Causes and solutions of bending and warping of corrugated board

On the whole, cardboard distortion is not a single issue To prevent this phenomenon, the warpage (water content imbalance and web tension) of the paperboard in the corrugating direction and in the parallel direction with the machine can be eliminated at the same time Paper board twist is usually caused by uneven web tension in the direction of corrugating (usually occurs at the bonding of double-sided backing paper) This uneven web tension may be caused by the roller state (damaged and inconsistent shape), the web of the base paper frame and downstream equipment is not aligned, or the different degree of friction in the corrugated direction on the hot plate In addition, the failure of the corrugated board production line belt, especially the split belt, may also be the cause of the cardboard distortion The real cause of the warpage of the paperboard In a broad sense, the warpage of the paperboard is caused by the uneven change of the size of the combined parts on the corrugated paperboard, especially the core paper, which usually occurs after the corrugated tip and the bottom paper are firmly adhered and no relative movement (sliding) occurs between them Machine direction (MD) board warping is caused by the uneven change of the upper and lower paper in the rolling direction of the machine caused by the original imbalance of various forces in the rolling direction of the machine and the periodic change of this imbalance (end-to-end S-shaped board warping) The main force here is web tension If the tension of the upper surface paper is higher than that of the lower bottom paper, it will cause the end-to-end up warped cardboard This warping occurs because after the cardboard is bonded, the upper surface paper has a higher degree of extension than the lower bottom paper As a result, the elastic force on the back of the paperboard is greater, and the tension can be released after the paperboard is cut On the contrary, if the tension of the bottom paper is higher than that of the top paper, the end-to-end down bending paperboard will be warped Therefore, if the tension of any side or both sides of the board fluctuates on a large scale, end-to-end S-shaped board warpage will occur The warpage of corrugated board is mainly caused by the uneven change of the upper and lower paper in the corrugated direction caused by the original unbalanced force in the corrugated parallel direction The main force here is caused by the change of moisture content, that is, the shrinkage force and expansion tension caused by the so-called "wet expansion" characteristics of the base paper This kind of wetness is much greater in the direction of corrugation than in the direction of machine, which shows that the serious problem we encounter in Zui is the warpage of the cardboard in the direction of corrugation, and also shows how much trouble the wetness in the base paper is Therefore, most of the work done by many carton enterprises is about the research and control of the warpage of corrugated board Roughly speaking, every 1% change of the moisture content of the base paper will change the size of the corrugated direction board by 0.06% - 0.10% Because the change of water content can be up to 15% - 20% during the process of cardboard passing through the corrugated cardboard production line, it may cause the relative change of 0.9% - 2% size of cardboard On a piece of 80 inch (2.03m) wide cardboard, the value is 0.72 inch to 1.6 inch (18mm to 41mm) Such a large size change has a great influence on the warpage of paperboard Therefore, careful control of the moisture content of the base paper is very important for the production of the straight cardboard The change of temperature also causes the change of size of cardboard However, its effect on the warpage of paperboard is relatively small It is difficult to treat the factor of temperature in isolation, because the change of temperature usually accompanies, or actually causes, the change of moisture content in the base paper It is reliable to explain the cause of the warpage of the paperboard in the direction of corrugation by the change and difference of the moisture content in the process of making the paperboard As we all know, the bending and warping of cardboard is the main obstacle of Zui in all carton factories, which will bring various production defects, such as the decrease of speed, the increase of glue paste, the increase of energy expenditure and so on And it will affect the operation of the box making part, such as die cutting difficulties, printing problems and so on As a result, waste paper also increased, making the work more troublesome and less smooth The main reason of corrugated board warping is the water content imbalance between the upper and lower paper Up bending is too much water on one side of the paper, down bending is too much water on both sides of the paper In order to produce straight and hard board, we must control the moisture content and gluing method of these two paper Interflc's touch bar and hot bar can help control these two important factors If you want to produce straight and strong cardboard, the speed of single side machine and double side machine must keep in step It has been found that low speed does not cause bending and warping of paperboard, as long as the single-sided machine and double-sided machine keep synchronized, there will be no problem So how to produce straight corrugated board? The answer is that there must be a third counter force that counteracts these two forces This reverse force is generated when the top and root of the corrugated at the double-sided bonding place are very wet Because the double-sided surface paper at the top and root of the corrugated is coated with adhesive, and the water content of the double-sided bottom paper and the adhesive itself is added, when the top and root of the corrugated lose water and contract in order to be consistent with the surrounding air trend, the generated force will try to make the reverse cardboard warped after forming Qu Therefore, in order to produce a straight corrugated board, the reverse force must be able to accurately balance the force generated by the two aforementioned face papers in the board forming process The shrinkage of the corrugated tip not only affects the size loss of the paperboard caused by the loss of moisture content, but also reflects that the paper is wetted and then dried Zui