How to evaluate whether the cartons are up to the standard? Pressure resistance and stacking test

With the development of industry, corrugated box has been widely used as packaging materials Due to the low threshold of corrugated box industry, the competition is extremely fierce In the process of using cartons, users of cartons exposed more or less quality problems, such as the collapse of cartons after stacking, cracking and so on Therefore, more and more carton users have realized the double 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 instruments to evaluate the key indicators of cartons It can withstand breaking and pressure (or stacking), comprehensively study whether the packaging is excessive (material design is excessive), and realize the optimization contribution of packaging material design in the whole product manufacturing cost However, in the process of product inspection, when the carton users evaluate whether the products are qualified, they often have cognitive deviation and misjudge the product test results In the following, how to correctly understand and evaluate the pressure resistance and stacking test of corrugated boxes is analyzed and discussed, and personal practical experience is shared with the carton enterprises and users There are two standards: Inspection state standard and physical index standard Inspection status analysis: the packaging industry usually adopts the inspection status of the following two packaging materials: the temperature and humidity of the carton sample are (23 ± 2) ℃, (50 ± 5)% pretreatment for 24 hours Standard source: Sn / t02693-93 inspection regulation for corrugated box of export commodity transport package The standard atmosphere for testing pulp, paper and paperboard shall be relative humidity (50 ± 2)%, temperature (23 ± 1) ℃, general paper pretreatment for 4h, thin paper for at least 5-8h, high fixed volume or other paper for at least 48h or longer Standard source: GB / t10739-1989 "standard atmosphere for the treatment and test of pulp, paper and paperboard samples" sets the purpose of carton test pretreatment to make the fiber structure of each sample in a balanced and stable state, so as not to make the test results have too big difference and affect the judgment of mechanical properties of the paper box The first pretreatment method shall be used for corrugated boxes Discussion on safety pressure resistance and stacking test Stacking (standard name - static load stacking) is to apply a constant mass to the carton package within a certain time (usually 24 hours), and check whether the deformation and damage of the carton meet the requirements We can intuitively understand their differences through the time chart of test force value: Calculation of formula ① safety anti pressure P = k * g * (H / h-1) * 9.8 P Pressure resistance value n; K Deterioration factor (safety compression factor); G Gross weight of single package kg; H Stacking height M.; H The box height is m the storage period is less than 30 days, 30-100 days and more than 100 days Note that the deterioration coefficient is 1.61.652 The safety compression coefficient of Europe and America is generally adopted for export cartons Note: the deterioration coefficient (strength coefficient) k is determined according to the loaded goods and storage conditions ② stacking quality M0 = k * (H / h-1) * M1 M0 Total stacking mass imposed by carton kg; K Deterioration coefficient (the same as safety compression coefficient); M1 Gross weight of single package kg kg; H Stack height; H Box Height M discussion on relevant issues: the determination of deterioration coefficient implies that under various storage and transportation conditions, the pressure bearing capacity of cartons can not meet the pressure resistance requirements under standard test conditions (for example, the humidity condition is relatively large), but because the coefficient is a safety compression coefficient, its "safety" is to meet the requirements of cartons in: Under different atmospheric conditions, the strength of the container will be reduced; the strength of the transportation and storage will be weakened; the strength of the load stack will be weakened with time; the strength of the transportation vibration and impact will be weakened and the above atmospheric humidity and logistics conditions will not cause the collapse of the container or the bulging deformation to lose the protective effect on the package So as long as the carton is designed and manufactured as qualified (meeting the requirements of safety and pressure resistance), the pressure resistance tested in non-standard state is less than the safety and pressure resistance standard, but it is still "safe" Recognizing this, we can further understand the test differences of cartons in different states through the following example data: comparison item carton model paper match With outer diameter of mm, under different test conditions, pressure resistance test value (kg f), required pressure resistance value (kg f), temperature 18 ℃, humidity 79%, temperature 23 ± 2) ℃, 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 average values In the above table, we can clearly understand that the test results under non-standard conditions with high humidity do not meet the requirements of safety and pressure resistance, but we cannot judge that the products packed in cartons do not meet the standards On the contrary, in the case of small