Improve corrugated box compressive strength

With the rapid development of China's market-oriented economy, the demand for foreign trade exports is increasing day by day, and the export of goods has become more frequent. In order to achieve the purpose of protecting the goods, the customer's requirements for the carton as the outer packaging of the goods are also increasing. Then, how to improve the compressive strength of corrugated boxes has become an important issue before us.

We know that the compressive strength of corrugated boxes is determined by the following two aspects:

1. Basic factors: It is the main factor that determines the compressive strength of corrugated boxes. It is an unavoidable factor. Including: the strength of the base paper, the corrugated type of corrugated board, the type of corrugated board, the moisture content, and other influences of the external environment in circulation.

2. Variable factors: Factors that can be avoided during the design or manufacture of corrugated boxes, including: box size ratio, printing area and printing design, opening area and location of openings, and carton manufacturing technology issues. Boxing machine defects, quality management issues.

Then, when we calculate the compressive strength according to the customer's requirements, and through the calculation of some empirical formulas, the paperboard is equipped with the appropriate paper (that is, the basic factor that determines the compressive strength of the carton). How can we maximize the physical properties of the base paper in the carton production process? This is the topic we are talking about today.

We already know that the factors that affect the compressive strength of carton, in addition to the basic factors such as the strength of the base paper and the shape of the crucible, are also influenced by variable factors such as the box size ratio, printing area, and design and manufacturing techniques. Then, adjusting and improving the variable factors that affect the compressive strength of cartons has also become a means to improve the compressive strength of corrugated cartons. Completing a good quality carton is actually a process of teamwork.

During the entire process from the design to the production of the carton, all departments should pay attention to the influencing factors of their work on the compressive strength of the carton, avoid or reduce the influence of these factors in their respective working processes, and make the physical properties of the raw materials into the carton physics. The conversion of the properties is optimized to produce a corrugated box with excellent compressive strength. First of all, starting from the quality control of the raw paper used as raw materials for cartons, the quality inspection department should do a good job in the inspection of incoming raw materials to ensure that the incoming raw materials meet the required physical indicators, and record the various indicators for future inspection. When the customer has a compressive requirement for the carton, the business department or technical department must use this as a basis to calculate the used paper and ensure that the used raw materials have a reasonable mix. Because the operating level and equipment status of each company are different, the theoretical compressive strength calculated based on the compressive experience formula of the business is usually higher than 10% of the customer's required compressive strength, and the produced cartons can meet the customer's requirements. Claim. Some manufacturers will be even higher. This data can be obtained through the accumulation of data.

Secondly, during the design stage of the carton, the business and design department must fully consider the structural factors that affect the compressive strength of the carton: mainly including the perimeter of the box, the aspect ratio of the box, the aspect ratio of the box, and the printing of the box surface. The area and location of the opening in the tank wall. The average customer will specify the size of the carton, and some customers will require the carton manufacturer to design. When the customer's product is bulk cargo, the business must fully consider the length of the carton and the aspect ratio. The perimeter is kept constant, and the higher the aspect ratio, the higher the compression resistance of the 1.4 carton. If only the pressure resistance of the corrugated box is taken into account, the ideal ratio is 1.2 to 1.4. Of course, in the actual design process, factors such as placing in the container transport process must also be considered. In addition, the design department should also consider the position and shape of the printing layout and die-cut holes when carrying out the carton design. Since the pressure of the corrugated cardboard is mainly determined by the shape and structure of the corrugated medium, the corrugated shape of the cardboard should be avoided as much as possible during the design process. Such as excessive printing area, full-page printing, horizontal strip printing, multiple overprint, etc. will seriously damage the shape of the corrugated medium, thereby reducing the compressive strength of corrugated boxes. After printing on corrugated boxes, the compressive strength will be lost by about 5%, and some will reach 45%. In general, some interior goods may require handling or ventilation, and often require die-cutting on the side walls, ventilation holes, and the like. However, regardless of the kind of hole to be played, the following principle must be followed: that is, the number of damaged corrugated sheets should be as small as possible, and the opening position should be as far away as possible from the corner of the corrugated box. For example, when the carton size is 405×270×270mm, when the Φ30mm round hole and the Φ15mm×75mm long hole are punched at the same position on this carton, the carton compression resistance is 89% and 92.2% of the unpunched carton, respectively. Although the area of ​​the long hole of Φ15mm×75mm is larger than that of the hole of φ30mm, since the number of corrugated plates that are destroyed is small, the impact on the compressive strength of the carton is also small. In addition, the different arrangement of the vent holes has different effects on the compressive strength of the carton. The following figure shows the order of compressive strength for different arrangements of Φ20 mm round holes and 65 mm×10 mm long holes. Therefore, in the design stage, the impact of various factors on the compressive strength of the carton must be fully considered, and a scheme with a small impact on the compressive strength should be adopted as much as possible.

