The effects of using coated tools in the deep drawing of aluminium

Abstract

The performance of titanium nitride coated punches and dies in deep drawing is compared with that of uncoated tools, in terms of two parameters: the maximum punch force, and the limiting draw ratio. The effectiveness of titanium nitride coatings on tools with different corner radii is studied also. Deep-drawing experiments were conducted on aluminium using all possible combinations from two similar sets of tools: one uncoated, the other coated with titanium nitride. Both sets consisted of punches and dies with different corner radii. It was found that the titanium nitride coated dies reduced the maximum punch forces by 7.45 to 13.40%. The coated dies also improved the limiting draw ratios by about 4.59%, with the combination of uncoated punch and coated die yielding the largest limiting draw ratios. The punch forces were also reduced when the punch and die corner radii increased. The limiting draw ratios were improved with the increase of die corner radius, while punches of profile radii 6 to 7 times the blank thickness gave the highest limiting draw ratios. The experimental results agreed reasonably well with the theoretical predictions obtained by an approximate solution proposed by Duncan and Johnson.