Calculation of compressive strength of corrugated box and test of base paper

Corrugated box is composed of corrugated base paper at all levels The compressive strength formula of corrugated box is to calculate the compressive strength of corrugated box according to the physical properties of the paper base paper We can select certain corrugated paper base paper according to the predetermined compressive strength requirements of corrugated box Only when we have a clear understanding of the various properties of the base paper, we can combine and configure various types and specifications of paper according to the needs of production in the next process to produce products that meet the needs of users
In fact, the compressive strength of corrugated box is a complex problem, because the box board base paper and corrugated base paper that make up the corrugated board are anisotropic and uneven, and the fiber material also has viscoelastic properties In the process of making the box board, the base paper is affected by different temperatures, adhesives and external forces, and has changed a lot, so from base paper to tile The change between the physical properties of the corrugated board and the corrugated box is not directional How to calculate the physical properties of the board and the box from the physical properties of the base paper has always been a topic discussed by the research and manufacturing industry of the box In order to better produce all kinds of carton products, it is necessary for us to know some knowledge of base paper performance testing There are many formulas for calculating the compressive strength, but most of them are used in foreign countries It is difficult to understand and remember them, and it is difficult for the existing corrugated box designers in China to master them But in all enterprises, because of the difficulty of compression design, the price design and the compression strength design of cartons are often separated, which is easy to cause the waste of raw materials or the quality problem of insufficient compression In the connection of design and production, the Kangshi formula avoids blindness in design and increases the predictability of compressive strength of cartons at the beginning of production Corrugated box is made up of corrugated base paper at all levels The antiskid formula is to calculate the compressive strength of the box according to the physical properties of the paperboard base paper to see whether it can meet the requirements It can also select a certain corrugated base paper according to the compressive strength requirements of the predetermined corrugated box P = PX · k p - the compressive strength of the empty box of the corrugated box (unit n), PX - the transverse comprehensive ring compressive strength of the corrugated board base paper (unit n / cm) Among them, the calculation formula of the comprehensive ring crush strength of the three-layer corrugated board base paper is: PX = (R1 + R2 + RMC) / 15.2 the calculation formula of the comprehensive ring crush strength of the five-layer corrugated board base paper is: PX = (R1 + R2 + R3 + rm1c1 + rm2c 2) / 15.2rn - the test force value of the transverse ring crush strength of the paper (n / 0.152m) Rmn - the test force value of the transverse ring crush strength of the corrugated paper (n / 0.152m) C--- Corrugated shrinkage, that is, the ratio of the length of the corrugated core paper to the face paper （CA=1.532,CC=1.477, 2 + 0.335z-0.0005z2 k v AC = 40.2 + 0.355z-0.0005z2 k v BC = 35.7 + 0.325z-0.0005z2 three a -- three-layer a-corrugated box, the value range of three-layer box perimeter: 70-200cm five AC -- five layer AC corrugated box, the value range of five layer box perimeter: 70-300cm each enterprise only involves part of the corrugated box in the production process, so it is only necessary to select the corresponding formula according to the corrugated box used by the enterprise The comprehensive ring pressure is calculated according to the ring pressure value of the corrugated type and the base paper, and then the circumference of the carton is brought into the calculation formula of K value corresponding to the corrugated type The product of the comprehensive ring pressure and K value is the compressive strength of the carton We can also choose the right base paper according to the compressive strength and perimeter of the pre-determined cartons At the same time, we can use the calculated compressive strength to guide the production process In most of the compression calculation formulas, most of them are based on the ring compression strength of the base paper In fact, the ring compression strength of the base paper is not the only one that affects the compression strength of the corrugated box There are many factors that affect the compression strength of the corrugated box, but in terms of the paper, they should include the ring pressure, tensile strength, tightness, water resistance and water absorption of the paper, etc The fiber arrangement of the long screen machine is different from that of the round screen machine The paper produced by the round screen machine is arranged in an orderly manner due to the mechanical process The paper pulp is not easy to hang evenly The paper looks like cotton floccules through the strong light The texture is not uniform and light transmission is easy to occur On the contrary, the fiber arrangement of the long screen machine is complex and tends to be disordered The hanging pulp is even and the paper is transparent Due to the different arrangement of fibers, the physical indexes of long web base paper and round web base paper are affected Base paper test Ring pressure test and corrugated base paper ring pressure test are divided into longitudinal ring pressure strength and transverse ring pressure strength During the ring pressure test sampling test, it is necessary to pay attention to that the longitudinal ring pressure strength sampling should be consistent with the paper width direction, and the transverse ring pressure strength sampling should be consistent with the paper length direction During the test, we will find that although the fiber arrangement of the long screen paper machine It tends to be disordered, and the