On the whole, cardboard distortion is not a single issue. Preventing this from happening can be accomplished by simultaneously removing the warpage (imbalance of moisture content and web tension) of the cardboard in the direction of the corrugations and parallel to the machine. Cardboard warping is usually caused by uneven web tension in the direction of the corrugations, usually occurring at the bond of the double-sided backing paper. This uneven web tension may be caused by the condition of the roll (damaged and inconsistent in shape), unregistered webs of the original paper rack and downstream equipment, or different degrees of rubbing in the direction of the corrugations above the hot plate. In addition, faults on the belts of corrugated board production lines, especially on split belts, may also be the cause of cardboard distortion.
The real cause of cardboard warping in a broad sense, the warpage of the board is caused by the non-uniform variation of the size of the components on the corrugated board, especially the core paper, which usually occurs when the corrugated tip and the bottom paper are firmly bonded and in both No relative movement (sliding) occurs afterwards. Machine-direction (MD) board warpage is caused by the unbalanced change of the upper and lower paper in the rolling direction of the machine due to the various forces of the machine's rolling direction that were originally unbalanced and the unbalanced cyclic changes. End S-board warpage). The main force here is the web tension.
If the tension of the upper sheet is higher than the tension of the lower sheet, the warping of the end-to-end upturned cardboard is caused. This kind of warpage occurs because the upper sheet has a higher degree of stretch than the lower sheet after the sheet is bonded. Therefore, the elasticity of the cardboard back is greater and the tension is released when the cardboard is cut. Conversely, if the tension of the underlying paper is higher than the tension of the paper on the upper sheet, the end-to-end undercut cardboard warps. As a result, end-to-end warpage of the S-board can occur if large amounts of tension occur on the paper or both sides of the paperboard on either side. Cardboard warpage in the corrugated direction is mainly caused by non-uniform variations in the corrugation direction of the upper and lower sheets produced by the original unbalanced forces in the parallel direction of the corrugations. The main force here is due to the change in moisture content, the shrinkage force and expansion force caused by the so-called “wet-up†nature of the base paper. This wet-up behavior is much larger in the corrugation direction than in the machine direction. This shows that the most serious problem we encountered was the warpage of the cardboard in the direction of the corrugations, and also how inconvenient the wet and mottled lines were in the base paper. Therefore, most carton companies do most of their work on cardboard warpage in the direction of corrugation, that is, the research and control of corrugated cardboard warpage.
Roughly speaking, a 1% change in the moisture content of the base paper will change the size of the corrugated cardboard by 0.06% to 0.10%. Because during the board through the corrugated cardboard production line, the moisture content can be changed by 15% to 20%, which may cause the cardboard to have a relative change of 0.9%~2%. On an 80-inch (2.03m) wide cardboard, this value is 0.72 inches to 1.6 inches (18mm to 41mm). This large size change has a great effect on the warpage of the cardboard. Therefore, careful control of the moisture content of the base paper is crucial for the production of flat cardboard.
The change in temperature also causes a change in the size of the board. However, its effect is relatively minimal for cardboard warpage. It is difficult to treat the temperature factor in isolation because changes in temperature are usually accompanied by, or actually cause, changes in the moisture content of the base paper. It is credible to explain the cause of cardboard warpage in the direction of the corrugations by the changes and differences in water content occurring during the manufacture of cardboard.
Cardboard warpage problem solution As we all know, carton warping is the most important obstacle for all carton factories, it will bring a variety of production defects, such as speed reduction and glue, energy bills and many other issues. And it will affect the operation of the box department, such as die cutting difficulties, poor printing and so on. Waste paper also increased, making work more annoying and less smooth.
The main cause of warpage in corrugated board is the uneven water content of the upper and lower paper. There is too much water in the single-sided paper to bend upwards, and too much water in the double-sided paper to bend downwards. To produce flat, strong cardboard, it is important to control the moisture content and sizing method of the two papers.
INTERFlC's pressure bar and hot bar help control these two important factors. To produce straight and strong cardboard, the speed of single-sided and double-sided machines must be kept in sync. Some studies have found that low speed does not cause warp in the board. As long as the single-sided machine and the double-sided machine are kept in sync, there will be no problem.
