How to correctly assess whether the carton meets the standard - anti-stress, stacking test

With the development of industry, corrugated cartons have been widely used as packaging materials. Due to the low threshold of the corrugated paper box industry, the competition is extremely fierce. Carton users have exposed more or less quality problems in the use of cartons, such as the collapse, cracking, etc., of cartons after stacking, causing many negative effects.

Therefore, more and more carton users have realized the dual significance of packaging for product protection and product image promotion. Carton users have become more professional and rational in determining product quality standards, such as: Adding test equipment to measure the key indicators of the carton... Breaking and anti-stress (or stacking), comprehensive research whether excessive packaging (material design excess), to achieve packaging The design of the material contributes to the optimization of the entire product manufacturing cost.

However, in the process of product inspection, when the carton user assesses whether the product is qualified or not, it often produces deviations in understanding and misjudging the product test results. The following is a detailed analysis and discussion on how to correctly understand and evaluate the anti-stress and stacking test of corrugated boxes, and share personal practical experience with carton enterprises and users.

Carton anti-pressure, stacking test compliance with the requirements must be clear two standards: test status standards, physical indicators.

Inspection status analysis
The packaging industry usually adopts the following inspection status of two packaging materials:
Carton sample temperature and humidity were (23 ± 2) °C, (50 ± 5)% pretreatment 24h.
Standard Source: SN/T02693-93 "Procedures for the Inspection of Corrugated Carton Containers for Export Goods".
The standard atmosphere for test pulp, paper and board should be relative humidity (50±2)%, temperature (23±1)°C, general paper pretreatment 4h, tissue paper at least 5-8 h, high basis weight or Other paper types At least 48 h or more.

Standard source: GB/T10739-1989 "Standard atmospheres for handling and testing of pulp, paper and paperboard specimens"
The purpose of setting the carton test pretreatment is to make the fibrous tissue structure of each sample in a balanced and stable state, so as not to make the test results produce too large differences and affect the determination of the mechanical properties of the carton. Corrugated boxes should refer to the first type of pretreatment.

Discussion on Safety Anti-pressure and Stacking Test
Conceptual expression
The resistance to pressure is the maximum compressive yield value achieved by a carton that consistently exerts pressure on it.
The stacking code (standard name-static load stacking code) is to apply a constant mass to the carton package within a certain period of time (usually 24 hours), and the amount of deformation and damage caused by the carton is in compliance with the requirements.
We can intuitively understand the difference between them by testing the force time diagram:

Formula Calculation 1 Safety Pressure
P=K*G*(H/h-1)*9.8
P ... pressure resistance value N;
K... deterioration coefficient (safety compression coefficient);
G ... single package gross weight kg;
H... stack height m.;
h ... box height m.
Storage period is less than 30 days 30 to 100 days more than 100 days Remarks coefficient of deterioration 1.6 1.65 2 Export carton is usually used in Europe and the United States the safety factor 3

Note: The coefficient of deterioration (intensity factor) K is determined based on the loaded goods and storage conditions.

2 stacking quality
M0=K* (H/h-1)* M1
M0......the total mass of the stacking pile applied by the carton kgkg;
K...inferior coefficient (with safety factor);
M1...... Single package gross weight kgkg;
H... stack height;
H... box height m.

Related issues:

The determination of the deterioration coefficient implied that under various storage and transportation conditions, the carton pressure capacity cannot meet the pressure resistance requirements under the standard test conditions (if the humidity conditions are relatively large), but because the coefficient is the safety compression coefficient Its "safety" is to meet the carton at:

The reduction of strength under different atmospheric conditions; the strength of handling and warehousing is weakened; the intensity of the load stack decays with time; the intensity of transport vibration shock is weakened, etc. Under the circumstances that the atmospheric humidity and the logistics conditions change, no collapse or bulging deformation is lost. The protective effect of the packaging.

Therefore, as long as the carton is designed and manufactured to be qualified (to meet the requirements of safety and pressure resistance), the anti-pressure tested in the non-standard state is less than the safety and anti-pressure standard, but it is still “safe”. Recognizing this, we can further adopt the following The instance data understands the test differences of the carton under different conditions:

Comparison project
Carton Model Paper Fit Outer Dimensions mm Pressure Test Value (kgf) Pressure Resistance Value (kgf)
Temperature 18°C
Humidity 79% Temperature (23±2)°C
Humidity (50±5)%
M102 A=A 316*260*235 289 342 320
M103 A=A 302*244*235 296 335 305
M106 A=A 502*276*273 321 401 296

Note: The above test values ​​are averages.