transverse ring compression strength is always lower than the longitudinal ring compression strength As a 0201 corrugated box, the transverse ring compression strength is consistent with the direction of the corrugated force, that is to say, in the paper grade judgment or compression calculation, the transverse ring compression strength of the corrugated base paper is the effective strength of the test The long screen paper machine increases the number of fibers to bear when testing the transverse annular pressure while disorderly arranging the fibers, so as to enhance the transverse annular pressure strength of the corrugated base paper At the same time, because of the disordered arrangement of the fibers, it enhances the firmness between the fibers, thus ensuring the stability of the compressive strength of the corrugated box, so that the drop of the resistance value between the single cartons is reduced We should follow the test results of the standard environment to reduce the error between the test values 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 crush strength of the corrugated base paper and the compression strength of the cartons If the environment when we test the base paper is too dry, the force value will be higher than the actual value when we test the ring crush, and if the environment is too wet, we use this higher force value to carry out the compression design, which will inevitably cause unsafe quality hazards; otherwise If the test environment is too wet and the use environment is too dry, the force value of the paper will be very low during the ring pressure test, and we use this very low force value to design the compressive strength, which will inevitably cause waste of raw materials When using the test value for compression calculation, we first need to verify it in our own company Generally, we should ensure a safety factor of the calculated value, generally 1.2, that is, the calculated value is 1, and the actual compression should be able to reach 1.2 of the calculated value Times, to prevent individual differences between cartons or some changes in the external environment caused by insufficient compression Tensile strength, the tensile strength of corrugated base paper depends on the fiber structure of the base paper and the adhesive force between the fibers The tensile strength not only affects the tensile strength of the base paper in the use process in the machinery, but also affects the compression quality of the carton after forming In general, if the paper's ring compressive strength is very good, and the crack length and tensile strength are not good, it will often The deformation of the carton during the compression test is large, and the Zui end shape is like an accordion, because of the poor fiber texture, structure or the connection force between the fibers When the carton is under the compression test, the stress is on the fiber at the edge of the crimping line first, and this loose and weak fiber dimension can not transfer the force on the carton to the whole carton, but the passive part is bearing Pressure, with the local collapse of the edge, the stress part gradually moves towards the middle of the box, forming a deformation like an accordion test phenomenon If the tensile strength is very good, this kind of situation will not occur The carton will bear a lot of pressure when the deformation is very small If we add another code, the carton will collapse from the center of the box surface because the whole carton cannot bear the pressure Paper tightness test the squeezing effect of the base paper in the production process The compactness will affect the fastness between the fibers, and then affect the ring compression strength and tensile strength of the base paper Zui will eventually affect the compressive strength of the cartons, while due to the insufficient tightness of the paper, it will also affect the moisture absorption of the cartons, making the cartons excessively absorb moisture in the use or storage process and reduce the moisture absorption of the cartons Its compressive strength It is not a single physical index to determine the quality of paper The physical performance of paper should be a comprehensive index Sometimes, in order to prevent the carton enterprises from cutting corners, the carton users put forward requirements for the compression index of the carton, but also put forward excessive weight requirements for the matching of base paper In order to meet the requirements of customers, the carton enterprises only increase the weight of paper and reduce the grade of paper to ensure the cost In fact, considering the comprehensive performance, the corrugated base paper with low weight and high strength is much more stable than the corrugated base paper with low grade and high weight Moreover, the stability of the base paper reduces the differences between the physical properties of the cartons and increases the safety of the cartons, while the paper with low grade and high weight is very stable It's hard to achieve this effect Due to the instability of low grade base paper, it is difficult to accurately estimate the compression resistance in the compression design After the completion of the carton, the physical properties of the individual differ greatly The adulterated inferior products will become the first damage point of Zui in the use or transportation of the carton, which will affect the use of the whole batch of cartons Base paper plays a decisive role in the compression resistance of cartons We need to make some efforts to test and judge all kinds of base paper, and make a reasonable configuration of all kinds of paper to produce cartons that meet the physical performance requirements The carton compression is a comprehensive control process In production, the impact on the carton compression caused by the unreasonable process should be minimized The loss of the carton compression strength is equivalent to the waste of base paper, which is a big hidden waste of Zui, and will inevitably cause a vicious cycle, which will greatly increase the production cost of the carton At the beginning of production, the performance of various base paper is well known Only in actual production can paper be prepared as required.