Analysis of Influencing Factors of Corrugated Board Quality--Board Flatness

Some of the problems encountered in the production of corrugated board are related to the flatness of the board, the bonding of the board, the thickness of the board, the dimensional accuracy of the board, the regularity of the stacking, and the defects of the board.

Flatness of cardboard

In the production of corrugated board, sometimes some paperboards will have the problem of unevenness in the running direction of the production line. This defect is called "end-to-end" warping. This happens rarely, and it can usually be done on the double-sided machine. Adjust the tension of the cardboard to correct it. However, it is more common that the board is uneven in the direction perpendicular to the running direction of the production line. When the board is post-processed, it causes many problems such as "warping."

The moisture content of the paper roll is one of the important factors that cause warpage. Therefore, it is necessary to know the moisture content of each paper roll in order to pre-arrange corrective measures before producing the corrugated paper board. Each roll may have a different moisture content. Wet stripes are formed during the papermaking process. The corrugated paperboard production line is not equipped to balance the water content in the width direction of the paper. If the paper width (inches) is multiplied by the difference (%) in water content. If the value is greater than 40, the wet stripe will affect the flatness of the paperboard.

In addition, any abnormal operation in the operation of the corrugated board production line will cause warpage. The board produced from the corrugated board production line will take at least 8 hours to stabilize the moisture content. It should be noted that the surface and inner paper do not necessarily have the same water content, and the change in water content also depends on the amount of paper in the surface and the paper. The best surface and the paper have the same basis weight.

1. The importance of leveling

When the board is sold directly as a finished product, warpage is often considered by the user to be a quality problem and becomes a source of wringing. Further, the flatness of the corrugated board has a great influence on the subsequent processing operations.
In the automatic stacker, the cardboard must be flat and settled before it can be conveniently transported by the roller conveyor. The stability of the stack is very important for the transfer from the terminal of the corrugated cardboard production line to the warehouse, and then transferred from the warehouse to the post-processing equipment.

The automatic feeder of the post-processing equipment cannot accept over warped cardboard. Warped cardboard can cause jams and machine shutdowns, greatly reducing production efficiency. At the same time, if the post-processing equipment is unable to deliver the paperboard consistently, it will result in inaccurate printing counts and die cutting operations.

Cardboard warpage can also lead to sticky and sticky boxes. In addition, cardboard warpage can reduce the compressive strength of the carton because the wall deflection causes the carton to collapse.

2. Warpage measurement

In order to make various adjustments in the corrugated board production line to smooth the warpage and also to control the quality of the board inside and outside the factory, the degree of warpage needs to be measured.

(1) The degree of warpage is measured by the bending value f (in mm) of the cardboard. To measure the degree of warpage, there is no unifying method. According to C, D, the bending value f and the distance L between the two ends of the cardboard can be determined by the following method: that is, using a pen tip to trace the warping curve of a cardboard.

The warping factor (WF) can be calculated using the following formula:

14650 ·f
WF = -2-----
L

L is the width (in mm). If the warp factor (WF) of the board is not more than 0.25, the board is considered to be flat. The allowable warping factor can also be determined using Table 1.

(2) Measure the degree of warpage by warping the radius of the cardboard in the garden

Cardboard warpage (below):

T = 1/R

Among them, R is the radius of the circle. According to this method, the board warp degree can be measured very quickly with a very simple instrument.

3. Warping correction

To correct normal warpage, the moisture content of the paper should be reduced, and the moisture content of the paper should be increased. If the warp is corrected, the operation is reversed.

(1) Reducing the number of cardboard boards on the bridge so that the speed of single-sided machines and double-sided machines
(2) Set the sprinkler volume of single-faced corrugated paper to a minimum or total stop. If this device is present, place it on the preheater.
(3) Increase the winding angle of corrugated paper on the single-sided machine preheater.
(4) Increase the winding angle of single-faced corrugated paper on the double-sided machine preheater.
(5) Reduce or limit the wrapping angle of the tissue on the preheater.
(6) Decrease corrugating medium preparation if it does not affect the formation of corrugation
(Preparatory) jet effect.
(7) If the adhesive is not affected, reduce the adhesive supply to the single-sided machine.
(8) If a belt sprayer is installed on the corrugated board production line, stop spraying.
(9) If the paper is very wet, the speed of the corrugated cardboard production line can be reduced.
(10) Reduce the pressure on the upper belt to reduce the heat transfer on the double-sided machine.
(11) Heating of single-sided corrugated cardboard using two preheaters of a double-sided machine
(Double winding).
(1 2) Facing the corrugated groove of the paper and the surface of the preheater tube of the single-sided machine.

Reverse warping is corrected as above, but reversed. In addition, considering the economic factors, warping is not corrected by adding more binders to further humidification.

(to be continued)