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During the use of the cardboard boxes, the main problems that occur are two in number:
1. Puffy or swollen areas;
II. Damage to the cartons.
We analyzed the causes of the problem as follows:
I. The Causes of the Problem
Fat bulge or swelling
Incorrect selection of the frame type
The height of type A is the highest. For the same type of paper, although it has good performance in withstanding vertical pressure, it is not as good at withstanding horizontal pressure as types B and C. After the products are placed in the cardboard box of type A, during transportation, the box will experience lateral and longitudinal vibrations. The repeated impact between the packaging material and the cardboard box causes the cardboard box wall to become thinner, resulting in bulging or swelling.
2. The impact of stacking finished shovel plates
When the products are stored in the finished goods warehouse, they are usually piled up very high, typically reaching two shovel plates high. During the stacking process of the cartons, the strength of the cartons, especially those at the bottom layer, undergoes a "creep" process. This process is characterized by a relatively stable load acting on the cartons for a considerable period of time. Under static load, the cartons will undergo continuous bending deformation. If the static pressure is maintained for a long time, the cartons will collapse and be damaged. Therefore, the bottommost cartons stacked on the shovel plates often bulge and some are crushed. When the cartons are subjected to vertical pressure, the central part of the carton deforms the most, and the crease after the collapse resembles a parabola in an inflated state. Experimental results show that when corrugated cartons are under pressure, the strength at the four corners is the best, and the strength at the midpoint of the cross edge is the worst. Therefore, the feet of the upper shovel plate directly press on the center of the cartons, causing a concentrated load at the center of the cartons, which can lead to the cartons cracking or permanent deformation. Also, due to the wide gaps in the shovel plates, the carton corners may fall in, which will cause the cartons to bulge or become puffed.
3. The exact size of the box height has not been determined.
The height of the cardboard boxes for carbonated beverages and water is generally set as the height of the inner bottles plus about 2mm. Due to the fact that the cardboard boxes are subjected to static loads during stacking and also experience impacts, vibrations, and jolts during transportation, the wall thickness of the boxes becomes thinner, resulting in an additional height. This causes the height of the box to be much greater than the height of the bottle, making the bulging or puffing of the cardboard box more obvious.
The extensive damage to the cartons is mainly due to the following factors:
The size of the cardboard box is improperly designed.
The dimensions of the cardboard box (length, width, and height) are closely related to the box's damage. The size of the box is generally determined based on the number of bottles to be packed and the height of the bottles. The length of the box is the number of bottles in the long direction multiplied by the diameter of the bottle, the width is the number of bottles in the wide direction multiplied by the diameter of the bottle, and the height is basically the height of the bottle. The perimeter of the four sides of the box is equivalent to the entire side wall that supports the pressure load of the cardboard box. Generally, the longer the perimeter, the higher the compressive strength. However, this increase is not proportional. If the perimeter is too large, that is, if there are more bottles inside, the gross weight of the entire box will be larger, and the requirements for the cardboard box will also be higher. It needs to have a higher compressive strength and puncture resistance to ensure the performance of the cardboard box. Otherwise, the cardboard box is more likely to suffer from damage during the circulation process. In the market, the 596mL × 24 bottle pure water box has the greatest damage among all cardboard boxes. This is because it has a large gross weight and is a single-layer kraft paper box, which is prone to damage during the circulation process.
When the length and width of the carton are the same, the height has a significant impact on the compressive strength of the empty carton. When the perimeter of the four sides of the carton remains unchanged, as the height of the carton increases, the compressive strength decreases by approximately 20%.
2. The thickness of the corrugated cardboard does not meet the requirements.
Due to the fact that the corrugated rollers will be worn out during use, the thickness of the corrugated cardboard fails to meet the specified requirements, resulting in a lower compressive strength of the carton and a decrease in the overall strength of the carton.
3. The corrugated deformation of the carton
The corrugated board that causes the corrugation deformation is inherently soft, with low planar strength and low rigidity. The corrugated paper boxes made from such paper boards have low compressive strength and puncture resistance. This is because the shape of the corrugation is directly related to the compressive strength of the corrugated cardboard. The shapes of the corrugation are generally classified as U-shaped, V-shaped, and UV-shaped. The U-shaped type has good extensibility and elasticity, and absorbs more energy. Within the elastic limit, it can still return to its original shape when the pressure is removed, but due to the unstable force points of the circular arcs, the flat pressure strength is not high. The V-shaped type has less contact with the paper surface and poor adhesion, and is more prone to peeling. With the combined force of the two slanted lines, the rigidity is good and the flat pressure strength is large. However, if the external force exceeds the pressure limit it can withstand, the corrugation shape will be damaged and cannot return to its original state when the pressure is removed. The UV-shaped type combines the advantages of the above two types of corrugation, has higher compressive strength, better elasticity and elasticity recovery ability, and is a relatively ideal corrugation type.
4. The number of paperboard layers in the carton is improperly designed.
If the number of cardboard layers is not designed properly, it will lead to an increase in the damage rate of the outer packaging cartons. Therefore, the number of cardboard layers used for the cartons should be considered based on factors such as the weight, nature, stacking height, storage and transportation conditions, and storage time of the packaged goods.