So how do you produce straight corrugated cardboard? The answer is that there must be a third opposing force that counteracts the two face forces. This counter force arises from the fact that the top and roots of the corrugations at the double-sided bond are very moist, and the water content of the double-sided backing paper and the adhesive itself is due to the adhesiveness of the double-sided tissue on the top and roots of the corrugations. When the top and root of the corrugated fiber shrink to lose moisture in order to conform to the surrounding air, the force generated will try to warp the formed cardboard backsheet. Therefore, in order to produce a straight corrugated cardboard, this counter force must be able to accurately balance out the force generated by the aforementioned two facing papers in the paperboard forming process. The shrinkage of the corrugated tip not only affects the loss of the size of the cardboard caused by the loss of moisture content, but also reflects the fact that the paper is wetted and then dried and shrunk, ultimately resulting in the size of the cardboard being smaller than the original size.
Coated with the following conditions, can be made of flat corrugated board (ie 24 inches wide cardboard, deviation of 0.25 inches or 600mm wide cardboard, deviation 6mm)
·Management promised to be processed into flat cardboard:
· The uniformity of the water content of the base paper is within the specified range:
The corrugated cardboard production line is in a good mechanical condition, with some kind of cardboard warpage control tool:
· The operating procedures of the corrugated board production line have been improved and the staff has been fully trained in the board warpage control method: in order to produce straight paper boards at all times, the above four conditions must be met.
In addition, we can also give an example of a system solution. This example system scenario includes (in order of importance):
· Installation speed CODEC SpeedChartRecorder-SCR;
· Install COPAR flyover speed control (BSC) to enable single-sided and double-sided machines to automatically synchronize at the same speed, while maintaining the minimum and stable paper volume on the overpass;
· Poorly installed splicer (especially double sided);
Install the motor (motor) so that the preheat can be rotated;
• Installation of COPAR Double Sided Machine Speed ​​Control (DBSC) enables the double sided machine to shorten the acceleration or deceleration time, and maintain the fastest speed when producing various varieties;
· Install FRIESE corrugating rollers (reducing the amount of glue thus also reducing the chance of warpage);
·Install INTERFIC ContactBars;
· Install EQUALINER2000 tension balancer (on double sided preheater);
· The installed bridge brake (brake) makes the single-sided cardboard bridge balance less vibration and less impact;
· The installation of INTERFIC ThermlBars is the perfect bending control system;
· Install RINC top paper holder paper tube clamps;
· The well-installed pneumatic brake is placed on the paper holder.
· Install COPARSWS segmented spray system;
• Install INTERFIC Traction Bars.
After using such an example solution, the actual effect was to increase the total average speed of the carton production line by 12.6%, and increase the thickness of the cardboard by 28.5%. The cardboard's adhesive strength, edge pressure and carton pressure strength increase accordingly. The employee’s daily expenses were reduced by 4,000 US dollars a year, the plane source cost was 15,000 US dollars a year, and the glue consumption was also reduced by 21,000 US dollars. With THERMO BARS, the warp of the cardboard can be easily controlled by simply touching it with your finger on the computer.
Specific measures to adjust the curling of corrugated board is a common phenomenon in the production process of corrugated board. Take appropriate measures to adjust, so that the problem can be quickly eliminated. Here we put forward some ideas for adjustment:
· Must understand the highest economical operating speed and hot plate normal temperature of the drying tunnel used in the production line.
· The stable and highest economical operating speed should be used to determine the proper temperature for the various layers, inner and core papers in the paperboard production process before compounding, and to control them reliably.
·Because each layer of paper is dried at different temperatures and heat and humidity conditions during the drying tunnel operation, where the tissue paper is directly in contact with the hot plate, it is in the dry environment with the highest temperature, so first control the composite paper before the composite Humidity, to ensure that the face paper has been dried and not too dry and brittle, as a benchmark to adjust the temperature of other cardboard.
· Adjust and control the humidity of other layers of cardboard according to the upturn or downturn phenomenon. In addition to the drying season in Shanghai and other factors that make the moisture content of the paper cylinder less humid, Shanghai printing generally does not need to humidify at most without preheating or reducing the warm-up area.
Do not avoid excessive moisture in the tissue to increase the humidity of other papers for balance. Although this can also improve, but it affects the economic speed of drying, reducing the production efficiency, while the board has not dried after the drying tunnel The part will continue to distribute water and hide the hidden dangers of cardboard deformation.
• As long as the composite requirements can be satisfied, the amount of upper paste should not be too large, which can reduce the cardboard quality problems caused by the deformation of the paperboard composite and reduce the material consumption of the adhesive.
· The old conveyor belt will affect the humidity of the upper board due to poor ventilation. The same day will also cause the upper board to absorb the steam generated by the lower board to generate moisture deformation (blanket shape). The old production line should pay attention to prevent this from being ignored. factor.
