Equipment, paper selection, control during operation and post-processing are all factors that affect the warping of cardboard, and solving the bending of paperboard is controlled for these factors. In terms of base paper, the moisture content is generally (8±1)% best, and the moisture spread of the entire width is uniform (the deviation is controlled within 1%), otherwise it is easy to form "S" shape or diagonally curved cardboard. In terms of paper distribution, the grammage of face paper and lining paper cannot be too different, generally should not differ by more than 50 grams, and raw paper with high moisture content and low moisture content should not be produced together.
1. Lateral upturning
The main reason for the lateral upturn of the cardboard is uneven moisture, and the cardboard is bent towards the side with high moisture, that is, the moisture of the inner paper is high. So how to reduce the moisture of the inner paper?
The first method is to reduce the amount of paste on the single-sided machine, and at the same time increase the amount of paste in the place of the paste machine. Because the two correspond to each other, increase here, decrease there.
The second method is to increase the moisture of the facial paper, spray water on the facial paper to increase its humidity, and also reduce the wrapping angle of the cardboard on the preheating cylinder, which can also improve the moisture of the facial paper.
The third method is to reduce the temperature of the hot plate, so that the moisture of the cardboard below is not easy to transfer upward, and at the same time can increase the speed of the car, and also solve the problem of the lateral upward tilting of the cardboard.
 

Based on the above several situations, the summary is as follows:
Causes and solutions of transverse S-type warping and diagonal warping
a. The moisture of the base paper is uneven, and the paper force is uneven. b. The base paper holder arm bracket is unbalanced, resulting in the inconsistent heating degree of the paper in the preheating cylinder wrap corner c. The installation level of the paper splicer.
Solution: Calibrate base holder arm level or splicer level, and add balance rollers to the most suitable.

Causes and solutions of lateral upturning
The temperature of the face paper is too high, and the temperature difference between the paper and the backing paper is too large, resulting in the shrinkage force of the backing paper after cooling is greater than that of the face paper.
Solution: a. Increase the wrapping angle of the backing paper and shrink the backing paper in advance. b. Increase the amount of facial paper glue. c. Minimize low-speed operation. d. Appropriately reduce the steam pressure of the hot plate. e. Reduce the corners of the facial paper. f. Appropriate paper spray.

Causes and solutions of lateral warpedia
The temperature of the backing paper is too high, and the temperature difference between the paper and the face paper is too large, resulting in the shrinkage force of the face paper after cooling is greater than the shrinkage force of the backing paper. (The principle and solution are the opposite of upturning)
Solution: a. Increase the corner of the tissue wrap and shrink the paper in advance. b. Increase the amount of liner glue. c. Minimize high-speed operation. d. Appropriately increase the steam pressure of the hot plate. e. Reduce the corners of the backing paper. f. Proper bottom spray.

Causes and solutions of longitudinal warpage
The tension of the facial paper and single tile in the paste machine is inconsistent.
Solution: Adjust the brake tension on the face paper or flyover.

Summery:
After the cardboard appears to be bent, how many measures are available?
First, the surface of the warped cardboard is wiped with water and then forward and reverse pressure is performed.
Second, the warped cardboard storage environment is humidified.
The third is counterpressure after steam injection. The newly produced cardboard has a high temperature, high humidity, and moisture is dispersed from the middle to the surroundings, at this time it is necessary to stack the front and back in time, and press it with a wooden board, push it to a ventilated, easy heat dissipation place to store for more than 4-8 hours, so that the cardboard is relatively flat after cooling.

What aspects do I need to pay attention to when stacking goods?
First, the cargo driver unloads the cardboard to be stacked flat on the pallet, and is not allowed to exceed the pallet. In principle, stacking crookedly can easily cause the cardboard to bend, leading to customer complaints.
Second, if the customer's storage conditions are in a ventilated place, the cardboard needs to be wrapped to prevent a large amount of moisture loss and cause bending and warping.