PAPERSCHMIDT - APPLICATION

The need for Paper Roll Hardnesss Testing

Rolls that are wound too soft typically may go out of round during transport and storage. If this happens it causes irregularities whilst unwinding and the only way to compensate for the effects is to slow down the speed of the unwinding machine leading to a loss in production. Rolls that are wound too tightly can lead for example, to bursts within the roll, corrugations on the surface as the web is stretched too tightly, etc.

These variations are very difficult to detect without the aid of a hardness tester, and if they go undetected, serious problems can result. Above all, “it is typically the variation in hardness across a given roll that relates most directly to such converting issues with soft edges being perhaps the biggest contributor.” (TAPPI T 834 om-07 "Determination of containerboard roll hardness") See more here (Wound Roll Structure): http://paperindustryweb.com
   

How to measure

Measuring the roll hardness profile with PaperSchmidt is a simple, rapid procedure. Each factory has its own procedure, but the general procedure is always the same. Begin at one end of the roll and not too close to the edge. The drawing below shows the minimum distance from the edge and recommended distances between impacts as recommended by TAPPI T834 om-07. To carry out an impact, place the hammer perpendicular to the paper roll. Push the hammer against the surface of the roll at a moderate speed until the impact is triggered. Repeat this procedure to obtain a profile across the entire roll in the CD direction.