In the above table, we can clearly understand that the test results under non-standard conditions with large humidity conditions do not meet the requirements for safety and pressure resistance, but it cannot be judged that the carton packaging products do not meet the standards. Conversely, in the case of relatively small humidity conditions, although the test results meet the requirements, the design and manufacture are not necessarily qualified.

How to correctly and effectively assess whether carton anti-stress or stacking test results meet the standards?
Because of the equivalence of the resistance to pressure or stacking test results, the use of anti-stress analysis can help us understand better.

Due to the limitations and requirements of test conditions and work efficiency, most manufacturers usually test carton pressure resistance under normal temperature and humidity conditions and directly assess whether the product meets the requirements. In fact, the use of this method to assess the existence of a large risk of misjudgment often misleads the cartons supplier in assessing or causing the carton pack to collapse.

In the case of relatively large humidity conditions in the South, if the anti-pressure strength of the non-standard state test can meet the safety and anti-pressure standards, it means that the carton fully meets the requirements, and the design of the carton is in compliance with the requirements; if the tested carton strength is not There are two possibilities for achieving safety and pressure resistance standards:
Carton design and production meet the requirements;
Carton design, production does not meet the requirements.
It should be noted that in the case of low humidity conditions in the north, non-standard state test results are often higher than the safety and compression requirements, but it does not mean that they meet the standards, because in the long-distance logistics conditions, especially the sea conditions are relatively high humidity Non-standard state test results should consider this factor to be reflected in the design, otherwise the resulting risks will be difficult to avoid.

Therefore, it is very important to correctly evaluate the results of product testing.

Process and basic methods:

Determine the carton safety anti-stress, weight quality standards.

Both of the above indicators can be obtained through formulas. The determination of indicators depends on the difference between domestic and foreign sales and storage periods. Under special circumstances, if the carton is supported by contents, the appropriate pressure resistance index value can be determined according to the actual situation. The weight quality index must be determined by the formula.

Check the pretreatment status:

The carton is preconditioned for 24 h under standard test conditions (normal carton users can be tested by an authoritative fair testing agency unconditionally) and then tested again to make the moisture in the carton reach the state of dynamic equilibrium.

Sample extraction notes:

In the trial production phase of new products, the difference between non-printing and die-cut strength after sampling sample printing and die-cutting processes is about 5-20%, so the state of the sample and batch product should be kept basically the same.

The sampling of batch products should meet the principle of statistical probability. After many years of practical experience, the sample sample should be taken from 6 different 3 packages, which can reduce the risk of misjudgment.

The result is judged:

If the carton pressure resistance detected under standard conditions is lower than the pressure resistance index, it can be determined that the batch tank is unqualified.

To improve the efficiency of stacking test: stacking tests often take a long time, and the economic and effective evaluation methods are still in the stage of exploration. The following are the experiences we have discussed and practiced with our customers.

Fundamental:

The pressure value of the same box is equal to the value of the stacking quality. The minimum value of the pressure resistance of the sample is not less than the value of the safety pressure. By checking the average value of the pressure peaks of the 6 boxes, the stacking test can be qualified. . We can intuitively understand their related relationships through the figure below.

Process and method:

We first understand the carton anti-pressure peak deviation through empirical test data under standard atmospheric conditions:

Under the conditions of handling, transportation and warehousing, the maximum double-corrugated cardboard boxes exhibited a maximum deviation from the peak value of the peak Max of approximately 28%, and the single-wall cardboard box had a deviation of approximately 33%. (The individual damaged boxes should be removed.)

Determine the average value of standard safety pressure resistance

The average value of the standard safety pressure against double corrugated cardboard boxes shall normally be 1.15 for safety and pressure resistance (15% higher than the value of safety pressure resistance), and the average safety and pressure resistance for single corrugated cardboard boxes shall be 1.18 for safety and pressure resistance.

In the standard state, the pressure peaks of the six sample carton boxes are detected, and the arithmetic average of the pressure peaks of the sample carton is determined. The arithmetic average of the pressure peaks of the sample carton is greater than the average value of the standard safety pressure, and the batch of carton is qualified. It is not qualified.

The above method has strong operability, which is of great benefit for improving the work efficiency and evaluating the stacking test results more effectively. You may wish to try.

Reprinted from: "Corrugated carton"