• Unbalanced tension in the layers of the paperboard can also cause longitudinal warping of the paperboard. Pay attention to the transport tension of high-speed good paper and paperboard.
Papers produced by different manufacturing equipment and processes and papers from different origins may have different shrinkage direction differences and shrinkage rates; differences in the paper and stacking conditions of different batches will cause the moisture content of the paper to be different. The base papers that were purchased during the dry and wet seasons, or the same base papers, were used in different seasons, and the humidity inside and outside the roll paper was also different.
The five-layer corrugated cardboard is downturned, and the hot plate temperature is measured to 170°C~190°C. Shanghai printing companies can increase the paste and reduce the drying process of A-Watts. During the process, the paperboard can be flattened, but after cooling, it will be upturned. The processing method is:
· The phenomenon of horizontal tilting down of the five-layer corrugated cardboard is due to the fact that the humidity of the tissue prior to recombination is too high. When the cardboards of different levels and humidity are compounded, the mutual position is the bonding between the top and the back of the corrugated medium. Fixed point, into the drying tunnel after the drying, the surface area of ​​the paper surface humidity is too large to generate tension to the heart, so that the whole cardboard down occurs.
The solution should consider increasing the warm-up area of ​​the tissue and reducing the humidity of the tissue prior to compounding. In the case of the highest and stable economic movement speed, the cardboard is down, but the composite quality of other layers of paper and the moisture after drying meet the requirements and can be eliminated by adjusting the humidity of the tissue paper. Otherwise, we must consider the moisture state of the other layers of paper before final compounding. At the same time, we need to reduce the warm-up area of ​​other layers of cardboard. Further measures can also use several layers of cardboard to steam humidify, and then properly increase the speed. Each layer of paper is dried under different temperature, heat dissipation, and humidity conditions during the operation of the drying tunnel. Through adjustment, the humidity of all papers can be adapted to the basic drying conditions under the respective drying environment conditions when the drying path is passed through the drying tunnel. Balance can ensure the flatness of the board after drying.
The practice of increasing the amount of paste and humidity in the corrugated board should be a measure taken when the amount of paste is not enough and the A楞 second-layer paperboard is too dry after the final drying tunnel has come out. One-sided increase in the amount of paste will increase the cost of adhesive consumption and make A dome due to the increase of water and affect the strength, in the composite deformation of the skull type, there is a collapse, dry and then there will be "see-saw" defects. Increased humidity will affect the drying rate of the drying tunnel.
The real cause of cardboard warping in a broad sense, the warpage of the board is caused by the non-uniform variation of the size of the components on the corrugated board, especially the core paper, which usually occurs when the corrugated tip and the bottom paper are firmly bonded and in both No relative movement (sliding) occurs afterwards. Machine-direction (MD) board warpage is caused by the unbalanced change of the upper and lower paper in the rolling direction of the machine due to the various forces of the machine's rolling direction that were originally unbalanced and the unbalanced cyclic changes. End S-board warpage). The main force here is the web tension.
If the tension of the upper sheet is higher than the tension of the lower sheet, the warping of the end-to-end upturned cardboard is caused. This kind of warpage occurs because the upper sheet has a higher degree of stretch than the lower sheet after the sheet is bonded. Therefore, the elasticity of the cardboard back is greater and the tension is released when the cardboard is cut. Conversely, if the tension of the underlying paper is higher than the tension of the paper on the upper sheet, the end-to-end undercut cardboard warps. As a result, end-to-end warpage of the S-board can occur if large amounts of tension occur on the paper or both sides of the paperboard on either side. Cardboard warpage in the corrugated direction is mainly caused by non-uniform variations in the corrugation direction of the upper and lower sheets produced by the original unbalanced forces in the parallel direction of the corrugations. The main force here is due to the change in moisture content, the shrinkage force and expansion force caused by the so-called “wet-up†nature of the base paper. This wet-up behavior is much larger in the corrugation direction than in the machine direction. This shows that the most serious problem we encountered was the warpage of the cardboard in the direction of the corrugations, and also how inconvenient the wet and mottled lines were in the base paper. Therefore, most carton companies do most of their work on cardboard warpage in the direction of corrugation, that is, the research and control of corrugated cardboard warpage.
