感熱紙卷 of the paper roll has to be hard enough to guarantee a smooth unwinding at the one hand and has to be just hard enough to ensure a damage-free shipping and handling at the other hand.
A reliable measurement of the roll hardness profile is of critical importance in determining whether a roll is good or bad:
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.
Rolls that are wound too soft or too hard can cause serious problems when handling and this leads to loss in production. The reason for this variations in roll hardness are many, such as difference in moisture content, variations in the caliper (thickness) of the sheets or simply that the winding machine has not been set up correctly.
These variations are very difficult to detect without the aid of a roll hardness tester and if they go serious problems can result. Non-uniform hardness profiles can result in production downtimes for both producers and converters alike, making it one of the most important factor in determining whether or not a paper roll is good or bad.