Cardboard Flatness Best Solution--Board Warping Detailed (4)

Synchronous speed control system is an important tool for controlling board warpage

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 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. That is to say, when the bridge is normally loaded with full stacking, the paperboard produced is a straight bridge with no load, and the warpage of the cardboard is shifted in the reverse direction: it remains unchanged under other operating conditions.

We want to make the warpage of the board offset in the opposite direction. It is a good find to use a single-sided web shower. 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 varies from 100 feet to 550 feet/minute, the change in warpage is less than 6 millimeters.

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 a main board warpage control device, the speed synchronization system has other advantages: the control of the board warpage, the input required for the synchronous engagement system, the elimination of manual control of overpass paper by the operating personnel, and the focus on other matters to prevent the bridge product When the number of paper sheets is too large, the single-sided paper sheet is warped upwards, which prevents the single-sided paper sheet that is wasted when the overbridge paper is accumulated in space to be broken.

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 accumulated paper on the bridge, the amount of adhesive used, the production speed, etc., the warpage problem of the board can be greatly improved. However, the quality of the paper is uneven, and the inconsistent moisture content is the single 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 fabrics because of their corrosion resistance.

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 backing paper at the first bonding position of the double-sided backing 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 change in the moisture content of both webs increases or decreases in the same direction, the relationship between the moisture content of the webs remains approximately the same, so the warp shape of the paperboard remains the same. When the bridge is loaded with paper, the same speed (and dryness) of the single-sided paper web and the double-sided bottom paper running at different speeds and degrees of drying are combined to form the difference in the dryness of the two paper webs. Change the relationship between their respective moisture content at the double-sided adhesive point, and thus the warpage shape of the paper guide 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 warping of flat cardboard. Therefore, as long as there is a 2% moisture content that changes the most, it will cause a large amount 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.

(to be continued)