Roughly speaking, a 1% change in the moisture content of the base paper will change the size of the corrugated cardboard by 0.06% to 0.10%. Because during the board through the corrugated cardboard production line, the moisture content can be changed by 15% to 20%, which may cause the cardboard to have a relative change of 0.9%~2%. On an 80-inch (2.03m) wide cardboard, this value is 0.72 inches to 1.6 inches (18mm to 41mm). This large size change has a great effect on the warpage of the cardboard. Therefore, careful control of the moisture content of the base paper is crucial for the production of flat cardboard.
The change in temperature also causes a change in the size of the board. However, its effect is relatively minimal for cardboard warpage. It is difficult to treat the temperature factor in isolation because changes in temperature are usually accompanied by, or actually cause, changes in the moisture content of the base paper. It is credible to explain the cause of cardboard warpage in the direction of the corrugations by the changes and differences in water content occurring during the manufacture of cardboard.
Cardboard warpage problem solution As we all know, carton warping is the most important obstacle for all carton factories, it will bring a variety of production defects, such as speed reduction and glue, energy bills and many other issues. And it will affect the operation of the box department, such as die cutting difficulties, poor printing and so on. Waste paper also increased, making work more annoying and less smooth.
The main cause of warpage in corrugated board is the uneven water content of the upper and lower paper. There is too much water in the single-sided paper to bend upwards, and too much water in the double-sided paper to bend downwards. To produce flat, strong cardboard, it is important to control the moisture content and sizing method of the two papers.
INTERFlC's pressure bar and hot bar help control these two important factors. To produce straight and strong cardboard, the speed of single-sided and double-sided machines must be kept in sync. Some studies have found that low speed does not cause warp in the board. As long as the single-sided machine and the double-sided machine are kept in sync, there will be no problem.
So how do you produce straight corrugated cardboard? The answer is that there must be a third opposing force that counteracts the two face forces. This counter force arises from the fact that the top and roots of the corrugations at the double-sided bond are very moist, and the water content of the double-sided backing paper and the adhesive itself is due to the adhesiveness of the double-sided tissue on the top and roots of the corrugations. When the top and root of the corrugated fiber shrink to lose moisture in order to conform to the surrounding air, the force generated will try to warp the formed cardboard backsheet. Therefore, in order to produce a straight corrugated cardboard, this counter force must be able to accurately balance out the force generated by the aforementioned two facing papers in the paperboard forming process. The shrinkage of the corrugated tip not only affects the loss of the size of the cardboard caused by the loss of moisture content, but also reflects the fact that the paper is wetted and then dried and shrunk, ultimately resulting in the size of the cardboard being smaller than the original size.
Coated with the following conditions, can be made of flat corrugated board (ie 24 inches wide cardboard, deviation of 0.25 inches or 600mm wide cardboard, deviation 6mm)
·Management promised to be processed into flat cardboard:
· The uniformity of the water content of the base paper is within the specified range:
The corrugated cardboard production line is in a good mechanical condition, with some kind of cardboard warpage control tool:
· The operating procedures of the corrugated board production line have been improved and the staff has been fully trained in the board warpage control method: in order to produce straight paper boards at all times, the above four conditions must be met.
In addition, we can also give an example of a system solution. This example system scenario includes (in order of importance):
· Installation speed CODEC SpeedChartRecorder-SCR;
· Install COPAR flyover speed control (BSC) to enable single-sided and double-sided machines to automatically synchronize at the same speed, while maintaining the minimum and stable paper volume on the overpass;
· Poorly installed splicer (especially double sided);
Install the motor (motor) so that the preheat can be rotated;
• Installation of COPAR Double Sided Machine Speed ​​Control (DBSC) enables the double sided machine to shorten the acceleration or deceleration time, and maintain the fastest speed when producing various varieties;
· Install FRIESE corrugating rollers (reducing the amount of glue thus also reducing the chance of warpage);
·Install INTERFIC ContactBars;
· Install EQUALINER2000 tension balancer (on double sided preheater);
· The installed bridge brake (brake) makes the single-sided cardboard bridge balance less vibration and less impact;
· The installation of INTERFIC ThermlBars is the perfect bending control system;
· Install RINC top paper holder paper tube clamps;
· The well-installed pneumatic brake is placed on the paper holder.
· Install COPARSWS segmented spray system;
• Install INTERFIC Traction Bars.
After using such an example solution, the actual effect was to increase the total average speed of the carton production line by 12.6%, and increase the thickness of the cardboard by 28.5%. The cardboard's adhesive strength, edge pressure and carton pressure strength increase accordingly. The employee’s daily expenses were reduced by 4,000 US dollars a year, the plane source cost was 15,000 US dollars a year, and the glue consumption was also reduced by 21,000 US dollars. With THERMO BARS, the warp of the cardboard can be easily controlled by simply touching it with your finger on the computer.
