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Ask the Stamping Expert: How can I get a die to run in two different presses?

Q: When I move a die from one press to another, the die runs fine in the first press but will not run in the second press. The presses are the same size, stroke, and speed range, although one is a few years older than the other. What can I do to ensure the die runs in both presses.

A: There are several steps you can take to try to solve this problem:

  • Check the total slide lift and parallelism. It could differ by 0.040 in. or more, because press tolerance can be different in presses of different ages.
  • Check that the press speeds (strokes per minute) are the same. A different speed will produce a different velocity of the die and press slide, causing a variable in the shut height of the press. A change in velocity will cause the part material to act differently.
  • Compare the parallelism of the bolster and slide, die and material lubrication, and feed accuracy on each press to ensure they are the same.
  • If you are using die setting blocks (stop blocks) (see Figure 1), make sure the press shut height is set correctly so they have the correct gap between them. Two stop blocks with an area of 2 by 3 in. can increase the load in a press by as much as 330 tons if they are coming in contact with each other. This makes a big different in press deflection.

If you don’t set the stop blocks correctly, the press can become severely overloaded. The following example shows how to calculate the possible overload. Of course, all die setting blocks are different sizes, so you can substitute the figures for your size and number:

  • Setting block surface area for four 2-in. blocks: 4 x 2 = 8 sq. in.
  • Mild steel yield strength: 55,000 PSI
  • Load to deform 8 sq. in. x 55,000 PSI = 440,000 lbs. = 220 tons
  • Load for four setting blocks: 220 x 4 = 880 tons