Improved flatness in corrugated board production practice (1)

The flatness of corrugated board is one of the important indicators in the carton production technology. It is directly related to the quality of product printing, die cutting or notching. The poor smoothness of corrugated paperboard will result in the multi-arched shape of corrugated paperboard, and it will be easily jammed due to mechanized adsorptive printing and cause the paperboard to be scrapped and be forced to shut down and clean up. Ink printing is not uniform and color registration is not allowed in double-color printing or multi-color printing. There are voids on the edges of the color stack; slots are displaced on the slotting machine, and the carton overlaps or does not overlap the flaps; die-cutting feeds can also cause problems such as jams and dimensional displacements, which can lead to scrapping of the positive paperboard or damage to the equipment. And forced to shut down finishing. In short, the poor flatness of the paperboard will cause inconvenience in feeding and increase the number of secondary waste products in the cattle production process.

For the factory to improve the flatness of corrugated board, to ensure product quality pass rate and normal production efficiency, we constantly test and analyze in the carton production practice, and explore some improvement methods. It is summarized as follows.

Corrugated paper sheet poor appearance appearance shape

Corrugated cardboard poor appearance of the shape of the general can be divided into three types: horizontal arch, longitudinal arch and arbitrary arch.

Lateral arching refers to the arching that occurs along the corrugated direction. Longitudinal arching refers to the arched shape of the board along the line speed of the production line. Arbitrary arches mean undulating arches in any direction. The surface of the dough paper is arched in the form of a positive arch, the arched surface of the paper is called a negative arch, and the surface of the paper and the surface of the paper are undulated and called positive and negative arches.

The main reasons affecting the flatness of the board

1. Face paper types and grades are different. There are imported, domestic kraft paper, imitation kraft paper, corrugated paper, tea board paper, high-strength corrugated paper, etc., and points A, B, C, D, E, grade. According to the paper quality material, the general paper is better than the paper.

2. The main technical parameters of the paper are different. Considering the performance requirements of the carton or the user to reduce the cost, the paper inside the carton is required to be different, usually:

(1) The amount of paper in the dough is different. There is a large amount of face paper than the paper, and there are also small ones.

(2) The moisture content of the paper in the facial tissue is different. Due to the different environmental humidity of suppliers, transportation stocks, etc., there is a large amount of moisture in the facial tissue than in the paper, and there are also small ones.

(3) The amount of paper and moisture content in the surface are all different. One is that the dough paper is greater than the paper, and the moisture content is greater than the paper or less than the paper. The second is that the surface paper is less than the paper, the moisture content is greater than the paper or less than the paper.

3. The moisture content of the same batch of paper is different. Part of the paper moisture content is greater than the other part of the paper or paper between the ends of the outer edge and inside; the core side of the water content is different.

4, paper through the preheater (wrap angle) heating surface length is not properly selected and adjusted (or wrap angle) heated and the length can not be arbitrary, affecting the preheating drying effect.

5. The steam spray device cannot be used correctly or there is no spray device on the device, so the humidity of the paper cannot be arbitrarily increased.

6. After the paper is preheated, the water is not distributed in sufficient time or the environment is humid, ventilation is poor, and the production line speed is not proper.

7. Single-sided corrugating machines, glue dispensers have improper sizing, uneven feeding, and uneven cardboard shrinkage.

8. Inadequate steam pressure, instability, damage to steam traps, etc., or net draining of the water in the pipeline may prevent the preheater from operating normally.

Related factors, parametric testing and qualitative analysis

For the problem of how to improve the flatness of the paperboard, we tested and briefly analyzed the physical properties, process equipment, and other related factors and parameters of commonly used papers.

(1) The quantitative increase of the same type of paper, the shrinkage rate is slightly reduced. The relationship among the imported kraft paper, domestic beef (imitation) leather paper, tea board paper, high-strength corrugated paper, the quantitative, moisture content, shrinkage ratio.

(2) The steam pressure supplied by the corrugated board production line is directly proportional to the surface temperature of the preheater. The higher the air pressure, the higher the surface temperature of the preheater.

(3) Paper with high basis weight and high moisture content is preheated and dried slowly, but vice versa. Papers with different basis weight and moisture content are preheated and dried on a preheater with air pressure of 1.0Mpa/cm2 (172°C).

(4) The greater the length of the heating surface (wrapping angle) when the paper is dried on the preheater, the lower the water content. The relationship between the length of the heating surface and the moisture content after baking was determined at a preheater temperature of 172°C and a line speed of 0.83 m/s for papers of different basis weights with a moisture content of 10%.

(5) After the single-faced corrugated paper is warmed up, natural moisture is emitted slowly, and the fan ventilation releases moisture quickly. The water content after preheating of 220g/m2 and 150g/m2 single-faced corrugated paper after 172g/m2 preheating was 13%, and the natural distribution of moisture in the greenhouse at 20°C and humidity 65% ​​was compared with that of fan ventilation.

(to be continued)