Paper Schmidt PS8000

Roll hardness is a roll feature that indicates the equality of the thickness profile and tension in a roll. In most cases, a relationship exists between the roll hardness and roll density. The higher the hardness value of...

Roll hardness is a roll feature that indicates the equality of the thickness profile and tension in a roll. In most cases, a relationship exists between the roll hardness and roll density. The higher the hardness value of a roll, the denser it is. Roll hardness measurements are widely used in the paper and plastic industries. Roll tightness and roll hardness terms are commonly used interchangeably in the paper industry.

Almost any material that must be wound into a roll can be controlled and measured for roll hardness.

In contrast to the thickness profile measurement, which measures the one wrap of the film only, the thickness equality obtained from measuring the roll hardness profile takes into account many thousands of wraps. Winding cannot make paper better, but in many cases the product quality can be much lower after winding, hence the correct control of roll profile hardness is one of the most important roll parameters.

The control of roll hardness enables the users to early spot the defects that appear during the roll winding process. The winding is also one of the last processes during the paper and roll making. Hence the highest cost...

The control of roll hardness enables the users to early spot the defects that appear during the roll winding process. The winding is also one of the last processes during the paper and roll making. Hence the highest cost of the broke papermaking process is at the end. All faults should be corrected where they first appear (in the process phase and position). It is never possible to totally compensate earlier fault with later correction.

Important take-home message:

Winding cannot make paper better, but in many cases product quality can be much lower after winding, hence control of the optimal hardness that match specific material and machine are of great importance for high quality and minimalization of material wastes.

Roll hardness profile is an important property of parent reels and customer rolls. A correct winding process can be monitored throughout a roll hardness profile measurement and leads to a roll of a high quality

Roll hardness profile is an important property of parent reels and customer rolls. A correct winding process can be monitored throughout a roll hardness profile measurement and leads to a roll of a high quality

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• If the roll is too soft, especially in the center, there will be handling damages such as starring and out-of-roundness. Additionally, there can be crepe wrinkles or telescoping.
• If the roll is too hard there can be bagginess and bursts.
• Too soft or too hard rolls tolerate less roll hardness variation than rolls with optimum hardness. There is always some (CD, Cross Direction) profile variation in the hardness, and it is important to find the optimum average hardness level to avoid roll broke.