Packaging Quality Issue & Solutions XVII

答：

After the corrugated cardboard boxes are stacked in multiple layers in the warehouse, the bottom boxes deform, bulge or even collapse, unable to withstand the long-term static pressure from the goods above. The compressive strength is the core indicator of the cardboard box's carrying capacity, while the actual stacking strength is usually only 40% to 60% of the short-term compressive strength.

Solution：

• Paper box compressive strength test: Using a paper box compressive strength testing machine, in accordance with GB/T 4857.4, apply vertical pressure to the intact paper box at a speed of 10 ± 3 mm/min, and record the maximum compressive load and deformation curve.
• Static load stacking test: Using a stacking test machine, calculate the load based on the actual stacking layers (F = (n - 1) × W), apply constant pressure for more than 24 hours, and measure the permanent deformation rate after unloading (the height loss is usually required to be ≤ 5% - 10%).The box compression test and static load stack test can be conducted by the box compression tester (https://www.linktesting.org/884.html/carton-compression-tester-kyj-10k/)

Edge pressure strength (ECT) test: Using an edge pressure strength testing machine, in accordance with GB/T 6546-2021, cut a 100mm × 25mm sample along the corrugated direction and apply pressure, determine the edge pressure strength (kN/m), which is a material-level basic indicator for predicting the compressive strength of the paper box. The test can be conducted by the paper crush tester（https://www.linktesting.org/5407.html/paper-crush-tester-hsd-01a/）

答：

During the processes of manual handling, sorting and loading, the cartons may fall or be thrown, resulting in cracks on the edges of the cartons, cracks in the seals or failure of the buffers, which causes damage to the contents inside. The impact of the fall is one of the main causes of carton damage in the logistics process.

Solution：

• Drop test (surface/edge/angle): Using a single-wing or double-wing drop testing machine, in accordance with GB/T 4857.5, lift the carton to the set height (such as 0.5m, 1.0m, 1.5m), and conduct face drop, edge drop and corner drop tests respectively. After the test, check the degree of damage to the box and the integrity of the contents inside.
• Critical drop height determination: Gradually increase the drop height until the carton shows functional damage (such as damage to the contents or a through break in the box), and determine the critical drop height of this packaging design to provide a basis for matching with logistics The drop test and height determination test can be conducted by the drop tester(https://www.linktesting.org/9506.html/single-wing-drop-tester-dlj-01/)

答：

When the carton is subjected to local concentrated compression during stacking or transportation, the paperboard will rupture before reaching its compressive limit. Bursting strength reflects the ability of cardboard to resist uniform vertical pressure until it breaks, and it is an important mechanical index for evaluating the resistance of cardboard to external impact and compression.

Solution:

• Bursting strength test: Use a bursting strength Tester (Mullen Tester). According to GB/T 6545 or GB/T 1539, hold the sample in a ring fixture and apply hydraulic pressure at a rate of 170±15 mL/min until the sample breaks. Record the maximum pressure value (kPa). At least 10 valid samples need to be tested and the average value is taken.
• Bursting strength calculation: Divide the bursting strength by the basis weight of the cardboard (g/m²) to obtain the bursting strength index (kPa·m²/g), which is used to compare the material properties of different batches or different suppliers of cardboard after eliminating the difference in grammage.

Environmental condition control: The sample needs to be balanced in a standard environment of 23 ± 1℃ and 50 ± 2%RH for at least 4 hours. For every 1% increase in humidity, the tear strength may decrease by 0.5% to 1.2%. Therefore, the temperature and humidity records during the test are crucial. The bursting strength test can be conducted by the burst tester(https://www.linktesting.org/1351.html/full-automatic-bursting-strength-tester-npd-1000s/)

答：

After the corrugated cardboard box undergoes printing, grooving and edge stapling, there is a deviation in the box size from the designed value. The lid may not close tightly or there will be excessive gaps after closing, which affects the sealing quality and stacking stability of the box. The fluctuation in paperboard weight and thickness is one of the fundamental reasons for the instability of the cutting/slicing dimensions.

Solution:

• Paperboard density measurement: Use a circular sampling device and an electronic balance (with an accuracy of 0.001g). According to GB/T 451.2, take a 100 cm² sample and weigh it to calculate the density (g/m²). If the density deviation is too large, it will cause inconsistent compression amounts of the paperboard under the same pressure, thereby affecting the stability of the creasing depth and slotting size.The circular sampler can choose the (https://www.linktesting.org/1203.html/circle-sample-cutter-lt-sc/)
• Paperboard thickness measurement: Use a digital thickness tester (with an accuracy of ±0.1 μm or micrometer level), measure the thickness at multiple points on the paperboard. The thickness fluctuation of corrugated paperboard will directly change the actual pressing depth of the creasing wheel, resulting in inconsistent creasing depth and a deviation in the closing angle of the lid after folding.The thickness test can be conducted by the thickness tester (https://www.linktesting.org/920.html/thickness-tester-ltchy-hs/)

Verification of creasing depth and folding angle: After slotting and creasing, fold the actual paper box and measure the width of the gap after the lid closes. Based on the density and thickness data, infer the reasonable setting range of creasing wheel pressure and depth, forming a correspondence between process parameters and incoming material fluctuations

答：

When the carton is subjected to impacts from the teeth of forklifts, the edges of pallets, or the sharp corners of other goods during loading, stacking or transportation, the paperboard is instantly punctured, forming holes, which causes the contents inside to be exposed or damaged. The puncturing strength reflects the ability of the paperboard to resist penetration by sharp objects under dynamic impact loads, and it is different from the static burst strength which reflects the force application method.

Solution:

• Puncture strength determination: Using a puncture strength tester, in accordance with GB/T 2679.7, hold the paperboard sample in the fixture, release the pendulum with a triangular puncture head to impact the sample, and record the force value (F) consumed to penetrate the sample, which is the puncture strength.The test can be conducted by the customized tensile tester (https://www.linktesting.org/7007.html/automatic-tensile-tester-xlw-500n/)
• Multi-directional sampling test: Cut samples from the front, back, and longitudinal and transverse sides of the paperboard. Test at least several valid samples in each direction to calculate the average value and evaluate the consistency of the paperboard's puncture resistance in different directions.

Range selection and calibration: Select an appropriate weight hammer based on the estimated strength, so that the test reading falls within 20% to 80% of the range to ensure accuracy; perform zero-point calibration and friction compensation before the test