Deformation detection Deformation testing should not be overlooked because deformed corrugated cardboard may seize paper production equipment. Some distortions are negligible. Previously in the industry, it was agreed that a one-fourth inch deformation in 24 inches could still be tolerated. However, increasing standards in the industry are becoming more and more stringent, requiring that the warping distortion within 24 inches should not be greater than 1 in 16 inches. The deformation conditions include upturned, downturned, edge-to-edge curling, twisted deformation, and S-shaped deformation, and the causes are various, which will cause adverse effects on the production of the carton.
The most common cause of deformation is the difference in the humidity of the raw materials used to produce the corrugated board. If the top linerboard and the bottom linerboard have different moisture contents, deformation may occur at any time due to the different shrinkage and expansion of the paper fibers. Some of the variable factors in the production of corrugated paper, such as adhesive formulations and amounts, heated metal sheets, preheater temperatures, the use of water and water vapor, roll paper forces, etc., may cause deformation of the corrugated board. The angle of the paper fibers, in particular the different fiber angles between the lower linerboards, can also cause the corrugations to deform. Different substrates, coating materials and other raw materials will also become deformation factors. When dealing with deformation problems, you must monitor the nature of the paper and the equipment process.
Washboard Phenomenon A common problem encountered in the detection of corrugated board printing is the “washboard phenomenonâ€, which is caused by the sagging of the upper liner between the corrugated paper domes, resulting in a change in the thickness of the corrugated cardboard. This has a great influence on the printing. In the flexographic printing, there will be a blank printing phenomenon, causing serious printing quality problems for the printed barcode. In order to solve this problem, many press operators tend to increase the printing pressure, but this will seriously reduce the strength of the carton.
The root cause of the washboard phenomenon is on corrugated board production equipment, so it is often necessary to adjust the amount of adhesive. However, factors such as the basic weight of the paper, the number of blowholes, and the direction of the fibers may also be the cause of the washboard phenomenon.
Printability and Adhesion Absorption To obtain the best print quality for corrugated board, the substrate must match the ink and allow the ink to adhere to the surface of the corrugated board. The interaction between the ink and the substrate is of great significance. The following tests are generally considered to be paper inspections and have an important role to play in printing businesses that encounter printing problems or are trying to improve the quality of graphics. Since inks and corrugated adhesives are usually water-soluble, these tests are also very useful in assessing the degree of bonding. They are porosity detection, normality detection, and permeability/absorbency detection.
Porosity testing
The porosity of the substrate has a very important role in ink coating. If the porosity of the substrate is too high, ink or adhesive can penetrate into the interior of the paper. If the porosity does not meet the requirements, the adhesive will not fully function. The porosity is an indirect parameter that reflects the paper density, aperture size, and paper smoothness.
Smoothness detection If the smoothness does not meet the requirements, it will cause rough printing quality problems, graphic edges blurred, or flashing. The smooth paper surface facilitates adhesive bonding. Caseboard paper surface smoothness testing includes the following:
* EMVICO smoothness detection (mechanical stylus detection)
* Bendtsen Smoothness Detection* Parker Print Surface Inspection These tests are all standard tests. Most paper mills need to provide test data.
In order to obtain excellent print quality with very clear graphics, permeability testing should prevent the ink from penetrating into the interior of the paper or spreading around it, otherwise a burr phenomenon will occur. The ink should adhere to the surface of the paper. In addition, ink consumption should be reduced as much as possible in order to reduce costs and shorten drying time.
Paper Detection The following paper tests are used to predict carton packaging performance. Composite board inspections can indicate how the corrugated board performance is, or whether there is a problem with corrugating, and the following paper tests are used to select papers specifically required for the cartons. They are basic weight detection, STFI detection (also called "short-time compression detection") and ring pressure detection.
Basic weight detection This is the minimum inspection. The basic weight is the weight per unit area of ​​paper. The universal metering weight for cardboard boxes in the United States is how many pounds per thousand square feet. The basic weight of linerboard is 35 pounds per thousand square feet, 42 pounds and 69 pounds. The basic weight of corrugated paper is generally 26 pounds per 1,000 square feet and 33 pounds. As the basic weight increases, the strength of paper and composite board increases accordingly.
STFI and the ring pressure test carton manufacturer are very concerned about the lateral strength of the paper, because the lateral strength of the paper in the corrugated cardboard will eventually be reflected in the compressive strength. STFI or ring pressure tests are usually indispensable for paper detection. According to the existing formulae, the STFI and ring pressure detection values ​​can be converted to edge compression strength detection values. In other words, in the case of mastering the STFI or the value of the ring pressure detection, the relevant formula can be used to predict the edge compression strength and calculate the carton compressive strength. Listed below are general formulas for edge compression strength. Since the formula does not list the calculation constants, it cannot be used to predict the edge compression strength based on the known ring crush strength or STFI calculation results. This formula is only illustrative.
BCT (edge ​​compression strength) = (DB intensity) + (SF intensity) + (A*Med intensity).
