A Study of the Lubrication Mechanisms in Deep Drawing

Abstract

The oil film thicknesses between the tools and the workpiece and their changes during a cup drawing operation are analytically predicted to facilitate estimating the effects of the process variables on the lubricating conditions, including the blank holding speed, the time elapsed after setting the blank holder until the beginning of the punch penetration, drawing speed, lubricant viscosity, blank material and the geometries of tools and workpiece. It is experimentally shown that the greater is the ratio of the calculated oil film thickness to the maximum surface roughness which would result on the deforming workpiece separated from the tool by a very thick oil film, the smaller are the contact ratio and the friction between the tool and workpiece. The experiment also shows significant changes in the lubricating conditions on the die flat and on the die profile during the process.