Effect of die width on spring back of electrogalvanized CR4 steel during air bending

Abstract

This study is an attempt for analyzing the effect on spring back due to changes in the die width during air bending of electro-galvanized CR4 steel. A universal testing machine, enabling recording of bending force and controlling of punch travel was used for conducting the experiments. A flexible die set with die width Wd = 40mm, Wd = 60mm and Wd = 80mm was used whose die width can be changed by simply changing a distance block. Die radius, punch radius and punch speed were kept constant. Galvanizing was done by electrodeposition method using alkaline non-cyanide baths. Different thickness of electro-galvanizing, Tg = 0 µm, 4 µm, 7 µm, and 10 µm were achieved by changing the timing of electrodeposition. An approach to vary one factor at a time was employed. Angles were measured by using optical profile projector and graphics. The Graphical method was used for analyzing the spring back. It has been witnessed that spring back increases with the increase in width of die for every punch travel and for non-galvanized as well as galvanized steels of different galvanizing thicknesses. An increase in spring back was observed when the galvanizing thickness was increased. The results are important for the tool engineers and process shop engineers for tool design and process control.