（1） There is a great difference in the beating degree of each layer. The water content of the pulp layer is not consistent, and the foaming part generally appears after the pressure zone between the two pulp layers with a great difference in beating degree. Treatment: control the beating degree of each pulp layer within 10sr, or increase the water level difference between inside and outside the net in the pulp layer with high beating degree, and strengthen the dewatering capacity of vacuum suction tank;
（2） The pressure of the couch line is not adjusted properly. Treatment: appropriately increase the line pressure of front couch roll at the foaming part to reduce the foaming part
The linear pressure in the pressure zone;
（3） When the pulp volume and liquid level of the pulp on the net, the water level difference between the inside and outside of the net are not properly controlled, and the vacuum degree of the vacuum suction tank is too low, the moisture content of the wet paper formed by the pulp layer is very different, bubbles will be produced in the net. Treatment: adjust according to the situation
Festival;
（4） The dirt or oil block on the part of the mesh and the woolen cloth results in local dehydration and poor air permeability, which makes the air between the woolen cloth and the paper more stable. The water cannot be discharged well. In this case, foaming occurs at the preload. Treatment: cleaning copper mesh (plastic mesh), wool cloth;
（5） When there are dents on the couch roll or mesh surface, excessive air, and water will be brought in, and bubbles will be formed after pre-pressing. Treatment: more
Change couch roll or net;
（6） When the suction scraper of the couch roller is partially jammed, the water retaining cloth is uneven or has holes, the water pressed out will make the wet paper "return"
The phenomenon of "tide" destroys the local interlaminar bonding, and produces bubbles in the backpressure zone, and even embossing in serious cases. Treatment: cleaning, adjusting suction scraper, or changing water retaining cloth; Adding a reverse suction vacuum water tank behind each cage couch roller can reduce the moisture of each layer of wet paper, which can reduce the phenomenon of blistering and embossing.
（7） The drying temperature curve of the dryer is not well adjusted, the temperature of the dryer rises sharply, and the water vapor generated inside the paperboard can't be controlled very well
Fast escape, stay in the weak fiber adhesion between the layers of paper, resulting in cardboard delamination. Treatment: adjust the drying temperature curve of the dryer, the temperature of the first two dryers should not be too high, generally 90 ~ 95 ℃ is appropriate. After that, it gradually increased to 120-125c.