Specific measures to adjust the curling of corrugated board is a common phenomenon in the production process of corrugated board. Take appropriate measures to adjust, so that the problem can be quickly eliminated. Here we put forward some ideas for adjustment:
· Must understand the highest economical operating speed and hot plate normal temperature of the drying tunnel used in the production line.
· The stable and highest economical operating speed should be used to determine the proper temperature for the various layers, inner and core papers in the paperboard production process before compounding, and to control them reliably.
·Because each layer of paper is dried at different temperatures and heat and humidity conditions during the drying tunnel operation, where the tissue paper is directly in contact with the hot plate, it is in the dry environment with the highest temperature, so first control the composite paper before the composite Humidity, to ensure that the face paper has been dried and not too dry and brittle, as a benchmark to adjust the temperature of other cardboard.
· Adjust and control the humidity of other layers of cardboard according to the upturn or downturn phenomenon. In addition to the drying season in Shanghai and other factors that make the moisture content of the paper cylinder less humid, Shanghai printing generally does not need to humidify at most without preheating or reducing the warm-up area.
Do not avoid excessive moisture in the tissue to increase the humidity of other papers for balance. Although this can also improve, but it affects the economic speed of drying, reducing the production efficiency, while the board has not dried after the drying tunnel The part will continue to distribute water and hide the hidden dangers of cardboard deformation.
• As long as the composite requirements can be satisfied, the amount of upper paste should not be too large, which can reduce the cardboard quality problems caused by the deformation of the paperboard composite and reduce the material consumption of the adhesive.
· The old conveyor belt will affect the humidity of the upper board due to poor ventilation. The same day will also cause the upper board to absorb the steam generated by the lower board to generate moisture deformation (blanket shape). The old production line should pay attention to prevent this from being ignored. factor.
• Unbalanced tension in the layers of the paperboard can also cause longitudinal warping of the paperboard. Pay attention to the transport tension of high-speed good paper and paperboard.
Papers produced by different manufacturing equipment and processes and papers from different origins may have different shrinkage direction differences and shrinkage rates; differences in the paper and stacking conditions of different batches will cause the moisture content of the paper to be different. The base papers that were purchased during the dry and wet seasons, or the same base papers, were used in different seasons, and the humidity inside and outside the roll paper was also different.
The five-layer corrugated cardboard is downturned, and the hot plate temperature is measured to 170°C~190°C. Shanghai printing companies can increase the paste and reduce the drying process of A-Watts. During the process, the paperboard can be flattened, but after cooling, it will be upturned. The processing method is:
· The phenomenon of horizontal tilting down of the five-layer corrugated cardboard is due to the fact that the humidity of the tissue prior to recombination is too high. When the cardboards of different levels and humidity are compounded, the mutual position is the bonding between the top and the back of the corrugated medium. Fixed point, into the drying tunnel after the drying, the surface area of ​​the paper surface humidity is too large to generate tension to the heart, so that the whole cardboard down occurs.
The solution should consider increasing the warm-up area of ​​the tissue and reducing the humidity of the tissue prior to compounding. In the case of the highest and stable economic movement speed, the cardboard is down, but the composite quality of other layers of paper and the moisture after drying meet the requirements and can be eliminated by adjusting the humidity of the tissue paper. Otherwise, we must consider the moisture state of the other layers of paper before final compounding. At the same time, we need to reduce the warm-up area of ​​other layers of cardboard. Further measures can also use several layers of cardboard to steam humidify, and then properly increase the speed. Each layer of paper is dried under different temperature, heat dissipation, and humidity conditions during the operation of the drying tunnel. Through adjustment, the humidity of all papers can be adapted to the basic drying conditions under the respective drying environment conditions when the drying path is passed through the drying tunnel. Balance can ensure the flatness of the board after drying.
The practice of increasing the amount of paste and humidity in the corrugated board should be a measure taken when the amount of paste is not enough and the A楞 second-layer paperboard is too dry after the final drying tunnel has come out. One-sided increase in the amount of paste will increase the cost of adhesive consumption and make A dome due to the increase of water and affect the strength, in the composite deformation of the skull type, there is a collapse, dry and then there will be "see-saw" defects. Increased humidity will affect the drying rate of the drying tunnel.
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