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Analysis of Compressive Strength and Influencing Factors of Carton in Jinan Carton Factory
The pressure resistance of a corrugated box is one of the most critical quality indicators in packaging design. During testing, the box is placed between two pressure plates, and the force required to crush it is measured as its pressure resistance, typically expressed in kilonewtons (kN).
First, determining the expected compressive strength of the carton.
Corrugated boxes must have sufficient compressive strength to withstand the weight of stacked boxes during storage and transportation. To ensure this, the compressive strength of the box is calculated using the formula:
P = K × W × (n - 1)
Where:
- P is the compressive strength of the box (in Newtons),
- W is the weight of the loaded box (in Newtons),
- n is the number of stacking layers,
- K is the safety factor based on the storage duration.
The value of n is determined by dividing the total stacking height H by the height of a single box h (n = H/h). The safety factor K varies depending on the storage time:
- For storage less than 30 days, K = 1.6
- For 30–100 days, K = 1.65
- For more than 100 days, K = 2.0
Second, Jinan Carton Factory calculates the compressive strength based on the raw materials. Once the required strength is known, the appropriate corrugated board and paper are selected to produce the box, preventing unnecessary waste. One widely used formula for estimating the compressive strength is the Kellicutt formula, which is particularly effective for 0201 type boxes.
Third, methods for determining the compressive strength.
Due to variations in the production process, the actual compressive strength may differ from estimated values. Therefore, the most accurate way to determine the strength is by conducting a compression test on the finished box under controlled temperature and humidity conditions. For smaller factories without testing equipment, a simple method involves placing a wooden board on top of the box and adding weights to estimate whether the strength meets the requirements.
Fourth, factors affecting the compressive strength of the carton.
1. **Raw Material Quality**: The base paper is the main determinant of the box’s strength, as shown by the Kellicutt formula. However, other production factors such as glue application, impregnation, coating, and lamination also play a role.
2. **Moisture Content**: High moisture levels in the cardboard can reduce its strength. Paper is hygroscopic, so maintaining proper moisture levels is crucial, especially during high-humidity seasons.
3. **Box Design**: The shape and dimensions of the box significantly affect its strength. Double-layer corrugated boxes generally offer better strength compared to single-layer ones. Taller boxes tend to be less stable and weaker.
4. **Printing and Perforation**: Printing or creating openings (like handle holes) can weaken the structure. Large or unevenly placed openings have a more noticeable impact on strength.
5. **Manufacturing Errors**: Issues like incorrect scoring, deep grooves, or weak seams can reduce the box’s pressure resistance.
6. **Dynamic Performance Testing**: For fragile items like glassware or electronics, additional tests such as drop, impact, vibration, and drum rotation are conducted to simulate real-world conditions. These tests help evaluate the cushioning performance and overall durability of the packaging.
These dynamic tests are destructive, but they help improve the packaging’s protective capabilities by incorporating shock-absorbing materials or structural reinforcements. Some boxes may also undergo weather resistance or moisture testing, depending on the client's specifications.