TAPPI TIP 0304-56 PDF

In the process of making corrugated board, there are several steps in the process that require precise applications of pressure between rolls, or consistent gaps between rolls in order to meter precise amounts of adhesive to the flutes. In order for these requirements to be met, rolls have to be parallel to each other and also must be as close to perfectly round as possible. Bearings or journals must also be operating in such a manner as to allow the rolls to turn as close to perfect circular motion as possible.
If a pressure roll is not rotating in a perfectly round manner, then as the roll turns against the corrugating roll there will be areas where the pressure applied to the singlefacer web at the rolls' nip point will be lessened. If the pressure is lessened enough, the singlefacer bond can be compromised and, thus, affect board quality. An adjustment to increase pressure to compensate for the problem could lead to another problem-pressure roll cutting of the medium and possibly box failure in compression and/or mullen (burst).