The effect of lubrication on die expansion during the deep drawing of axisymmetrical steel cups

This paper outlines experimental work conducted to determine the influence of lubrication on the expansion of a die ring during the deep drawing of axisymmetrical steel cups. The work was conducted in order to determine if the die expansion could be used as an indirect means of detecting and measuring the presence of a hydrodynamic lubricant film thickness, or as a gauge of the product surface quality in the process. Any indications of the presence of a lubricant film in this manner would allow assessment of current theoretical models and provide a measurement for use in the control of a widely used deep drawing process. The surface finish and wall thickness of the cups produced during the experimental work were measured and evaluated to determine any correlation with the measured die expansion. In conjunction with the experimental work, FEA simulations were developed for the tooling, using values for the coefficient of friction based on the lubrication regime of the process. The results of this work show the significant differences in die expansion obtained with different lubricants. These results are compared with those produced with FEA, which produce similar trends. The results support the concept that die expansion could lead to the measurement of lubricating fluid film thickness and may be used in conjunction with the lubrication regime as an indicator of produced surface roughness for process control.