5. The bonding strength of the paper box is poor.
To determine whether the paper box is well bonded, simply tear the bonding surface with your hands. If you find that the original paper surface has been damaged, it indicates that the paper pages are well bonded; if you find that there are no torn fibers or white powder-like paper fibers at the crease bonding area, it means it is a fake bond, which will result in a lower compressive strength of the paper box and affect the overall strength of the entire paper box. The bonding strength of the paper box is related to the grade of the paper, the formulation of the bonding agent, the manufacturing equipment and process operation.
6. The printing design of the cardboard box is unreasonable.
The corrugated shape and structure of the corrugated cardboard determine its load-bearing capacity. Printing can cause certain damage to the corrugated cardboard. The magnitude of the pressure and the size of the bearing area are the main factors affecting the compressive strength of the carton. If the printing pressure is too high, it is easy to crush the corrugation and reduce the corrugation height. Especially when printing at the crease line, in order to perform forced and clear printing at the crease line, the entire cardboard is crushed, causing a significant decrease in the compressive strength of the carton. Therefore, printing at this location should be avoided as much as possible. When the carton is fully printed or has graphics printed on the sides, in addition to the pressure exerted by the embossing roller on the corrugated cardboard, the ink also has an infiltration effect on the surface of the paper, which further reduces the compressive strength of the carton. Generally, when the carton is fully printed, its compressive strength decreases by approximately 40%.
7. The paper usage regulations for the cartons are unreasonable and the paper used does not meet the requirements.
In the past, during the circulation process of goods, they were mainly transported by manpower, with poor storage conditions and mostly in a loose form. Therefore, the puncture resistance and puncturing strength were used as the main criteria for measuring the strength of paper boxes. With the mechanization and containerization of transportation and circulation methods, the compressive strength and stacking strength of paper boxes became the main indicators for evaluating the performance of paper boxes. When designing paper boxes, the compressive strength that the paper boxes can withstand is taken as the condition, and their stacking strength is also tested.
If during the design process of the paper used for the carton, the minimum compressive strength is not taken into account, resulting in the paper used for the carton not reaching the required compressive strength, this will lead to a large number of carton damages. There are clear regulations for the paper weight used for each type of carton, and during the paper replacement process, it is stipulated that only higher specifications can be used, not lower ones.
8. The Impact of Transportation
The reasons for the damage of goods during the circulation process are mostly caused by improper transportation or loading. Even though the packaging protection measures of some products have reached very high standards, they still may suffer damage. The main reasons for this are, apart from unreasonable packaging design, mainly related to the selection of transportation tools and methods. The impact of transportation on the compressive strength of cartons is mainly due to shock, vibration, and jolting. Due to the numerous transportation links, the impact on the cartons is significant. Moreover, the outdated transportation methods, as well as the rough handling and careless dropping by the loaders, all contribute to the likelihood of damage.
9. Poor management of the supplier's warehouse
Due to the short lifespan of the paper box, the corrugated cardboard box will experience a decrease in its compressive strength as the storage time during circulation increases.
Furthermore, the humidity in the warehouse environment also has a significant impact on the strength of the cartons. Cartons have the function of both releasing and absorbing moisture from the environment. When the relative humidity in the warehouse is high, the strength of corrugated cartons will drop sharply.
Often, distributors, due to limited storage space, stack goods very high. Some even pile the goods up to the roof. This has a significant impact on the strength of the cartons. If the compressive strength of the cartons measured according to the standard method is 100%, then applying a 70% static load on the carton will cause it to collapse within one day; a 60% static load will allow the carton to withstand for three weeks; a 50% load will enable it to last for 10 weeks; and a 40% load will allow it to last for more than one year. From this, it can be seen that if the stacking is too high, it will cause fatal damage to the cartons.
II. Measures to Solve the Problem
Measures to address bulging or swelling of cartons:
Determine the corrugated shape of the cardboard box to be the appropriate one.
Among the A-type, C-type, and B-type corrugations, the B-type has the lowest corrugation height. Although its resistance to vertical pressure is poor, it performs best in terms of planar pressure. After using the B-type corrugation for the carton, although the compressive strength of the empty carton will decrease somewhat, the contents have self-supporting properties. During stacking, they can bear a portion of the stacking weight, so the stacking effect of the product is also good. In actual production, different types of corrugations can be selected according to specific circumstances.
2. Improve the storage conditions for products in the warehouse
If the warehouse storage space permits, it is advisable not to stack two pallets high. If it is necessary to stack two pallets high, in order to prevent the concentration of weight during the stacking of finished products, a corrugated cardboard can be inserted in the middle of the stack or flat pallets can be used.
3. Determine the exact size of the cardboard box
In order to reduce bulging or swelling phenomena and achieve a good stacking effect, we set the height of the cartons to be the same as the height of the bottles. This is especially necessary for cartons of carbonated beverages and pure water with relatively higher heights.
