Corrugated board production line process improvement

China's packaging industry started from the 1980s and has rapidly developed into a complete system with considerable scale. It has ranked 16th among 40 industries in the national economy. Due to the increased awareness of protecting human living environment, corrugated cartons have always been the most favored packaging material in the packaging industry. It is also a widely used container for circulation of general manufacturing materials, and its presence is almost everywhere. , but as long as you pay attention, you will find that some cardboard boxes are not damaged, are inconsistent, and even appear peeling and brittle. The reason for this is mostly caused by the coldness of people, machines, materials, methods, and rings. of.

According to incomplete statistics, the corrugated cardboard production line in China increased from 18 in 1980 to 181 in 1990, of which 113 were imported from the United States, Japan, Italy, and other countries.

From 1990 to 1999, the technology of domestic paperboard production lines gradually matured, and the trend of the country's on-line production has soared. In the past ten years, about 100 production lines have been added each year. Currently, there are as many as 1,300 cardboard production lines in China. Computer control has been extensively applied to the large-scale and high-speed development. However, up to now, the dryer heating plate of the paper and board production line still cannot adapt to the changes in various grades, weights, and speeds of the paperboard. Therefore, the economic benefits of the equipment still have potential to be tapped. Here only some suggestions for rationalizing the deficiencies of the dryer process.

1. Domestically produced corrugated board production line The conventional double-sided machine drying section heating and pressurizing mechanism consists of a fixed heating plate and a gravity roller pressure device. The heat transfer is a fixed value when the two devices are running at different speeds. During the process of producing the paperboard, the heat quantity of the heat plate is adjusted according to the paper grade, basis weight, and thickness, so as to meet the heat supply requirements of different paperboards. . However, in the production process, especially in the production of low-grade corrugated paperboard, due to the lack of paperboard tension, the original joints, notches and breakages often cause the paperboard production line operating speed to change (without full-automatic paper receiving device). Any significant speed change will break the balance of heat transfer, while the conventional double-sided dryer hot plate is fixed and cannot be adjusted. At this time, the paperboard's “ten time” is in a heated and pressurized state. Excessive heat causes the paperboard to be overheated, resulting in excessive lateral shrinkage of the corrugated paperboard (warpage), a brittle and squib-like shape, and even rupture at the pressure line, etc. Ultimately, the resulting corrugated board has reduced compression strength, inaccurate print overprinting, and damaged cartons.

Figure 1 Hydraulic Lifting Schematic

Second, according to the heat transfer balance, the supply of corrugated board heat in the hot plate must adapt to the corrugated board production line operating speed. The type of base paper, which is the key to making uniform texture, not bending, and not crunchy cardboard. The heating plate of the double-sided machine, which is often present on the corrugated board production line, can be designed as a hydraulic heating system with variable heat. Because it is impossible to change the temperature of the hot plate in actual production, only by adjusting the inclination of the hot plate, the hot plate forms a wedge with a corrugated paperboard, and a certain gap is created to allow part of the heat to escape from the gap. Reducing the heat supplied by the hot plate to the corrugated board to achieve the purpose of heat transfer balance, ensuring that the corrugated board can effectively adjust the supply of heat according to different corrugated board drying requirements when passing through the double-sided dryer, and ensure various technical specifications of the corrugated board. Hydraulic lift working principle shown in Figure 1.



Fig. 2 Schematic diagram of interlayer heating plate drying method

three. The existing corrugated board production line of fixed hot plate device can not be transformed into a variable heat heating system (if change, unless spending a lot of money to transform it), an air injection system can be designed, that is, the heat drying method . It is designed to install a narrow nozzle in the gap between the hot plate, with a set of air-conditioning valve, according to the size of the cardboard speed and adjust the valve opening and closing angle to control the amount of air injected into the nozzle, The air forms a thin air layer between the hot plate and the corrugated cardboard to reduce the heat transfer of the hot plate to the corrugated board. The principle is that when the running speed of the corrugated board production line is reduced, the regulating valve is opened so that the hot fired board and the cardboard are The air diffuses to form a flake of air-like strands that just hold the corrugated board and canvas belt from the hot plate, thereby reducing the heat transfer to the board from excessive heat (see Figure 2).

(Author: Guiyang Huangguoshu Paper Co., Ltd.)