Sheet metal punch tool-overbend

[gpot]

I need to make a sheet metal punch tool to punch 3 radii into a sheet of aluminium alloy, 0.5mm to 1mm thick, 350mm by 310mm.

The profile is such that the largest radius is in the middle and tangential downwards, the other 2 radii are symetrically on either side of the main radius and in the oppistie direction. ( something like a very shallow/wavy letter "m&quot

I need to know how much you have to overbend the required radii so that the sheet will keep its new profile after punching? is their a formula or ratio to use?

 

[TVP]

I am not aware of any standard ratio. The degree of springback is a function of the alloy, thermomechanical history (rolling, heat treatment, etc.), tool geometry, and forming temperature. There have been a number of technical papers published in the past few years (SAE, Journal of Materials Processing and Technology, etc.) that have data on springback of formed aluminum parts. I recommend searching the SAE website and Scirus:

http://www.sae.org

http://www.scirus.net