1. Overview Warpage of corrugated board is a very common and troublesome phenomenon in the production process of corrugated board. For example, we can see that at some paperboard mills' cardboard output lines, it is necessary to manually reverse the stacked paperboards. On the one hand, the labor intensity of workers is very high, and on the other hand the speed of the production line is affected. In the latter equipment, for example, in the paper feeding operation of the fully automatic printing slot machine, we often see that in order to make the paper feed smoothly, the worker presses the paper board down firmly before the paper feeding table. In fact, the warpage of cardboard will bring many unfavorable factors to the enterprise, such as the increased labor intensity of workers, the increase of rejection rate, the inability to use automated machines normally, and the impact on productivity. In order to make everybody attach importance to this issue as much as possible and draw lessons from the experience of foreign companies in this area, it is very necessary to draw a solution.
Second, the definition of warpage At present, there is no clear definition of cardboard warping in the United States, in the United States CID (CORRUGATEDINDUSTRYDEVELOPMENT) put forward the number of ketones expressed warpage (WARP), and to illustrate the actual use of warping corrugated board in the use of the allowable degree . If a warp of 1/4 inch (approximately 6 mm) in width 24 in (approximately 600 mm as a unit) is defined as warpage equal to 1/4 (FIG. 1), this number is used as the allowable limit of warpage. At the same time, the formula (1) is defined. From the formula, we have obtained that the paper board warping factor of the 1/4 warpage of the 24 in width board is also 1/4. Then, with respect to wide paper sheets, the warpage of a unit of 24 inches wide is expressed as a formula that is inversely proportional to the unit square, that is:
Warpage = Warp coefficient × (unit squared) 2
(WARP)=WARPFACTOR×(UNIT)2
For example, the permissible value of the warp degree of a paper sheet having a 1/4 WF in 48 inches wide in the United States is 1 mm in the above formula.
The allowable value of warpage in Japan is the same as that in the United States. For example, the allowable warpage limit is 9/6in (14.1mm) for a width of 36in, and the allowable warpage limit is 1in (25.4mm) for 48in (1200mm).
Third, warping types Corrugated board warping types can be cited as follows:
(1) Longitudinal warpage (2) Lateral warpage Tensile warpage such as warping of warp in the longitudinal and transverse directions. Lateral warping is divided into upward warping and downward S warping.
Fourth, the main cause of warping The cause of warping is very complex, summed up is due to the fact that noodle paper (ie, corrugated paper, paper and paper) in the production due to a variety of reasons caused by their expansion and contraction differences.
The cause of warping is:
1 The nature and type of paper;
2 Moisture, heat, and tension The nature and type of paper.
1, the nature and type of paper:
In terms of the nature of the paper, the paper absorbs water and swells, drying shrinks. The wet paper has the property of absorbing large water. The size of the change in size is more than twice as large in the horizontal direction than in the vertical direction.
The type of paper, such as the degree of stretching of kraft paper and tea board paper, varies depending on the composition of the fibers and the manufacturing method. The same kind of paper may be of different grades, and warpage tends to occur when the two grades of corrugated paperboards with great differences are registered in the A-level and the C-level.
2, moisture, heat, tension in the corrugated board processing process, single-sided corrugating machine and the paste machine at the glue, the glue contains a lot of water, and then heated to dry, this situation the impact of warpage Great. It also causes uneven gluing on machinery and operation, resulting in inconsistent moisture in the cardboard. Japan’s survey of 16 plants showed that the amount of single-sided corrugators is at least 2.4 g/m2, a maximum of 8.79 g/m2, and the amount of paper machine attachment is at least 2.8 g/m2. 18.6 g/m2. In addition, with respect to the horizontal attachment fluctuations of corrugated cardboard, the survey results also confirmed that the single-faced corrugating machine is 0.5-3.5 g/m2, and the paper-bonding machine is 0.5-14.7 g/m2. Explain the uneven moisture content.
With respect to the heating problem, when a double-sided machine is used, single-faced corrugations absorb moisture and heat at the single-face corrugating machine, and also absorb water from the glue on the paste-gluer machine. Therefore, the single-faced corrugated cardboard tends to be horizontally stretched. On the other hand, paperboards that are in direct contact with the flatbed dryer on a double sided machine tend to shrink when dried.
In the process of production of corrugated cardboard, the tension of the paper from the paper-feeding frame to the double-machine is inconsistent. This inconsistency contributes to the inconsistency of lateral shrinkage of the paperboard.
Fifth, the main causes of various warpage and countermeasures 1, upward warpage, downward warpage As mentioned earlier, single-sided corrugated cardboard in a single-faced corrugating machine and paste and paste at the office, horizontal elongation, and Noodle paper (face paper) is in an over-dried state due to direct contact with the preheater and the double-sided plate dryer, and is fed into the corrugated cardboard after entering the cooling section of the double-sided machine. The corrugated cardboard is exposed to the air. In order to achieve moisture balance, moisture is released from the side of the single-faced corrugated sheet with a large moisture content, and at the same time shrinkage occurs; while the dried noodle sheet absorbs moisture and elongates, a warp phenomenon occurs. If the above situation is reversed (actually, the bonding speed is too high as compared with the drying capability of the flat-plate dryer), the warping occurs. (Zheng Zhengpei, Carton Machinery Branch of Shanghai Electric Group Printing & Packaging Co., Ltd.)
