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Monday, May 4, 2015

Why Measure Roll Hardness?

By taking hardness readings across the roll, uneven, too soft or too hard winding can be detected and the roll can be rejected. This minimizes the risk of complications e.g. during the printing process on paper.

There are several reasons why a ROLL PRODUCER may want to test the roll structure of shipping rolls (or jumbo reels):

  • To determine the cause of specific roll defects such as crepe wrinkles or corrugations
  • As an aid to establishing the winding criteria of a newly installed winder or major rebuild of a winder or reel
  • As a quality control tool to check rolls before they are shipped to an end user

A CONVERTER may want to check shipping rolls received from a roll producer:

  • To determine how specific roll irregularities effect the efficiency of their machine
  • To supply creditable data to enable the roll producer to understand and resolve his concerns.

Rolls that are wound too soft typically may go out of round during transport and storage. If this happens it causes irregularities while 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-12 "Determination of containerboard roll hardness")

There are several roll hardness testers available to the Paper Industry. The ACA Systems RoQ uses technology developed specifically for the Paper Industry.  It has the most current technology, user interface and fine resolution.  This device can determine the hardness of large rolls of paper, film and foil. It provides fast, accurate, non-destructive hardness profiles of rolls to assure smooth and efficient printing. As stated above, rolls that are too hard, or too soft, rolls that are unevenly wound, or rolls with different moisture contents can cause difficulties during the printing process.

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