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What is the most important thing to remember when using bowed rolls?


Maintain the proper geometry!

Bowed rolls can be a very effective and aggressive web spreading device. However, to get the most from your bowed rolls it is extremely important to maintain proper geometry. Here are some rules of thumb when applying bowed rolls:

  1. Almost all of the spreading takes place in the entry span to the roll. The longer your lead-in distance (unsupported web distance leading into the bowed roll) the more spreading you will get. The lead-in distance should be roughly double the lead out distance (unsupported web distance leading out of the bowed roll).
  2. Keep your lead out distance to a minimum. The smaller this distance, the less chance you will have of wrinkles returning to your web.
  3. Keep wrap angles to a minimum. Often times when I am in the field and see bowed rolls that are not operating properly or they are causing more trouble than they helping, it is because wrap angles are too great. My opinion is (and I have had many people argue with me about this) that wrap angles around bowed rolls should NEVER exceed 30 degrees.
  4. One last word about bowed rolls; when applied properly they will effectively remove wrinkles. But the question is, what are you doing to your web by utilizing a bowed roll? The potential problems with bowed rolls are not that they do not take wrinkles out, they do. The problem is that the web tension profile as the web travels over the bowed roll is not even. Due to the raised center of the bowed roll, you will deliver added tension to your web in its center. How will that affect your material? Will your material be distorted by your bowed roll? That is the question to ask when using bowed rolls to remove wrinkles.


**DISCLAIMER - A great deal of time has been invested in the development of our weekly tech tips. To the best of our knowledge, they are accurate. It is up to the user to verify all results.

THE AUTHOR ASSUMES NO LIABILITY CONNECTED WITH THE USE OF THIS INFORMATION OR THE RESULTS OBTAINED FROM IT.



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