Thirdly, monitoring points are set in the process that has a great impact on the carton pressure resistance in the production process, so that the variable factors of the carton manufacturing process can be effectively monitored, and problems can be discovered as soon as possible to minimize the loss. In general, the factors that affect the carton pressure resistance in the cardboard production process are: the degree of wear of the corrugating roller; the temperature of the corrugating roller and the preheating cylinder; the amount of glue applied is too large; the gap between the double-sided machine and the riding roller; the paper tension and moisture in the surface. Inconsistent cardboard warpage; width and depth of transverse pressure lines in corrugating machine. In order to effectively control the influence of the above factors, the quality inspection department must detect and record the following items when producing cartons with pressure resistance requirements: a. Board thickness; b. Adhesive strength of the board; c. Moisture of the board; d. Line width. When the problem occurs, by comparing the records recorded each time the same or similar carton is produced, the problem is found by searching for the cause and correcting the error to prevent the recurrence of the problem. In addition to the above items, the technical department should regularly check the shrinkage rate of each corrugating roller to analyze the wear of the corrugating roller, and periodically maintain or replace the corrugating roller to prevent the corrugating from forming due to wear of the corrugating roller. . In the process of carton rear section, the factors influencing the carton pressure resistance are: the gap of the paper feed roller of the printing machine; the printing pressure; the excess indentation; the depth of the carton slot; the thickness of the carton corrugated caused by the die-cutting pressure and the retraction sponge. Loss; the distance from the front and the rear nail of the nail box to the pressure line. In order to effectively control the above items, the quality inspection department shall inspect and record the following items: a. The thickness of the blank part after the board printing; b. The thickness of the printing part; c. The compressive strength of the empty box before printing; d. After printing Carton compressive strength. In addition to carefully adjusting the feed roller gap and the printing pressure during the production process, the operator of the printing department must also carefully adjust the position and the clearance of the paper feed roller and the position and pressure of the paper strip; and carefully clean up the printing in daily maintenance. The ink is accumulated on the roller and the pressure roller to avoid printing pressure and excessive indentation caused by the accumulation of ink. The die-cutting process must ensure that the pressure control can be rolled through 80%, and other parts must be solved by adjusting the blade or pad. In addition, as long as the retreating sponge can be retracted, excess sponge should be removed to prevent excessive damage to the corrugation strength. The nail box should ensure that the distance between the front and rear nails from the midpoint of the transverse pressure line is controlled within the range of 13±7mm.

In addition, the storage and transportation department should minimize the number of handling during storage and transportation. Bare loading and unloading, pedaling, etc. will affect the compressive strength of the carton.

In short, through the coordination and cooperation of various departments, we must make concerted efforts to ensure that we do our job and maximize the physical properties of raw materials to the physical properties of corrugated boxes. It will no longer be difficult to produce corrugated boxes that meet our customers' requirements.

Author: ZHANG Shu right assistant manager