eventually makes the size of the paperboard smaller than the original size Under the following circumstances, the straight corrugated board can be made (that is, 24 inch wide board with a deviation of 0.25 inch or 600mm wide board with a deviation of 6mm) · the management promised to process the straight board: · the uniformity of the moisture content of the base paper is within the specified range:· Corrugated board production line is in a good mechanical state, with some kind of paper board warping control tools attached: · the operation procedure of corrugated board production line has been improved, and the staff has been fully trained in the paper board warping control method: in order to always produce straight paper board, the above four conditions must be met In addition, we can give an example of a system solution This example system scheme includes (in order of importance): · installation of coparspeedchartrecorder SCR; · installation of copar bridge speed control (BSC) to automatically synchronize the single side machine and the double side machine at the same speed, while maintaining a small and stable amount of paper on the bridge· The paper feeder (especially the double-sided part) with poor installation; · the motor (motor) is installed to make the preheating lack rotate; · the copar double-sided machine speed control (DBSC) is installed to shorten the acceleration or deceleration time of the double-sided machine, and the Zui speed can be maintained in the production of various varieties; · the Friese corrugated roller is installed（ Reduce the amount of glue and thus reduce the chance of warping); · install the interfic single pressure bar (contact bars); · install the equiliner2000 tension balancer (on the double-sided preheater); · install the overpass brake (brake) to balance the single-sided cardboard across the bridge with less vibration and less impact; · install the interfic The hot bending bar (ThermlBars) is a perfect curling control system; install RINC base paper holder pipe clamp; install a good pneumatic brake on the original paper rack, install the COPARSWS segmented spray system; install the INTERFIC traction rod (TractionBars) After using such a set of example solutions, the actual effect is that the total average speed of the carton production line is increased by 12.6%, and the running cardboard is increased by 28.5% The adhesive strength, side pressure beat and carton pressure strength of the paperboard are increased correspondingly The cost of exceeding the daily size of employees is reduced by US $4000 a year, the cost of planning sources is saved by US $15000 a year, and the glue consumption is also reduced by US $21000 With thermobars, the bending and warping of cardboard can be easily controlled by touching the computer with fingers Specific measures to adjust the bending and warping of corrugated board The bending and warping of corrugated board is a common phenomenon in the production process of corrugated board Appropriate measures should be taken to adjust it so that the problem can be eliminated quickly Some ideas for adjustment are put forward here for reference: · it is necessary to understand the stable Zui high economic operation speed and normal temperature of hot plate of the used production line, · the proper temperature of each layer, inner and core paper before lamination should be determined and reliably controlled with stable Zui high economic operation speed · as each layer of paper is dried in different temperature and heat dissipation wet environment during the drying process, in which the surface paper directly contacts the hot plate and is in a high temperature Zui drying environment, first control the surface paper humidity before compounding to ensure that the surface paper has been dried and can not be too dry and brittle, as a reference for adjusting the temperature of other cardboard · adjust and control the humidity of other layers of cardboard according to the phenomenon of up warping or down warping In addition to the dry season in this area or other factors that make the humidity of the paper cylinder too small, generally speaking, it is not necessary to humidify Zui to not preheat or reduce the preheat area · do not increase the humidity of other papers for balance due to the high humidity of the paper Although this can be improved, it will affect the economic speed of drying and reduce the production efficiency At the same time, the part of the paper board that has not been dried after the drying path will continue to emit water, and the hidden danger of the paper board that is buried will continue to deform · as long as the composite requirements can be met, the amount of paste should be small rather than large, which not only reduces the quality problems caused by the composite daily size deformation of the paperboard, but also reduces the material consumption of the adhesive · the old conveyor belt will affect the moisture volatilization of the upper cardboard due to poor air permeability, and the upper cardboard will absorb the steam emitted by the lower cardboard to produce moisture absorption deformation (washboard shape) The old production line should pay attention to prevent ignoring this factor · the unbalanced tension of each layer of cardboard will also cause the cardboard to warp longitudinally Pay attention to the high-speed and good conveying tension of the face paper and each layer of cardboard Paper produced by different manufacturing equipment and processes and paper from different places of origin will have different shrinkage direction and shrinkage rate; different batches of paper and different stacking conditions will cause different moisture content of paper The humidity of the inner and outer layers of the same roll of paper will be different when the base paper purchased in dry season and wet season, or when the same base paper is used in different seasons The five layer corrugated board is warped down, and the hot plate temperature is measured to be 170 ℃ ~ 190 ℃ For example, if a tile is used to increase paste quantity and reduce drying, the paperboard can be flattened in the process, but it can be turned up after cooling The treatment method is as follows: · the phenomenon of five-layer corrugated paperboard turning down horizontally is due to the high humidity of the face paper before laminating Once the paperboards with different humidity of each layer are laminating, the positions of each other