In general, corrugated cardboard warping deformation has six phenomena, the most common are:
1. Horizontal warping
causes: the moisture content of the base paper is too high (or the moisture content of the face paper is low); Single side corrugated bonding moisture too much; The quantitative grade of inner and facial paper is too unequal.
Solution: (1) Increase the winding surface of lining paper on the tumble dryer of single-sided machine; (2) Reduce the winding surface of the inner paper on the double layer preheater; (3) Close part of the steam valve of the flat dryer; (4) Improve the running speed of the composite machine; (5) Reduce the gap between the scraping roller, the sizing roller and the lower corrugating roller, and reduce the sizing amount of single-side corrugating; (6) Replace the paper seriously beyond the moisture requirements. 2. Transverse warping
causes: the moisture content of face paper base paper is too high; The temperature and velocity at the heating site are abnormal.
Solution: (1) Increase the heating winding surface of the face paper on the double layer preheater; (2) The use of good viscosity adhesive, reduce the amount of glue compounding machine; (3) Reduce the winding surface of the paper in the single-side machine on the roller dryer; (4) Reduce the production speed at the compound machine; (5) Correctly adjust the speed of the production line and the steam valve of the flat dryer to match; (6) Replace the face paper that seriously exceeds the moisture requirements.
The so-called cardboard false adhesion refers to the paper, paper and corrugated paper behind the machine can be peeled off at will.
The main reasons are: (1) the adhesive viscosity is not enough or has deteriorated; (2) Corrugating machine or composite locomotive speed is too fast; (3) Corrugation machine pressure roll is uneven or corrugation roll has been worn; (4) The gap between the cots of the composite gluing machine is too large; (5) the moisture content of paper is too high. Solutions: (1) Improve and stabilize the quality of adhesives. Relevant data suggest that the viscosity of adhesives is generally 60S to 90S in winter; Summer is usually 90S to 120S. The viscosity of the seven-layer box is generally about 305 slower than that of the three-layer box; (2) Ensure that the steam pressure is 1.0MPa to 1.2MPa, and the temperature of each roll and flat dryer is about 160℃; (3) The domestic corrugated roller must be replaced in time when the output reaches 3 million long meters to 3.5 million long meters.
The so-called washboard phenomenon refers to the concave phenomenon between the corrugated board and the back of the corrugated peak on the surface paper, the shape of which is similar to that of the household washboard, so it is called the washboard phenomenon.
The root cause of the phenomenon of corrugated cardboard washboard is mainly attributed to the improper glue on the adhesive, caused by the influence of excessive glue gathered on both sides of the corrugated peak. This situation for low quantitative box board paper especially prominent harm.
The specific methods to control the phenomenon of cardboard washboard are: adjust the quantity of face paper, use the box board paper with a higher quantity is the most direct and effective way to eliminate and reduce the shape of the washboard (but will increase the cost); Using high quality adhesive can reduce the sizing amount of Lengfeng; Control the heating and winding surface of the face paper on the pre-heater, because the box board paper is too dry to absorb more glue, easy to produce the phenomenon of rubbing board; Adjust the parallelism of the compound glue machine and the paper guide roller and the gap between them, strictly the pressure of the guide roller (press roll), to prevent the increase of the amount of glue after collapsing.
In the process of producing corrugated cardboard, the water content control of cardboard is very important, when the water is too high, the processed cardboard will appear soft, not flat, easy to collapse after the box. When the water is low, the cardboard processed is hard, brittle and easy to burst after the box. The control of cardboard moisture is a complicated thing, it is mainly determined by the following two factors:
The moisture of the base paper into the factory should be strictly controlled, according to the current standard: the moisture of the base paper delivery state should be (8±2) %. The storage of base paper is best to set up a separate warehouse, the temperature is generally (18±3) ℃, the humidity is generally (35±5) %. Do not put in the open air, otherwise easy to cause moisture changes and both ends are different from the middle.
Temperature is one of the determining factors affecting the quality of corrugated board. It can not only adjust the moisture of the base paper, but also make the base paper temperature, is an important condition for curing paste. Therefore, many preheaters and flat dryer are set in the cardboard production line to adjust the moisture content of base paper and single-sided paper, and make the paste solidify and finally achieve the purpose of bonding.
In order to effectively control the moisture of finished corrugated cardboard, we must pay attention to the following matters:
If the moisture of the cardboard is too high, the temperature of the preheating roll can not meet the requirements, it is necessary to increase the steam pressure of the boiler, so that the steam supplied can reach the saturated steam. Under normal circumstances, the steam pressure should be maintained at 1.1Mpa±0.2Mpa.
If the moisture is low, it is necessary to adjust the guide roller, reduce the preheating area, and make full use of the single-side machine spray device (wet roller), spray the base paper, increase the moisture of the base paper, so that it can meet the standard requirements.
When the flat dryer is working, it should not be stopped until it is absolutely necessary. Single-sided machine should speed up before replacing the base paper, accumulate more paper on the bridge; After receiving the signal, the speed of the composite machine should be reduced, and the speed should be increased after the completion of the single-sided machine receiving paper. In case of equipment failure and need to stop, lift the conveyance blanket to prevent excessive loss of water on the board of the flat dryer.
For single-sided machine, to adjust the gap between the rubber roller and the scraping roller. Under normal circumstances, the gap between the upper rubber roller and the scraping rubber roller is 0.2mm to 0.25mm, and the gap between the rubber coating roller and the main corrugated roller should be 0.02mm larger than the thickness of the corrugated paper used in the heat engine state. For the double-sided machine, the gap between the scraping roller and the upper roller is 0.2mm to 0.25mm, the gap between the press roller and the upper roller should be 0.05mm to 0.1mm smaller than the height of the single-sided corrugated cardboard through, and the gap between the two rollers should be consistent, which can be measured with a feeler.