Method for improving the flatness of corrugated cardboard

Corrugated board flatness is one of the important indicators in carton production technology, which is directly related to the quality of product printing, die cutting or slotting and corner cutting. The flatness of corrugated cardboard is poor, which will produce various arch shapes of corrugated cardboard. It is easy to get stuck when mechanized adsorption printing and cause the cardboard to be scrapped and forced to be shut down for cleaning; in two-color printing or multi-color printing, it is easy to produce uneven ink and color registration. There are gaps in the standard and color overlays; the slot size displacement on the printing machine, the carton lids on the top and bottom of the carton overlap or not fit; die cutting and feeding will also cause jams and size displacement and other disadvantages, which may lead to secondary waste of positive cardboard, or The equipment was damaged and forced to shut down to clean up. In short, the poor flatness of the cardboard will make the feeding inconvenient and cause the increase of secondary waste products in the production process.

In order to improve the flatness of the corrugated physical class, ensure the product quality qualification rate and normal production efficiency, we have continuously tested and analyzed in the carton production practice and found out some improvement methods. It is briefly summarized below for reference only.

The appearance of corrugated cardboard with poor flatness

The appearance shape of corrugated cardboard with poor flatness can be roughly divided into three types: horizontal arch, longitudinal arch and arbitrary arch.

Horizontal arch refers to the arch produced along the corrugated direction. Longitudinal arch refers to the arch 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 paper is called a positive arch, the arched surface of the paper is called a negative arch, and the surface of the paper is uneven and called a positive and negative arch.

Main reasons affecting the flatness of cardboard

1. Different types and grades of face paper. There are imported, domestic kraft paper, imitation kraft paper, corrugated paper, tea board paper, high-strength corrugated paper, etc., and are divided into A, B, C, D, E, grade. According to the poor quality of paper, general facial paper is better than inner paper.

2. The main technical parameters of the face paper are different. From the carton performance requirements or the user's cost reduction considerations, the paper on the side of the carton is required to be different, usually:

(1) The amount of paper on the face is different. Some tissues have a larger basis weight than the inner ones, and some have smaller ones.

(2) The moisture content of paper in tissue is different. Due to the different environmental humidity of the supplier, transportation inventory, etc., the moisture content of the facial paper is larger than that of the internal paper, and there are also small ones.

(3) The paper weight and moisture content of the surface paper are different. One is that the amount of facial paper is larger than that of paper, and the moisture content is larger than that of paper or smaller than that of paper. The second is that the amount of facial paper is less than that of paper, and the moisture content is greater than or less than paper.

3. The moisture content of the same batch of paper is different. A part of the paper has a moisture content greater than that of another part of the paper or tube paper, and the moisture content of the outer edge side and the inner core side is different between the two ends.

4. The length of the heated surface (wrap angle) of the paper passing through the heater is improperly selected and adjusted or the length of the heated surface (wrap angle) cannot be adjusted arbitrarily. The former due to improper operation, the latter due to equipment limitations, affect the preheating drying effect.

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 to distribute moisture is insufficient or the ambient humidity is large, the ventilation is poor, and the production line speed is inappropriate.

7. The single-sided corrugated machine and glue coating machine have inappropriate and uneven gluing amount, and the imported cardboard shrinks unevenly.

8. Insufficient steam pressure, instability, damage to traps and other accessories, or water in the pipeline is not drained, resulting in the preheater not working properly.

Related factors, parameter testing and qualitative analysis

Aiming at the problem of how to improve the flatness of paperboard, we have tested and briefly qualitatively analyzed the relevant factors and parameters of the physical properties and process equipment of several commonly used papers.

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