Second, the definition of warpage At present, there is no clear definition of cardboard warping in the United States, in the United States CID (CORRUGATEDINDUSTRYDEVELOPMENT) put forward the number of ketones expressed warpage (WARP), and to illustrate the actual use of warping corrugated board in the use of the allowable degree . If a warp of 1/4 inch (approximately 6 mm) in width 24 in (approximately 600 mm as a unit) is defined as warpage equal to 1/4 (FIG. 1), this number is used as the allowable limit of warpage. At the same time, the formula (1) is defined. From the formula, we have obtained that the paper board warping factor of the 1/4 warpage of the 24 in width board is also 1/4. Then, with respect to wide paper sheets, the warpage of a unit of 24 inches wide is expressed as a formula that is inversely proportional to the unit square, that is:
Warpage = Warp coefficient × (unit squared) 2
(WARP)=WARPFACTOR×(UNIT)2
For example, the permissible value of the warp degree of a paper sheet having a 1/4 WF in 48 inches wide in the United States is 1 mm in the above formula.
The allowable value of warpage in Japan is the same as that in the United States. For example, the allowable warpage limit is 9/6in (14.1mm) for a width of 36in, and the allowable warpage limit is 1in (25.4mm) for 48in (1200mm).
Third, warping types Corrugated board warping types can be cited as follows:
(1) Longitudinal warpage (2) Lateral warpage Tensile warpage such as warping of warp in the longitudinal and transverse directions. Lateral warping is divided into upward warping and downward S warping.
Fourth, the main cause of warping The cause of warping is very complex, summed up is due to the fact that noodle paper (ie, corrugated paper, paper and paper) in the production due to a variety of reasons caused by their expansion and contraction differences.
The cause of warping is:
1 The nature and type of paper;
2 Moisture, heat, and tension The nature and type of paper.
1, the nature and type of paper:
In terms of the nature of the paper, the paper absorbs water and swells, drying shrinks. The wet paper has the property of absorbing large water. The size of the change in size is more than twice as large in the horizontal direction than in the vertical direction.
The type of paper, such as the degree of stretching of kraft paper and tea board paper, varies depending on the composition of the fibers and the manufacturing method. The same kind of paper may be of different grades, and warpage tends to occur when the two grades of corrugated paperboards with great differences are registered in the A-level and the C-level.
2, moisture, heat, tension in the corrugated board processing process, single-sided corrugating machine and the paste machine at the glue, the glue contains a lot of water, and then heated to dry, this situation the impact of warpage Great. It also causes uneven gluing on machinery and operation, resulting in inconsistent moisture in the cardboard. Japan’s survey of 16 plants showed that the amount of single-sided corrugators is at least 2.4 g/m2, a maximum of 8.79 g/m2, and the amount of paper machine attachment is at least 2.8 g/m2. 18.6 g/m2. In addition, with respect to the horizontal attachment fluctuations of corrugated cardboard, the survey results also confirmed that the single-faced corrugating machine is 0.5-3.5 g/m2, and the paper-bonding machine is 0.5-14.7 g/m2. Explain the uneven moisture content.
With respect to the heating problem, when a double-sided machine is used, single-faced corrugations absorb moisture and heat at the single-face corrugating machine, and also absorb water from the glue on the paste-gluer machine. Therefore, the single-faced corrugated cardboard tends to be horizontally stretched. On the other hand, paperboards that are in direct contact with the flatbed dryer on a double sided machine tend to shrink when dried.
In the process of production of corrugated cardboard, the tension of the paper from the paper-feeding frame to the double-machine is inconsistent. This inconsistency contributes to the inconsistency of lateral shrinkage of the paperboard.
Fifth, the main causes of various warpage and countermeasures 1, upward warpage, downward warpage As mentioned earlier, single-sided corrugated cardboard in a single-faced corrugating machine and paste and paste at the office, horizontal elongation, and Noodle paper (face paper) is in an over-dried state due to direct contact with the preheater and the double-sided plate dryer, and is fed into the corrugated cardboard after entering the cooling section of the double-sided machine. The corrugated cardboard is exposed to the air. In order to achieve moisture balance, moisture is released from the side of the single-faced corrugated sheet with a large moisture content, and at the same time shrinkage occurs; while the dried noodle sheet absorbs moisture and elongates, a warp phenomenon occurs. If the above situation is reversed (actually, the bonding speed is too high as compared with the drying capability of the flat-plate dryer), the warping occurs. (Zheng Zhengpei, Carton Machinery Branch of Shanghai Electric Group Printing & Packaging Co., Ltd.)
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