# Calculation of compressive strength of corrugated boxes

The corrugated box is made up of corrugated base paper of various layers. The compression formula of corrugated box is based on the physical properties of the cardboard base paper. The compressive strength of the corrugated box is calculated. We can select a certain corrugated board base paper according to the compressive strength requirement of the corrugated box. . Only by clearly understanding the various properties of the base paper, in the next step, according to the needs of production, various types and various specifications of paper can be combined and configured to produce products that meet the needs of users.

In fact, the compressive strength of corrugated boxes is a more complicated problem, because the box base paper and corrugated base paper constituting the corrugated board are anisotropic, uneven, and the fiber material also has viscoelastic properties. During the process of the board, the base paper is subjected to different temperatures, adhesives and external forces, and many changes have taken place. Therefore, the change from the base paper to the corrugated board and the physical properties of the corrugated box is not oriented, and how Raw paper physical properties Calculating the physical properties of cardboard and cartons has been the subject of discussion in the carton research and manufacturing industry. In order to better produce all kinds of carton products, it is necessary to understand some of the knowledge of raw paper paper performance testing.

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Compressive strength calculation

There are many calculation formulas for the existing compressive strength, but most of them are used abroad, which are difficult to understand and memorize, and it is difficult to master the existing corrugated box designers in China. Among the enterprises, the difficulty of pressure-resistant design often makes the price design and the carton compressive strength design separate, which is easy to cause waste of raw materials or quality problems of insufficient pressure resistance. In the connection between design and production, the anti-clause formula avoids the blindness in the design and increases the predictability of the compressive strength of the carton at the beginning of production.

The corrugated box is made up of corrugated base paper of various layers. The anti-correlation formula calculates the compressive strength of the carton according to the physical properties of the cardboard base paper to see if it can meet the requirements. It can also choose a certain amount according to the compressive strength requirements of the corrugated box. Corrugated cardboard base paper.

P=PxÂ·K

Pâ€” the empty box compressive strength of the corrugated box ( in N),

Pxâ€” the transverse integrated compressive strength ( in N/cm) of corrugated board base paper.

Among them, the calculation formula of the comprehensive ring compressive strength of the three-layer corrugated cardboard base paper is:

Px=(R1+R2+RmC) / 15.2

The formula for calculating the comprehensive ring pressure of five-layer corrugated cardboard base paper is:

Px=(R1+R2+R3+Rm 1C 1+Rm 2C 2) / 15.2

Rn--- Testing force value of transverse ring compressive strength of facial tissue (N/ 0.152m )

Rmn--- Testing force value of transverse ring pressure of crepe paper (N/ 0.152m )

C--- corrugated shrinkage ratio, that is, the ratio of the length of corrugated core paper to facial tissue. (CA=1.532, CC=1.477, CB=1.361)

Kâ€” The effective value of the integrated ring pressure in the compressive strength of the empty box of the carton, the calculation formula is:

K three A=30.3+0.275Z-0.0005Z2

K three C = 27.9 + 0.265Z-0.0005Z2

K three B = 24.6 + 0.235Z-0.0005Z2

K five AA=41.7+0.355Z-0.0005Z2

K five BB = 33.2+0.305Z-0.0005Z2

K five CC=38.1+0.345Z-0.0005Z2

K five AB=38.2+0.335Z-0.0005Z2

K five AC=40.2+0.355Z-0.0005Z2

K five BC=35.7+0.325Z-0.0005Z2

Three A--- three-layer A- box , the range of three-layer box circumference: 70 -200cm

Five AC--- five-layer AC box, the range of five-layer box circumference: 70 -300cm

Each company only involves some types of defects in the production process, so it is only necessary to select the corresponding resistance formula according to the type of use of the enterprise. According to the ring pressure value of the æ¥ž type and the base paper, the integrated ring pressure is calculated, and then the circumference of the carton is brought into the calculation formula of the K value corresponding to the æ¥ž type, and the product of the integrated ring pressure and the K value is the compressive strength of the carton. We can also select the appropriate cardboard base paper according to the compressive strength and circumference of the predetermined carton, and also use the calculated compressive strength to guide the operation of each production process.

In most of the calculation formulas of compression resistance, most of them use the ring pressure of the base paper for calculation. In fact, the pressure resistance of the carton is not only the ring pressure strength of the base paper, but also the factors affecting the compressive strength of the corrugated box. For paper, it should include the paper's ring strength, tensile strength, tightness, and paper's water resistance and water absorption.

The long net paper machine and the round net paper machine have different fiber arrangement. The paper produced by the rotary paper machine is arranged in order according to the mechanical process. The pulp is not easy to hang, and the paper looks like cotton wool through the strong light. The texture is uneven, and the light transmission phenomenon is easy to occur; while the long net paper machine is just the opposite, the arrangement of the fibers is complicated, tends to be disordered, the pulp is evenly distributed, the paper looks uniform through the strong light, and there is no obvious light transmission phenomenon. Due to the different fiber arrangement, the physical indexes of the long net base paper and the round net paper are affected.

