Corrugated cardboard box anti-pressure resistance formula application case analysis

Corrugated cartons have a history of more than 100 years since the beginning of development. With the continuous improvement of the overall industry of corrugated cartons in machinery and production processes, they have changed from the original hand-workshop-style production to today's multi-machine-linked production. Greatly increased production capacity while reducing production costs. Due to the advantages of the corrugated box itself, it is increasingly favored by packaging users. In the packaging industry, corrugated boxes have always had a tendency to replace wooden boxes. However, corrugated boxes themselves have some drawbacks, so they have not fully achieved this effect. For example, the water resistance and moisture resistance of cartons, breakage resistance, puncture strength, and compressive strength are all lower than those of wooden boxes, and compressive strength is often an important physical indicator for cartons for various cartons. In today's increasingly fierce market economy, how to maintain or reduce the cost of raw materials while ensuring the compressive strength of the carton has always been a difficult and important point in the management process of each carton manufacturing enterprise.

In fact, the compressive strength of corrugated boxes is a more complicated issue because the baseboard and corrugated base papers that make up the corrugated board are anisotropic, non-uniform, and the fibrous material is also viscoelastic in the making of boxes. During the board process, the base paper is subjected to different temperatures, adhesives, and external forces. Many changes have taken place in itself, so the change between the base paper and the corrugated board and the physical properties of the corrugated box is irrelevant, and how Calculating the physical properties of paperboard and cartons from the physical properties of the base paper has been a subject of discussion in the carton research and manufacturing industry. There are many formulae for this type of calculation in foreign countries, but since they are very complicated and difficult to understand, it has been difficult to apply them to the corrugated box industry in China for a long time. Any theory must be validated several times in the production process of an enterprise in order to accurately serve the production guidance of the enterprise.

Since June 2004, the author has successively published the calculation formula of the compressive strength of corrugated boxes calculated by the author in various publications of corrugated boxes—the formula of resistance. After receiving phone calls from some carton plant technicians, he consulted with the specific use of the anti-formula formula. Situation and discuss the deviation between the calculated value and the measured value. Due to the different production processes of the carton companies, the compressive strength of the carton after production of the same raw materials is also different, and how to find the root cause of the pressure problem in the production process of the company, so that the physical index of the raw paper in the production process is the most effective conversion As for the many reasons that affect carton pressure resistance, it has been a long-term issue for production managers.
The following elaborates on some related issues. The discussion in this article only represents the author's personal point of view.

Test, record and analysis of compressive strength of a corrugated carton

The compressive strength of a corrugated carton is the maximum load and the amount of deformation that occurs when the pressure tester uniformly applies dynamic pressure to the housing.

The entire process of compressive testing is divided into four phases (Illustration 1)

A is a preloading stage to ensure that the carton is in contact with the press platen;

B is the stage where the transverse pressure line is pressed down. At this time, the deformation amount changes greatly when the load increases slightly;

C is the side of the carton pressure stage, when the load increases rapidly, the increase in the amount of deformation is slow;

D is the crush point of the carton when the carton is completely destroyed.

The intrinsic quality of the carton is different. The change in each test phase is also different. In the entire pressure-bearing process of the carton, the four corners are mainly subjected to force, which accounts for about two-thirds of the total force, so we should Minimize the damage to the corrugations around the four corners of the carton. We can establish the relationship curve between the pressure load and deformation, and then judge the compressive strength of the carton. The deformation is extremely important.

Compressive logging: General compression tester can only record and print the final value of the compression test, that is, the final deformation and final force value of the compression test. We need to analyze the intrinsic quality of the corrugated box from the deformation and force values ​​of the compression test. It is necessary to record the changes in the amount of deformation and force throughout the process. The internal quality of the carton is different. During the compression test, The curve of the formation of force value and deformation amount is also different.

(to be continued)