The flatness of corrugated board paper is one of the important indicators in carton production technology, and it is directly related to the quality of product printing, die cutting or slotting. The flatness of corrugated paper is poor, which will produce various arch shapes of corrugated paper, and it is easy to jam during mechanized adsorption printing and cause the paperboard to be scrapped and forced to stop for cleaning; two-color printing or multi-color printing is prone to uneven ink and color registration. There are gaps in the overlapped edge of the color, etc.; the size of the slot on the printing machine is shifted, the upper and lower flaps of the carton overlap or do not fit; the die-cutting feed will also cause jams and size shifts, which may cause the positive cardboard to be defective, or The equipment was damaged and was forced to shut down for cleaning. In short, poor cardboard flatness will cause inconvenience in feeding and increase the number of waste products in the production process.
The appearance and shape of corrugated cardboard with poor flatness
The appearance and shape of corrugated cardboard with poor flatness can be roughly divided into three types: horizontal arch, longitudinal arch and arbitrary arch.
Lateral arch refers to the arch along the corrugated direction. Longitudinal arches refer to the arches produced by the cardboard along the speed of the production line. Arbitrary arch refers to an arch that undulates in any direction. The arched surface of the facial paper is called positive arch, the arched surface of the inner paper is called negative arch, and the undulating surface of the inner paper is called positive and negative arch.
The main reason that affects the flatness of cardboard
1. Different types and grades of lining paper. There are imported, domestic kraft paper, imitation kraft paper, corrugated paper, teaboard paper, high-strength corrugated paper, etc., and are divided into A, B, C, D, E, and grades. According to the poor quality of the paper, the surface paper is generally better than the inner paper.
2. The main technical parameters of lining paper are different. From the carton performance requirements or from the user’s consideration of reducing costs, the surface and the paper of the carton are required to be different, usually:
(1) The basis weight of the noodles and lining paper is different. There are some paper with a larger basis weight than the inner paper, and some with a smaller weight.
(2) The moisture content of the paper in the tissue is different. Due to the different environmental humidity of the supplier, transportation inventory, etc., some paper has a higher moisture content than a inner paper, and some have a lower moisture content.
(3) The basis weight and moisture content of the dough and paper are different. One is that the basis weight of the tissue paper is greater than that of the lining paper, and the moisture content is greater than or less than that of the lining paper. The second is that the basis weight of the top paper is smaller than that of the lining paper, and the moisture content is greater than or less than that of the lining paper.
3. The moisture content of the same batch of paper is different. The moisture content of one part of the paper is higher than that of the other part of the paper or the other part of the roll paper, the moisture content between the outer edge side and the inner core side is different.
4. The length of the (wrap angle) heating surface of the paper heat exchanger is improperly selected and adjusted or the length of the (wrap angle) heating surface cannot be adjusted arbitrarily. The former is due to improper operation, and the latter is due to equipment limitations, which affects the effect of preheating and drying.
5. The steam spray device cannot be used correctly or there is no spray device on the equipment, so the humidity of the paper cannot be increased arbitrarily.
6. After the paper is preheated, the time for dissipating moisture is insufficient, or the environmental humidity is high, the ventilation is poor, and the production line speed is improper.
7. Improper and uneven glue application of single-sided corrugating machine and gluing machine leads to uneven shrinkage of imported cardboard.
8. Insufficient steam pressure, instability, damage to accessories such as traps, or failure to drain the water in the pipeline causes the preheater to fail to work normally and stably.