Corrugated board S-warping solution

Up warping and down warping are simple warping, S warping and diagonal warping described later are very troublesome warping. When this kind of warpage occurs, it can be piled up by flipping 180 degrees in groups of 10-20 sheets at the production line. At the same time, when such warpage is serious, in addition to the above-mentioned method of accumulation, a heavy object must be used to flatten the warpage. Otherwise, it will cause obstacles in the subsequent box-making process.
The cause of S-warping is:
(1) The horizontal wet stripe on the hang-up roll.
(2) The moisture on the edge of the liner of the liner is large.
(3) The heating temperature of the double-sided machine is not uniform.
According to the United States CID experiment, the above (1), (2) is the main cause of S-warping.
The upper half of the ordinate represents the percentage of paper moisture, and the lower half represents the warpage of the paperboard produced. The abscissa indicates the web width width (inches). If the wet spot is on the operation side of the corrugating machine, a warp of warpage of 0.8 occurs on the operation side. If the web is used in reverse, the operating side decreases by 0.3 from the warpage before flipping by 0.8; but the transmission side changes from 0.2 to 1.0, which confirms the moisture wet spots on the web banner to the corrugated cardboard. Partial warping is influential.
The relationship between the width of the wet spot in the direction of the noodle base paper banner and the degree of excess moisture is related to the warpage. CID uses the following figure to show the relationship between them. That is, the relationship between the width of the wet spot and the average moisture of the base paper is such that when the product of the percentage of excess moisture reaches 40 or more, the warp degree can reach 1 or more, and unacceptable warping occurs (for example, the width of the wet spot is 10 in. When a part of water contains 4% of the average moisture content, uncontrollable warpage can occur.
The main key to overcome the S-type warping from the above three items is that the moisture content of the base paper should be even, and then the control temperature of the double-sided machine should be even.