* (DB strength) = double-sided board paper ring pressure or STFI value * (SF strength) = single-side board paper ring pressure or STFI value * (Med strength) = corrugating medium ring pressure or STFI value * A = corrugated base paper Extension factor The extension factor relates to the amount of corrugated base paper that is additionally used for corrugation. For C grade corrugated paper, the coefficient is about 1.43. The ring pressure value is often expressed as 1bf/6 inches because the sample length is 6 inches. In this case, the ring pressure must be divided by 6.
In the production process, other factors will also affect the strength of the finished corrugated board. Therefore, ECT inspection is also required when corrugated board is removed from corrugated paper production equipment. If there is a large difference between the predicted ECT value and the measured ECT value, it may indicate that there may be some abnormalities in the tile paper production equipment.
It may be boring and practical to spend a lot of time on the actual application to talk about the detection process. However, all the above tests can help cartons manufacturers to produce cartons at the lowest cost to meet their actual needs. If the customer wants to use a carton with an ECT value of 32 pounds, the carton structure you use is 42-26-42. If the carton does not meet the strength requirements, two treatments are available. One is to increase the basic weight of the linerboard, but the total weight and cost will increase, and it is impossible to be sure that the strength meets the predetermined requirements before the ECT inspection is performed; the second is to find the STFI or the ring pressure value meet the predetermined requirements. The paper material, after testing, proved to be used to produce corrugated cardboard whose strength was up to the standard of use, and then to purchase heavier container board paper and prototype the corresponding corrugated cardboard samples on the corrugated paper machine. The above tests can save time, raw materials and costs for carton manufacturers.
Mckee Corporation and carton strength prediction In the 1960s, Dr. McKee of the Paper Science and Technology Association proposed a formula to predict the compressive strength of corrugated boxes using edge compression strength values, flexural strength values, and carton perimeter values, McKee The formula enables carton manufacturers to predict the overall carton packing performance based on individual strength values.
The specific expression of the Mckee formula is:
Carton compressive strength prediction (BCT) = 2.028 × ECT 0.746 × (DXDY) 0.127 × P 0.492, where ECT is the edge compression strength (in pounds per square inch) and DXDY is the geometric mean of the compressive strength (in pounds inch). ), P is the perimeter of the carton (inches).
In Mckee's simplified formula, the thickness is used to replace the bending strength:
BCT = 4.87 x ECT x Caliper 0.508 x P 0.492, where ECTJ is the edge compression strength value in pounds per square inch, Caliper is the cardboard thickness in inches, and P is the circumference of the carton in inches.
Carton manufacturers can use the above simplified formula to quickly calculate the compressive strength of the carton. For this purpose, as long as the edge compression strength test is performed, the thickness of the cardboard is measured and the carton perimeter can be calculated. Or before the production of corrugated paper and carton, calculate the ECT value according to the STFI or the ring pressure value to determine the compressive strength of the carton. (End) [United States] Matt Coleman, Mike Sherpa
The most common cause of deformation is the difference in the humidity of the raw materials used to produce the corrugated board. If the top linerboard and the bottom linerboard have different moisture contents, deformation may occur at any time due to the different shrinkage and expansion of the paper fibers. Some of the variable factors in the production of corrugated paper, such as adhesive formulations and amounts, heated metal sheets, preheater temperatures, the use of water and water vapor, roll paper forces, etc., may cause deformation of the corrugated board. The angle of the paper fibers, in particular the different fiber angles between the lower linerboards, can also cause the corrugations to deform. Different substrates, coating materials and other raw materials will also become deformation factors. When dealing with deformation problems, you must monitor the nature of the paper and the equipment process.
Washboard Phenomenon A common problem encountered in the detection of corrugated board printing is the “washboard phenomenonâ€, which is caused by the sagging of the upper liner between the corrugated paper domes, resulting in a change in the thickness of the corrugated cardboard. This has a great influence on the printing. In the flexographic printing, there will be a blank printing phenomenon, causing serious printing quality problems for the printed barcode. In order to solve this problem, many press operators tend to increase the printing pressure, but this will seriously reduce the strength of the carton.
The root cause of the washboard phenomenon is on corrugated board production equipment, so it is often necessary to adjust the amount of adhesive. However, factors such as the basic weight of the paper, the number of blowholes, and the direction of the fibers may also be the cause of the washboard phenomenon.
Printability and Adhesion Absorption To obtain the best print quality for corrugated board, the substrate must match the ink and allow the ink to adhere to the surface of the corrugated board. The interaction between the ink and the substrate is of great significance. The following tests are generally considered to be paper inspections and have an important role to play in printing businesses that encounter printing problems or are trying to improve the quality of graphics. Since inks and corrugated adhesives are usually water-soluble, these tests are also very useful in assessing the degree of bonding. They are porosity detection, normality detection, and permeability/absorbency detection.
Porosity testing
The porosity of the substrate has a very important role in ink coating. If the porosity of the substrate is too high, ink or adhesive can penetrate into the interior of the paper. If the porosity does not meet the requirements, the adhesive will not fully function. The porosity is an indirect parameter that reflects the paper density, aperture size, and paper smoothness.
