (eP)^^^→ and F^^→ did not necessarily coincide with the direction of (OdOP)^^^→ and varied (rather complicatedly) during the process, the calculated eccentricity of the outer and inner diameters of the extruded cup almost coinsided with the measured one.