Lulu: refers to the height of the flute that can be clearly seen on the paper. The bottom paper of the cardboard produced by general manufacturers has exposed corrugation, which is normal, but the exposed pits should not exceed 3mm and the surface paper should not be exposed.
Lack of material: refers to the width of the cardboard is not enough. The reason for the lack of material may be insufficient base paper, shrinkage of base paper after heating, and wrong edge (also called uneven paper edge). These reasons may be misalignment of the barge, displacement of the paper holder, and unevenness of the end surface of the base paper. In addition, it is also related to the tension of the face paper, bottom paper, and pit paper during operation.
Dew pit: Refers to the pit pattern that can be clearly seen on the paper surface, which is caused by the lack of material in the top paper or bottom paper.
Collapsing: It means that the peak flute of the pit paper is crushed and collapsed due to the pressure exceeding its bearing capacity. The cause of the collapse may be that the pit machine is not running normally, and the adjustment is not normal (in principle, the machine should be tested every day), and the sundries in the double-sided machine are also related to the pressure on the pit paper (such as the paste wheel pressure is not enough). in place or the rollers are out of balance).
Pit off: Refers to the poor adhesion of each layer of paper on the cardboard. There are three methods of checking out the pit:
(1) Make one side of the length of the cardboard close to the ground at an angle of 60°, and push it on the paper with the palm of your hand;
(2) Hold the two sides of the cardboard width and squeeze it to the middle with an appropriate force;
(3) Peeling method, if the paper fibers at the bonded place are not damaged, it means that the paper is not bonded well. The reasons for the pitting may be small amount of glue , foreign matter blocking the paste pipeline, improper adjustment of the slurry level, low paste viscosity, unsuitable heating time and temperature; large difference in cardboard expansion and contraction ratio (such as surface, bottom, see Pit); face paper, bottom paper, see pit paper under pressure improperly.
Blistering: generally appear on the face paper or bottom paper, the reasons are as follows:
(1) The base paper contains a lot of moisture
(2) The quality is poor (uneven thickness, more impurities);
(3) The amount of glue sizing does not meet the requirements (too little glue on the head machine, throwing the pit after blowing or too much glue on the head machine , short time for ventilation and heat dissipation, and too little time for water to evaporate);
(4) The water in the paste evaporates slowly, forming an empty film in the cardboard;
(5) Improper temperature control, mainly Hot Plate;
(6) The pressure is improper, such as the paste wheel is not pressed in place.
Oil stains and spots: There must be no oil stains on the inside and outside of the cardboard, and no spots on the surface paper (except C paper).
Damage: The middle of the cardboard cannot be damaged, and the edge of the cardboard is damaged so as not to affect the appearance.
Wrinkle: refers to the obvious wrinkles on the top paper or bottom paper of the cardboard, which are caused by the following aspects:
(1) Wrinkled base paper;
(2) The paper surface was not stretched and leveled during production;
(3) The tension controller does not control the tension of the surface paper and the bottom paper:
(4) The tension of the surface paper and the bottom paper is not coordinated.
Bending: Curvature refers to the percentage of the highest height between the horizontal planes after the cardboard is bent and the length of the cardboard in the bending direction. It is divided into transverse bending (pit pattern direction) and longitudinal bending (cardboard length direction). Generally, there are more transverse bending . The reasons are as follows:
(1) Moisture (the water content of each layer of raw materials that make up the cardboard or the water content in the paste and the amount of sizing);
(2) Tension : ① machine traction, ② control the stock of pit paper on the bridge (generally its length should be controlled within 1/3 of the total length of the bridge);
(3) Tension adjustment of the controller on the surface, bottom and bracket;
(4) The thermal expansion and contraction of base paper is out of balance with the thermal expansion and contraction ratio of each layer of paperboard
(5) Preheater, heating roller, etc.
Hardness: The hardness of the cardboard is mainly determined by the hardness of the base paper of each layer of the cardboard (especially the hardness of the pit paper). It is affected by the pit machine and flute type.
Color difference: refers to the obvious color difference between the top paper or bottom paper of the same type of cardboard.