THE BASICS OF COMBO CUTTING DIES
Written By Mark Batson Baril

A diecutting company recently approached us for an answer on this question.

We are die cutting 1/8" & 3/16" superwood (automotive hardboard) with 1 1/8" 4 pt. Serrated, edge hardened 14 tpi(tooth per inch) rule on a 3/4" die board. We have tried all kinds of stripping rubber using the 1/16" and 1/8" above the rule for Ejection. We are using a 350 ton Bruno press, cutting into a belt. We are Constantly having problems with our rule rolling over in random areas, sometimes from trim getting caught in the die and not stripping, sometimes for unknown reasons. We are losing valuable machine time and incurring excessive maintenance times on the tooling. Can you help me with some suggestions or point me in a direction that I may be able to contact someone who may be able to help? I am desperate to find the solution to this problem. If you would require any further information you can contact me at:

After talking with the diecutter about this and gathering a few more facts, I have a few suggestions to make. As always, inquire with as many people in the Industry as you can. At least, you will get a couple of answers/technicalities you may not have thought of before. At most, you will find someone who has dealt with this exact problem before.
  • I would suggest getting in touch with A Technical Expert over at your current ejection material supplier. Someone that really knows their stuff. Present the same question to them.
  • I would suggest the same of your Machinery producer. They must have other customers doing the same thing you are and they may be able to add some suggestions.
  • Talk with your current rule supplier about the problem. What type of rule are you using? The general specs. are 4 point 1.125" 14 TPI Hard - but who is making it for you? I have seen many cases where a change in bevel, TPI, Hardness or even serrated tooth profile can make a huge difference to the cutting pressure needed.

Die changes could include the following:

  • Change future layouts to increase your web space to more than your current 3/4". Anything more may help and may not cost you anything in material usage.
  • Bridges are sometimes a major cause of rule fatigue. Look at your bridge patterns on future layouts. You said that your bend-overs are typically happening at tight space areas. Perhaps the flex is starting at the bridges in this area. The common theory is to over support these areas with lots of bridges. By eliminating or reducing the number of bridges in these areas you may actually increase the strength of the die during the impression.
  • Also, what is the size of the bridge you are using? I have found that smaller bridges in bigger quantities is usually a good thing. Also - the rule can be dramatically strengthened by not only reducing the width of the bridge but also by reducing the height. If your using a 3/4" base, try etching it down to 5/8" at the bridges and reduce your bridge size to build strength. Usually the base strength is not compromised enough to make a difference and if it is, again increase the quantity.
  • We have seen a few cases where it helps to add a solid material to the top of the ejection material. Typically a piece of hardboard, hard plastic, or other hard but thin material is glued to the surface of the rubber. This creates a “flat top blanking” like operation that helps to push the entire part out of the die in one shot, evenly, and with greater force than just plain rubber. It helps to reduce the number of areas where the parts are sticking as well and should maximize your running speed by getting those parts out of the die fast!

    I believe that a combination of all of the items above will help to get this press moving at full blast. I hope this works to at least start your improvement process. Good Luck!

    As it turns out this is a real success story that worked it’s way through the IADD’s technical answer system in the past couple of years. The suggestion about the bridges seemed to intrigue the diemaker and press operator the most and that area was chosen as the logical starting point. All the bridges in the tight areas were removed completely. The improvement was immediate and dramatic as the rule was strengthened and the fatigue roll-overs where eliminated completely! The press was back up and running at full blast with no further tinkering as this long term problem came to an abrupt end.

    Please contact Cut Smart if you would like more information on this subject.

  • Email: engineering@cutsmart.com
    Phone: 1 800 465 4141

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