The warping of corrugated cardboard is a very headache, which seriously affects the quality of the next printing and slitting process. Due to the warping of the cardboard, it cannot be accurately positioned when entering the printing slotting machine, resulting in inaccurate overprinting, inconsistency in the position of the slotting and cutting corners and inability to fine-tune, and sometimes creases appear on the surface of the cardboard. The reason for the warping of single-sided corrugated cardboard is very simple, that is, the moisture content of the inner and (core) corrugated base paper is inconsistent or the thickness is inconsistent. Of course, there must be a definition of "warping" to prevent cardboard from warping. The author's understanding of the meaning of "warping" is that the single-sided (see pit) cardboard is determined to be corrugated as the upper side, and the arc is bent downward (bending in the direction of the inner paper). On the contrary, it is regarded as a downward warping.
If the single-sided (see pit) cardboard is upturned, the reason is that the water content of the corrugated base paper is greater than that of the inner core paper. If it warps down, the reason is: the water content of the corrugated base paper is less than that of the inner core paper or the gram of the inner core paper is higher than that of the corrugated base paper. After determining the cause of cardboard warping, it must be solved separately according to the direction of cardboard warping. When the single-sided (see pit) cardboard of the single-sided corrugating machine is warped upward, the heat source of the corrugated paper preheating roller on the single-sided corrugating machine can be turned on, and one or two lining paper preheating roller heat sources can be turned off at the same time, and the vehicle speed shall be reduced accordingly. It is necessary to increase the heat source of the tile paper preheating roller (increase the electric heating tube, increase the air pressure, etc.) or increase the wrapping angle of the tile paper on the preheating roller. When warping, the lining paper needs to be sprayed and humidified. Make the moisture content of the inner paper and the corrugated base paper nearly the same.
When the single-sided (see pit) cardboard of the single-sided corrugating machine is tilted downward, the heat source of the corrugated paper preheating roller on the single-sided corrugating machine should be turned off, and one or two inner paper preheating roller heat sources should be turned on at the same time. speed. When there is still warpage, it is necessary to increase the heat source of the lining paper preheating roller or increase the wrapping angle on the lining paper preheating roller. The moisture content of the paper is nearly the same. S-type warpage of single-sided cardboard is generally caused by the uneven distribution of moisture in the base paper. According to the warpage, the amount of glue applied can be adjusted according to the above-mentioned causes of warpage, or the base paper with too low moisture can be sprayed and humidified locally. It is better to use a moisture tester to measure the moisture content of the inner (core) and corrugated paper respectively before starting the machine, and then control the temperature of each roller according to different moisture content. Generally speaking, when the cardboard is off the machine, keep it slightly upward (corrugated paper) warping, and adopt the forward and reverse stacking method. After about an hour, the cardboard will be completely restored to a flat state.