Anyone have the formulas for tonage for a stamping die handy? I need to start on the design of a two stage, progressive blanking and forming die for a project, but don't have my handbook or die design book where I can get to them right now. I know my material, the hole diameters and the total length of the part perimeters. What I need to do now is calculate the press tonage so that we can start the search for a press.
Craig C. snipped-for-privacy@ev1.net
The old rules were "25 tons per inch per inch" for straight lines and "80 tons per inch per inch" for holes. These are based on 50,000psi shear strength for mild steel and mechanical presses that have a weird tonage versus position curve. Example: for a 1" hole in 1/4" plate it would be 80x1"x1/4" = 20 tons. These also assume reasonable die clearances.
You can get by with less tonage if you put some shear on the various cutting edges. Works great on hydraulic presses, you can effectively punch several dozen small holes in sequence, each one taking only a small pessure. Same thing on a mechanical may stall it, NOT a good thing.
The form> Anyone have the formulas for tonage for a stamping die handy? I need to
Hey Roy,
Very interesting rules of thumb. (rule of thumbs??) I don't understand "ironing" an edge though. Wuzzat??
Take care.
Brian Laws>The old rules were "25 tons per inch per inch" for straight lines and
The OP asked about both punching and forming. Suppose in your first stage you take out a "U" shaped piece leaving a nice little tab that you want bent at 90 degrees to the main piece. In the second stage you have a ram that bends the tab over. For minimum press tonnage, you would put the ram edge 3x to 5x metal thickness over from the corresponding edge in the base die. Of course this may or may not wind up with the tab at
90 degrees and the bend edge will be quire rounded. So ironing is a third step where the ram comes down with very little or no clearance (after the metal thickness is deducted) to smear the edge and give a precise bend. Lots of friction here.Co> Hey Roy,
Hey Roy,
OK. Thanks. I know my buddy was doing some press size calculations for a little gadget he's making, and just thought that it might be something or info he could use. Interesting too.
Take care.
Brian Laws>The OP asked about both punching and forming. Suppose in your first
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