Die Science: How to destroy a press

It’s amazing how many stampers and tool and die shops negate the importance of the press. Shops often “maintain” a press when it stops working. In other words, they repair the press, but they don’t maintain it regularly.

I could have just as easily named this article “How to select and care for a press.” However, based on my personal experience, people are more interested in what they are doing wrong than what they are doing right.

My article may seem to be a bit cynical and sarcastic, but I am sure many of you reading this will say to yourselves, “Yep, that’s us,” “Yeah, we do that,” and, of course, “We never do that!”

Whether or not you recognize your shop’s actions in the following list, here are the actions to avoid whenever possible:

1. The Press

• Make sure that you select a press that doesn’t have enough tonnage to perform the work.
• Choose the tonnage of the press based on the total tonnage needed and not the tonnage available throughout the stroke. Just ignore those funny tonnage curve charts that come with the press manuals.
• Use a press with maximum deflection, especially when great tonnage and precise alignment are necessary. Use a gap-frame press for high-tonnage,precision alignment jobs.
• Choose a press based on the bed size alone.
• Choose a deep-drawing press for high-shock blanking operations with heavy metal.
• Don’t worry about the energy available for the work to be done.

2. Press Maintenance

• Never lubricate the press ways or gibs; ignore the lube pump warnings.
• Just assume the ram is parallel with the bolster and never check it.
• If you do check parallelism, do so when the press ram is not under load.
• Avoid checking for slop between the gibs and ways.
• Avoid checking stopping times, and avoid inspecting the clutch and brakes for wear.

3. Die Setup

• Ignore the counterbalance settings on the press. This will likely result in increased shock of press components and poor ram-to-bolster alignment. Adjust the counterbalance improperly to increase power consumption and clutch and brake wear.
• Offload the press ram as much as possible. Be sure to put high-tonnage dies as far to the left or the right of the bolster as possible. This will cause the ram to tip and result in severe uneven wear on the gibs and wear plates. It also will cause the ram to slop back and forth. Your press will be out of spec in no time at all.
• If possible, make sure that the dies stick out beyond the press ram and bolster. This amplifies the leverage exerted on the ram and is the best way to offload and damage your press.
• Put all of the required force into a localized area of the bed. This will cause the bolster and ram to twist and bend severely, helping you to make unacceptable parts and quickly reducing the accuracy and life of your press.
• Adjust the shut height of the press based on the sound it makes on bottom dead center. You also might try the “when I see oil squeeze out from the press frame joints, I know I am down” method.
• Don’t double-check clamps and bolts for tightness.
• Bypass or turn off all tonnage overload monitors and die protection systems.

4. Die Design

Make sure that all of your cutting dies are designed without cutting shear so that the shock load to the press is maximized. Also make sure that all of your cutting punches enter at the same time. Doing so will not only increase the force and shock on punch impact, but it also will increase the negative tonnage achieved. Do this and you will well be on your way to a sloppy press.

5. Troubleshooting and Training

• When troubleshooting, just lower the ram and hit it harder when you have a forming problem.
• Don’t spend any time educating press operators.

Condescending? Cynical? Yes, probably. However, the objective of this list is not to criticize or condemn, but to shed light on some of the everyday practices which, over time, can and do destroy presses.

The press is just as important as the die. It must be properly selected and maintained. The tooling must be properly set up and calibrated. Certain practices, such as offloading a press, sometimes are unavoidable. But you need to be aware that doing so may warrant more frequent press maintenance.

So, for once, I’m asking you to avoid doing what I say … that is, unless press destruction is your goal.

Until next time … best of luck! Art