Smoothness detection If the smoothness does not meet the requirements, it will cause rough printing quality problems, graphic edges blurred, or flashing. The smooth paper surface facilitates adhesive bonding. Caseboard paper surface smoothness testing includes the following:
* EMVICO smoothness detection (mechanical stylus detection)
* Bendtsen Smoothness Detection* Parker Print Surface Inspection These tests are all standard tests. Most paper mills need to provide test data.
In order to obtain excellent print quality with very clear graphics, permeability testing should prevent the ink from penetrating into the interior of the paper or spreading around it, otherwise a burr phenomenon will occur. The ink should adhere to the surface of the paper. In addition, ink consumption should be reduced as much as possible in order to reduce costs and shorten drying time.
Paper Detection The following paper tests are used to predict carton packaging performance. Composite board inspections can indicate how the corrugated board performance is, or whether there is a problem with corrugating, and the following paper tests are used to select papers specifically required for the cartons. They are basic weight detection, STFI detection (also called "short-time compression detection") and ring pressure detection.
Basic weight detection This is the minimum inspection. The basic weight is the weight per unit area of ​​paper. The universal metering weight for cardboard boxes in the United States is how many pounds per thousand square feet. The basic weight of linerboard is 35 pounds per thousand square feet, 42 pounds and 69 pounds. The basic weight of corrugated paper is generally 26 pounds per 1,000 square feet and 33 pounds. As the basic weight increases, the strength of paper and composite board increases accordingly.
STFI and the ring pressure test carton manufacturer are very concerned about the lateral strength of the paper, because the lateral strength of the paper in the corrugated cardboard will eventually be reflected in the compressive strength. STFI or ring pressure tests are usually indispensable for paper detection. According to the existing formulae, the STFI and ring pressure detection values ​​can be converted to edge compression strength detection values. In other words, in the case of mastering the STFI or the value of the ring pressure detection, the relevant formula can be used to predict the edge compression strength and calculate the carton compressive strength. Listed below are general formulas for edge compression strength. Since the formula does not list the calculation constants, it cannot be used to predict the edge compression strength based on the known ring crush strength or STFI calculation results. This formula is only illustrative.
BCT (edge ​​compression strength) = (DB intensity) + (SF intensity) + (A*Med intensity).
* (DB strength) = double-sided board paper ring pressure or STFI value * (SF strength) = single-side board paper ring pressure or STFI value * (Med strength) = corrugating medium ring pressure or STFI value * A = corrugated base paper Extension factor The extension factor relates to the amount of corrugated base paper that is additionally used for corrugation. For C grade corrugated paper, the coefficient is about 1.43. The ring pressure value is often expressed as 1bf/6 inches because the sample length is 6 inches. In this case, the ring pressure must be divided by 6.
In the production process, other factors will also affect the strength of the finished corrugated board. Therefore, ECT inspection is also required when corrugated board is removed from corrugated paper production equipment. If there is a large difference between the predicted ECT value and the measured ECT value, it may indicate that there may be some abnormalities in the tile paper production equipment.
It may be boring and practical to spend a lot of time on the actual application to talk about the detection process. However, all the above tests can help cartons manufacturers to produce cartons at the lowest cost to meet their actual needs. If the customer wants to use a carton with an ECT value of 32 pounds, the carton structure you use is 42-26-42. If the carton does not meet the strength requirements, two treatments are available. One is to increase the basic weight of the linerboard, but the total weight and cost will increase, and it is impossible to be sure that the strength meets the predetermined requirements before the ECT inspection is performed; the second is to find the STFI or the ring pressure value meet the predetermined requirements. The paper material, after testing, proved to be used to produce corrugated cardboard whose strength was up to the standard of use, and then to purchase heavier container board paper and prototype the corresponding corrugated cardboard samples on the corrugated paper machine. The above tests can save time, raw materials and costs for carton manufacturers.
Mckee Corporation and carton strength prediction In the 1960s, Dr. McKee of the Paper Science and Technology Association proposed a formula to predict the compressive strength of corrugated boxes using edge compression strength values, flexural strength values, and carton perimeter values, McKee The formula enables carton manufacturers to predict the overall carton packing performance based on individual strength values.
The specific expression of the Mckee formula is:
Carton compressive strength prediction (BCT) = 2.028 × ECT 0.746 × (DXDY) 0.127 × P 0.492, where ECT is the edge compression strength (in pounds per square inch) and DXDY is the geometric mean of the compressive strength (in pounds inch). ), P is the perimeter of the carton (inches).
In Mckee's simplified formula, the thickness is used to replace the bending strength:
BCT = 4.87 x ECT x Caliper 0.508 x P 0.492, where ECTJ is the edge compression strength value in pounds per square inch, Caliper is the cardboard thickness in inches, and P is the circumference of the carton in inches.
Carton manufacturers can use the above simplified formula to quickly calculate the compressive strength of the carton. For this purpose, as long as the edge compression strength test is performed, the thickness of the cardboard is measured and the carton perimeter can be calculated. Or before the production of corrugated paper and carton, calculate the ECT value according to the STFI or the ring pressure value to determine the compressive strength of the carton. (End) [United States] Matt Coleman, Mike Sherpa
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