Measures to address the issue of damaged cartons:
Design paper boxes with reasonable dimensions
When designing a cardboard box, in addition to considering how to use the least amount of materials while maintaining a certain volume, one should also take into account the size and weight restrictions imposed by the market circulation process on individual cardboard boxes, sales habits, ergonomic principles, and the convenience and rationality of the internal arrangement of the goods. According to ergonomic principles, the appropriate size of the cardboard box shape will not cause fatigue or injury to the human body during operation. Overweight cardboard box packaging will affect the transportation efficiency and increase the probability of damage. According to international trade practices, the weight limit for a single packaging cardboard box is 20kg. In actual sales, for the same product, different packaging methods have different popularity in the market. Therefore, when designing the cardboard box, one should try to determine the size of the packaging based on sales habits.
Therefore, during the design process of the cardboard box, various factors should be taken into consideration. Without increasing the cost or affecting the packaging effectiveness, the compressive strength of the cardboard box should be enhanced. After fully understanding the characteristics of the contents, the appropriate size of the cardboard box should be determined.
2. The corrugated cardboard has reached the specified thickness.
The thickness of corrugated cardboard has a significant impact on the compressive strength of the carton. During the production process, the corrugating rollers wear out severely, resulting in a decrease in the thickness of the corrugated cardboard and a corresponding decline in the compressive strength of the carton. This leads to an increase in the damage rate of the carton.
3. Reduce the deformation of corrugations
Firstly, it is necessary to ensure the quality of the base paper, especially the ring pressure strength and moisture content of the corrugated core paper. Secondly, conduct research on the corrugated paperboard manufacturing process to address the corrugation deformation caused by factors such as the wear of the corrugating rollers and insufficient pressure between the corrugating rollers. Thirdly, improve the paper box manufacturing process by adjusting the gap of the paper feeding rollers of the box-making machine and changing the printing method of the paper box from offset printing to flexographic printing, in order to reduce the deformation of the corrugation. At the same time, attention should also be paid to the transportation of the paper boxes, and try to use container trucks to transport the paper boxes to reduce the deformation caused by the bundling with oil cloth, ropes, and the stepping of loading and unloading workers on the corrugation.
4. Determine the appropriate number of corrugated cardboard layers
Corrugated cardboard can be classified by the number of layers it has as single-layer, three-layer, five-layer, or seven-layer. As the number of layers increases, its compressive strength and stacking strength also increase. Therefore, it can be selected based on the characteristics of the goods, environmental parameters, and consumer requirements.
5. Strengthen the control of the peeling strength of corrugated cartons
The bonding strength between the corrugated core paper of the carton and the surface paper or inner paper can be controlled by using detection instruments. If the peel strength does not meet the standard requirements, the cause should be identified. It is necessary for the supplier to strengthen the inspection of the raw materials for the carton. The tightness and moisture content of the paper must comply with the relevant national standards. And the peel strength required by the national standard can be achieved by improving the quality of the adhesive and modifying the equipment.
6. Design the carton pattern reasonably
Paper boxes should avoid full-page printing and horizontal band printing, especially horizontal printing in the center of the box surface. This is because its effect is similar to that of cross-stitch lines, and the printing pressure will cause the corrugated board to collapse. When designing the printing on the surface of the paper box, the number of color combinations should be minimized. Generally, after single-color printing, the compressive strength of the paper box decreases by 6% - 12%, while after three-color color combination, it will decrease by 17% - 20%.
7. Determine appropriate paper usage regulations
In the specific process of designing paper for cartons, appropriate base paper should be selected. The quality of raw materials is the main factor determining the compressive strength of corrugated cartons. Generally, the compressive strength of corrugated cartons is directly proportional to the basis weight, density, stiffness, and transverse ring pressure strength of the base paper; and inversely proportional to the moisture content. Moreover, the appearance quality of the base paper also cannot be ignored in terms of its impact on the compressive strength of the cartons.
Therefore, to ensure sufficient compressive strength, the first step is to select high-quality raw materials. However, when designing the paper used for the carton, do not blindly increase the weight and grade of the paper, and increase the total weight of the cardboard. In fact, the compressive strength of corrugated cartons depends on the combined effect of the ring compression strength of the face paper and the corrugated core paper. And the corrugated core paper has a greater impact on strength. Therefore, whether from the perspective of strength or economic efficiency, improving the performance of the corrugated core paper grade is more effective than improving the grade of the face paper, and it is much more economical. By visiting the supplier's site for inspection and sampling the raw paper to measure a series of indicators of the raw paper, the use of the carton paper can be controlled well to prevent cutting corners and passing off inferior products as good ones.
8. Improve transportation
Reduce the frequency of goods transportation and handling, adopt the method of local delivery, improve the handling methods (suggestion: use pallets for handling); educate the handlers and improve their quality awareness to prevent rough handling; during vehicle transportation, pay attention to rain and moisture prevention, and ensure that the bundling is not too tight.
9. Strengthen the management of the distributors' warehouses
For the goods sold, the principle of "first in, first out" should be followed. The stacking height should not be too high, and the warehouse should not be too damp. It is necessary to maintain dry and ventilated conditions.