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Base paper test

For the ring pressure test, the ring pressure test of the corrugated base paper is divided into the longitudinal ring pressure strength and the lateral ring pressure strength. It is necessary to pay attention to the ring pressure test sampling test. The longitudinal ring pressure strength sampling needs to be consistent with the paper web width direction. The lateral ring pressure strength needs to be consistent with the length of the web. During the test, we will find that although the arrangement of the fibers of the long wire machine tends to be disordered, the transverse ring pressure will always be stronger than the longitudinal ring pressure. The strength is low, and as the 0201 corrugated box, the lateral ring pressure strength is consistent with the direction of the corrugated force, that is, the horizontal ring of the corrugated base paper when the paper grade is judged or the compression resistance is calculated. The compressive strength is the effective strength of the test. The long-end paper machine increases the amount of fiber tolerated during the transverse ring pressure test while performing the disordered arrangement of the fibers, thereby enhancing the transverse ring-shaped compressive strength of the corrugated base paper, and at the same time enhancing the interfiber between the fibers due to the disordered arrangement of the fibers. The firmness, in turn, ensures the stability of the corrugated box's compressive strength, so that the drop in the resistance value between the individual cartons is reduced.

Regarding the value of the ring pressure in the compression formula, we should follow the test results of the standard environment to reduce the error between the test values â€‹â€‹caused by the change of the test environment. We all know that the humidity of the air will have a certain impact on the ring pressure strength of the corrugated base paper and the pressure resistance of the carton. If the environment when testing the base paper is too dry, the force value of the ring pressure test will be higher than the actual value. If the use environment is too humid, we use this high force value for pressure-resistant design, which will inevitably lead to unsafe quality hazards; conversely, if the test environment is too humid and the use environment is too dry, the paper's ring pressure test force value It will be very low, and we use this very low force value to design the compressive strength, which will inevitably lead to waste of raw materials. When using the test values â€‹â€‹for compressive calculation, we first need to verify within our own company. Under normal circumstances, we should guarantee the safety factor of a calculated value. Generally, 1.2 is selected, that is, the calculated value is 1 , and the actual compressive pressure should be Can achieve 1.2 times the calculated value to prevent the difference between the individual carton or the change of some external environment caused by insufficient pressure.

Tensile strength, the tensile strength of corrugated base paper depends on the fiber structure of the base paper and the adhesion between the fibers. The tensile strength not only affects the tensile strength of the base paper during use, but also affects the tensile strength of the base paper. The compressive quality of the carton after molding. Under normal circumstances, if the ring pressure of the paper is good, and the crack length and tensile strength are not good, the deformation of the carton during the compression test is often large. It is shaped like an accordion. This is because the fiber's texture, structure, or the connection between the fibers is poor. When the carton is subjected to the compression test, the fiber at the edge of the crimping line is first stressed, and the loose fiber cannot be very The force transmitted by the carton is well conveyed to the whole of the carton, but the passive part is under pressure. With the partial collapse of the edge, the force part gradually moves toward the middle of the box, forming a deformation such as an accordion test. phenomenon. If the tensile strength is good, then there will be no such situation. The carton will be subjected to a lot of pressure when the deformation is small. If the code is added, the carton will collapse from the center of the box due to the overall pressure.

Paper tightness test The pressing effect of the base paper in the production process, the degree of tightness will affect the degree of tightness between the fibers and affect the ring pressure strength and tensile strength of the base paper, and zui will eventually affect the compression resistance of the carton. Strength, and due to the insufficient tightness of the paper, it also affects the moisture absorption of the carton, causing the carton to absorb excessive moisture during use or storage and reduce the compressive strength of the carton itself.

The paper determines whether the quality of the paper is determined by a single physical indicator. The physical properties of the paper should be a comprehensive indicator. In some cases, in order to prevent the carton companies from cutting corners, the carton customers have demanded too much weight on the paper, and the carton companies have to pay too much weight to meet the customer's requirements. Reduce paper grades to ensure cost. The customer's request has already rejected the low-weight and high-strength corrugated paper. In fact, considering the comprehensive performance, the low-weight and high-strength corrugated base paper is more stable than the low-grade and high-weight corrugated base paper, and Since the stability of the base paper reduces the difference between the individual physical properties of the carton, the safety of the carton is increased, and it is difficult to achieve this effect in the low-grade and high-weight paper. In the pressure-resistant design, it is difficult to accurately estimate the compression resistance due to the instability of the low-grade base paper. The physical properties of the individual after the completion of the carton are very different, and the inferior products doped in the carton are used or transported. In the process, it will become the first damage point of Zui to affect the use of the whole batch of cartons.

In the compression of the carton, the base paper plays a decisive role. We need to make a certain effort to test and judge all kinds of base papers, and properly arrange all kinds of papers to produce cartons that meet the physical performance requirements. The carton compression is a comprehensive control process. In the production, the impact on the compression resistance of the carton caused by the unreasonable process should be minimized. Losing the compressive strength of the carton is equivalent to wasting the original paper. This is a hidden waste of Zui. It is bound to create a vicious circle that will greatly increase the cost of making cartons. At the beginning of production, the performance of various base papers will be well known, and in actual production, paper can be dispensed as needed.

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