Hydraulic Press Products – Shock Dampers

Have you ever been in a metal stamping facility and heard something that sounds like a train running into the building every time the press cycled? If you have, what you are hearing is an event called reverse tonnage and it is tearing up the press. In this short explanation, we will attempt to explain Reverse Tonnage also known as Snap-Through in a metal stamping press. Reverse tonnage is the undesirable results of cutting and blanking operations. In the stamping process, the moment the punch meets the material, the press frame begins to deflect until the press has built up enough force to exceed the shear strength of the material and the punch breaks through. When this happens the press frame will release the stored-up energy and snap back past its original position or resting position into a compression load.

The press frame and components that are designed to function in a tension load are now in a compression load condition and all of this will occur in less than 20 milliseconds. At the instant of breakthrough during blanking, the press and dies are subjected to severe stress. This compression load condition on the press frame is called reverse tonnage and it can damage your press.

The conventional industry standard is to have presses designed to accept a reverse tonnage load that does not exceed 10% of the maximum forward capacity of the press. In other words, the maximum allowable reverse load for a 600-ton press is 60 tons. So, anything over 60 tons, you risk damaging your press.

So, what happens when we have too much reverse tonnage?

  • We see fatigue failure of press components–especially in the slide connection area but also main frame parts. Sooner or later, this could result in damage to bearings, seals, gibways, etc.
  • You could have premature wear of punches and die components.
  • You can see foundation issues along with a high noise level.
  • Components like bolts, air, and hydraulic lines and become loose causing unnecessary leakage.
  • Electrical malfunctions
  • High snap-through will affect the operator and could cause fatigue, foot, ankles, knees, hips, and even back problems.

There are several ways to reduce reverse tonnage in a blanking operation:

  • You can change raw material to a softer and thinner type if the job allows for it.
  • Maintain punches to limit the applied tonnage or step the punches.
  • Reducing the press speed helps, but it increases the production time.
  • You could also place the tooling in higher tonnage capacity presses.

Many times, these reduction methods are not practical or may only minimally reduce the reverse tonnage on these heavy-hitting jobs. However, the hydraulic Shock Damper is the solution. Hylatechnik developed the hydraulic Shock Damper over 45 years ago and stampers from around the world have been protecting their equipment by using them.

Hylatechnik Shock Dampers are designed to protect the press and tooling from snap-through loads. The Hylatechnik dampers will reduce or eliminate reverse loads, floor vibration, noise, and will increase tool life as well as forward tonnage in many applications.

Applications include hydraulic presses, mechanical presses, and press breaks. The shock dampers are not limited to the press size. They can be used on the largest of machines.

Additional benefits of the Hylatechnik Shock Damper are:

  • Increase press speed
  • Use full press capacity
  • Reduction in foundation vibration – reports have shown a reduction in floor vibration of nearly 40%
    Reduction in noise levels
  • According to AIDA Americas research, they found that the reverse load can be reduced by 83%-99% in some of their presses by using the Hylatechnik Shock Damper.

To see the positive effects of the Hylatechnik Shock Damper on your press call the pros at IC-Fluid Power to arrange a demonstration. We can be reached at (419) 661-8811 or us@icfluid.com.

 


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