Paperboard warp issue Raiders four

3 synchronous speed control system is an important tool to control the curvature of cardboard

In the conventional production methods, most corrugated board production lines have a variety of cardboard warpages due to changes in production speed. Reducing the speed of the corrugated cardboard production line when the order was switched, or restarting after the equipment was closed, the warpage of the cardboard was particularly prominent. Therefore, continuous production of corrugated board production lines not only operates continuously, but also maintains a constant production speed so that board warpage problems tend to be minimized. To solve this problem, some suppliers of corrugated board production lines have produced synchronous speed control systems that can regulate the hot plate and preheater speed settings, which can reduce board warpage and at the same time reduce the quality problems caused by speed changes.

The tests to determine the effect of the overpass volume on the warpage of the board were carried out at various production speeds and under no-load and full-load accumulation of the bridge. Tests have shown that empty bridges are more likely to deflect the cardboard in reverse than full-loaded bridges. In other words, when the bridge is normally loaded with full stacking, the cardboard produced is flat; when the bridge is empty, the warpage of the cardboard is shifted toward the opposite direction and the other operating conditions remain unchanged.

We hope to offset the cardboard warpage in the reverse direction, using a single-sided web spray device is a good discovery. We also confirmed that previous changes in the production speed of the overpass will cause significant warping of the board; however, it is more important to find that the warpage of the board in the case of no-load on the bridge is small, a 600-mm board. When the production speed is changed in the range of 100-550 ft/min, the warpage variation is less than 6 mm.

The significance of this discovery is that it affects the speed options for automatic order switching in a continuously produced corrugated board line. Since we know that reducing the production speed will not significantly affect board warpage, we now have the option of continuous production (ie, no need to stop). That is, we only need to reduce the production speed and restore the normal speed after completing the order switch. As the main board warpage control device, the speed synchronization system has other advantages: the control of the warp of the board, the input required to provide the synchronous engagement system, the elimination of the manual operation of the operator to control the overpass paper accumulation, and the prevention of crossover accumulation. When the number is too large, the single-sided web warps upwards, which prevents the single-sided web from being wasted when crossover space is accumulated.

4 The automatic order switching system for corrugated board production lines offers several advantages.

Advantages of automatic order switching system

In high-speed operation, manual replacement of order sheets is impossible, and maintaining the chronological order of multiple devices can result in paper jams. The use of a high-speed automatic order switching system reduces clogging and compensates for potential loss of production due to reduced speed. And the automatic order switching system does not require high equipment, and the price is appropriate. During the production process, it was found that the completion of an order switch would only result in a 2 metre long web of paper waste, including those found at the splicing machine. The waste paper would be sent directly to the junk station and not to the cardboard stacking station.

The warpage shape of the board after molding is determined by the “relevant moisture content of the single-sided paper and the double-sided bottom paper at the first bonding position of the double-sided bottom paper”. For empty bridges, when the corrugated paperboard production line changes speed, the two paper webs change almost at the same time in eliminating the moisture content, both of which are less dry because the speed is lower and the speed is higher. However, since the changes in the moisture content of both webs increase or decrease in the same direction, the relationship between the moisture content of the webs remains approximately the same; therefore, the warp shape of the paperboard remains the same. When the bridge is loaded with paper, the single-sided paper web at the same speed (and dryness) is combined with the double-sided bottom paper running at different speeds (and dryness) as the speed changes, and the dryness of the two paper webs is combined. The difference changes the relationship of their respective moisture content at the double-sided glue points, resulting in a change in the warpage shape of the board. Only 1% of the moisture content will change the warpage factor of the C-type corrugated board by 3.6mm, and the warpage factor of the B-type corrugated board by 4.8mm. As long as there is a 6 mm warping factor, it is absolutely possible to cause unexpected warpage in flat paperboard, so as long as there is a 2% change in moisture content, it will cause a lot of board warpage. In order to get the best cardboard warping control, the overpass must be run without load. In normal manual operation control, overpass unloading is unrealistic because of the danger of single-sided webs coming out and jamming. The operators of single-sided machines need to pay close attention and control from time to time to prevent such situations from occurring. In addition, the overpass loading of the bridge prior to taking over the paper can prevent the loss of production during the receipt of the paper due to slower speeds of the double sided machine.

5 The location of the sprinkler system is important for controlling the warpage of corrugated cardboard

By adjusting the amount of paper coating on the preheater, the amount of paper on the overpass, the amount of adhesive used, the production speed, etc., the problem of warp in the board can be greatly improved. However, the quality of the paper is uneven, and the inconsistency in the moisture content is the most important factor in the warpage of the board.

Adding moisture to the outside of the double-sided liner at the front of the hot plate section is not a practical way to control the positive warpage of the cardboard because it will wear the tissue surface and create the underlying warpage tension and some warp-like warpage of the cardboard. Water is sprayed immediately behind the hot plate section and on the double-sided bottom paper in front of the three layers of cardboard, and the board will exhibit reverse warpage. However, the amount of warpage generated by cardboard is unpredictable. Cardboard warping is obvious when cardboard is stacked. Especially in extreme cases, careful and experienced use of this board warpage control method will successfully reduce the positive warpage of the board. Spraying water onto the face paper of a single-sided web is a very effective method to eliminate reverse warpage of the paperboard and the reversed portion of the S-shape warp. It is possible to control the warpage of the board across the width of the corrugated cardboard production line. However, water spray from a single-sided web can damage the cotton fabric conveyor belt. Adding water to the single-sided paper web between the paste-gluer and the hot plate can damage the cotton belt (rot). Adjusting the water before the single-sided web preheater will reduce this tendency. Synthetic fiber conveyor belts are more satisfactory than cotton fabric conveyor belts because of their corrosion resistance.
(to be continued)