humidity, although the test results meet the requirements, the design and manufacturing are not equal to qualified How to correctly and effectively evaluate whether the test results of carton pressure resistance or stacking meet the standards? Because the results of anti pressure or stacking test have certain equivalence, the analysis of anti pressure can help us better understand Due to the limitations and requirements of test conditions and working efficiency, most manufacturers usually test the pressure resistance of cartons under normal temperature and humidity conditions, and directly evaluate whether the products meet the requirements In fact, there is a great risk of misjudgment in this way of evaluation, which often misleads the evaluation of carton supplier or leads to the loss of carton packaging collapse Under the condition of high humidity in South China, if the non-standard state test pressure strength can meet the safety pressure resistance standard, it means that the carton fully meets the requirements, and the design of the carton meets the requirements; if the tested carton strength fails to meet the safety pressure resistance standard, there are still two possibilities: the carton design and production meet the requirements; The design and manufacture of cartons do not meet the requirements It should be noted that in the case of small humidity conditions in the north, the test results of non-standard state are often higher than the requirements of safety and pressure resistance, but do not mean that they meet the standards Because in the long-distance logistics conditions, especially in the sea transportation conditions, the humidity is large, the test results of non-standard state should consider the factors reflected in the design, otherwise the resulting risks will be difficult to avoid So it is very important to evaluate the result of product test Process and basic methods: to determine the safety and pressure resistance of cartons, and the quality index standard of the code The above two indexes can be obtained by formula, and the determination of the indexes depends on the different domestic and foreign sales and storage periods Under special circumstances, if the carton is supported by contents, the appropriate anti pressure index value can be determined according to the actual situation, and the quality index of the pile code must be determined by the formula Test the pre-treatment state: the carton is pretreated for 24 hours under the standard test state (the general carton users can go to the fair testing agency to test unconditionally) and then retested to make the moisture of the carton reach the dynamic balance state Precautions for sample extraction: in the trial production stage of new products, the strength difference between the sample printing and die-cutting process and the non printing and die-cutting process is about 5-20%, so the state of the sample and the batch products should be basically consistent The sampling of batch products should conform to the principle of statistical probability After years of practical experience, six samples should be selected from three different packages to reduce the risk of misjudgment Result judgment: if one of the carton's anti pressure values tested under the standard state is lower than the anti pressure index, the batch of cartons can be judged as unqualified To improve the efficiency of stacking test: stacking test often takes a long time, and the way of economic and effective evaluation is still in the exploratory stage The following is the experience of discussion and practice by our company and customers Basic principle: the safety anti pressure value of the same box is equal to the stacking quality value, and the low value of the sample anti pressure Zui is not less than the safety anti pressure value By detecting the average value of the anti pressure peak value of six boxes, it can be determined whether the stacking test is qualified We can intuitively understand the relationship between them through the following figure Process and method: we first understand the deviation of the peak pressure resistance of the carton through the empirical test data Under the standard atmospheric conditions: the deviation of the peak pressure resistance of the same double corrugated carton Zui Big Max and Zui small min under the conditions of handling, transportation and storage is about 28 The deviation of single corrugated box is about 33% (individual severely damaged boxes shall be removed) To determine the average value of the standard safety pressure resistance, the average value of the standard safety pressure resistance of double corrugated box shall be 1.15 (15% higher than the safety pressure resistance value), and the average value of the standard safety pressure resistance of single corrugated box shall be 1.18 Detect the peak value of the anti pressure of six sample cartons under the standard state, and calculate the arithmetic mean value of the peak value of the anti pressure of the sample cartons If the arithmetic mean value of the peak value of the anti pressure of the sample cartons is greater than the average value of the standard safety anti pressure, the batch of cartons is qualified, otherwise, they are unqualified The above method has strong operability, which is helpful for improving work efficiency and evaluating stacking test results effectively You may try it Reprinted from: China Packaging Network