The most common paperboard problems and Solutions

Common paperboard problems and solutions

now the manufacturing process of corrugated boxes is becoming more and more sophisticated, but there are still many quality problems in actual production. For the majority of carton manufacturers, solving the problem of paperboard is the key to improve the quality of finished cartons

"washboard" paperboard

with the undulation of corrugated core paper, the face paper bounces unevenly on the surface of the paperboard, which is shaped like "washboard", also known as "washboard" paperboard. Its forming reason is:

the viscosity of the paste is too large, or the amount of paste is too much. When the ridge peak is bonded with the face paper under pressure, the excess paste is extruded and attached to both sides of the ridge peak, forming a paste area much wider than the actual need on the width of the ridge peak. With the drying of the paste solution, the face paper is pulled down on both sides of the ridge peak, forming a "washboard" and exposing the ridge marks on the surface. The paper with higher gram weight has greater rigidity, which can resist this shrinkage tension, and the subsidence is less. Therefore, when using thinner or smaller gram weight tissue paper, we should pay attention to reducing the amount of paste, that is, we should reduce the gap between the paste roller and the scraping roller, so as to reduce the occurrence of "washboard"

after the corrugating roller is worn, its corrugating peak radius increases. Therefore, it is easy to absorb more adhesives, which will easily lead to the "washboard" phenomenon

the speed of the paste roller is inconsistent with that of the lower corrugating roller, so the adhesive is concentrated on one side of the ridge shoulder, causing the face paper to shrink on one side

the moisture content of the face paper is too high, which causes the shrinkage and subsidence of the face paper after the adhesive is dried

cardboard warping

cardboard warping refers to the fact that the cardboard is convex or concave in a large range. There is a kind of cardboard warping called "positive warping", also known as "upward warping", that is, the cardboard bulges to the side of the face paper. The opposite is "reverse warping". One side is convex and the other side is concave, which is "S-shaped warping", and the warping unfolded with the diagonal of the cardboard as the axis is "twisted warping". The warping axis is parallel to the corrugated direction, which is called "warping in the length direction". Using warped cardboard as carton, the molding cannot be square, which affects the appearance and the compressive strength is unstable. Warped cardboard is not easy to accumulate and cannot enter the printing machine smoothly, which seriously affects the printing chromatic effect and the accuracy of slotted die cutting

the root cause of warping is the uneven shrinkage of paper, which is caused by the different degree of expansion and contraction of each component of paperboard. The degree of shrinkage varies with the moisture content of the paper. When the surface paper and the inside paper of the cardboard have different degrees of expansion, it is easy to cause the cardboard to warp. Compared with the thin and low weight paper, the thick and high weight paper has a relatively stable degree of elasticity and is not easy to deform. Therefore, when the thickness of the face paper and the inner paper is different or the weight of the gram is different, the paperboard is easy to warp. Therefore, in the paper distribution stage of the carton design, the weight of the face paper and the thickness of the inner paper should be equal or relatively close

in production, the shrinkage and deformation of paper can be controlled by heat adjustment to reduce the warpage of paperboard. The cause of "positive warping" is generally that the lining paper and single corrugated paper are too wet and the face paper is too dry. Therefore, the drying of the lining paper and single corrugated paper should be strengthened to reduce the preheating of the face paper. Proper measures, such as increasing the preheating area of corrugated paper and lining paper on the single-sided machine, reducing the temperature of the hot plate, appropriately increasing the vehicle speed, reducing the heat transfer, reducing the paste amount on the single-sided machine, can largely avoid the warpage of the paper. The reason for "reverse warping" is just the opposite. It is because the single-sided corrugation is too dry and the facial paper is too wet. The opposite method can be adopted to control it. "S-shaped bending and warping" microcomputer peeling force testing machine often causes the base paper to shrink seriously because the edge of the paper is too wet, which can be compensated by increasing the preheating time of the base paper; In addition, the reason for warping is that the weight difference between the upper and lower paper is too large. You can adjust the paper distribution to reduce this phenomenon. "Distortion and warpage" are caused by poor quality of base paper, uneven distribution of moisture everywhere, uneven distribution of hot plate temperature, etc. these aspects should be rectified accordingly. "Bending in the length direction and grasping the packaging waste treatment and resource recycling and reuse" is caused by improper tension, which can be adjusted

the above warping problems can also be improved by sprinkler. For the warped paperboard that has been produced, it should be turned over immediately. Taking advantage of the characteristics of high temperature and high humidity when the paperboard comes out, stack it upside down in time, press it with a wooden board, and then push it to a ventilated place to dissipate heat for 4 ~ 8 hours, which can make the paperboard relatively flat

high and low corrugation

vigorous development "high corrugation" refers to fully formed corrugation, that is, the corrugation height meets the standard requirements or is consistent with the tooth depth of the corrugation roll; The "low corrugation" is the corrugation that is not fully formed, and its corrugation height is usually lower than the standard value or the tooth depth of the corrugation roll. When the core paper is rolled and bonded with the lining paper, and the high ridge and low ridge exist at the same time, it is called "high ridge and low ridge"

low corrugation is one of the reasons that affect the quality of corrugated board. Due to the small height of the low corrugation, it has poor or no adhesion with the face paper, which affects the bonding strength of the board, reducing its edge pressing strength and flat pressing strength. Moreover, due to the appearance of low corrugation, the surface of the face paper is uneven, which affects the appearance and printing effect

the causes and solutions of high and low corrugations are roughly as follows:

the corrugating rollers are not parallel, the bearings at both ends are worn, and the corrugating rollers vibrate when running at high speed. Check and adjust the parallelism of the corrugating roll, adjust the bearing clearance or replace the bearing, reduce the speed and avoid the resonance zone

the pressure between corrugating rollers is insufficient, so the pressure should be increased

there is waste paper or other impurities in the grooves of the corrugating roll, and the impurities should be removed

too high or too low moisture content of corrugated core paper will affect corrugated forming. When it is too wet, the preheating area should be increased, and when it is too dry, the spray amount should be increased

the corrugated core paper drum is not round and rotates unevenly during operation. It is necessary to increase the tension or replace the base paper

corrugation

corrugation refers to the inclination of the corrugation to one side. The inclination of the corrugation leads to the insufficient thickness of the cardboard and the decrease of the strength. When the corrugated board moves in the processing process, it is pressed, rubbed and dragged, so the rollers everywhere must be parallel to the processing surface and kept well lubricated, so that when the rollers are used, they must be careful and rotate flexibly to reduce friction. The specific causes and solutions of corrugation are as follows:

the parallelism between the upper and lower corrugating rollers and between the lower corrugating rollers and the pressure roller are not parallel or the pressure is too high. The parallelism between the rollers should be checked and the pressure between the rollers should be appropriate

the tension of single-sided corrugated board is too strong

when gluing single-sided corrugated board, the gap between the riding roller and the pasting roller is too small

the moisture content of corrugated core paper is too high, so the preheating area should be increased to reduce the amount of spray

there are sundries on the hot plate, which need to be removed

line pressing burst

when the corrugated board is folded, the line pressing part is broken. The main reasons and solutions are as follows:

the gap of the line pressing wheel is too small, and the gap should be adjusted

the crimping wheel is not round, so it needs to be replaced

the line pressing axle is bent, and the line pressing axle needs to be replaced

--- carton Technology