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The compressive strength of corrugated boxes and design methods

determination of carton packaging elements

when designing commodity packaging cartons, designers first encounter these problems:

1 How much is the quantity of goods in a carton and the weight of a single carton? How to determine

2. Based on what to determine the internal arrangement of carton products, how to choose the best arrangement

3. The specific method designed is: let the faulty instrument and the normal instrument operate under the same conditions. The box length can carry out in-situ dynamic inspection of materials by adding high-speed camera device, dynamic C-scan device and X-ray camera device at the same time of impact test. Is the width and height dimension conducive to enhancing the strength of cartons and saving raw materials

the quantity, weight, arrangement of products in the carton, the internal and external dimensions of the carton, as well as the specifications of corrugated cardboard materials and other factors are the primary considerations, because they ultimately determine the manufacturing, accommodation, storage and transportation of the packaging carton, and whether the lifting action of the lower jaw seat is consistent with the words shown on the button, which is the efficiency, economy and overall function of use

single box weight

according to international trade practices, the single box weight of corrugated boxes used as transportation packages for consumer goods is generally not more than 20 kg, with a maximum of 25 kg. Mainly considering the convenient operation of porters or clerks, it is not easy to cause human injury and other factors. China's national standards, for example, stipulate that the maximum weight of a single packing box handled manually is 18 kg. Therefore, it is reasonable to limit the weight of corrugated box goods of general consumer goods to 20 kg

of course, the cushioning transportation packaging cartons of large and medium-sized industrial products should not be subject to this restriction

the net weight of packaged goods can be calculated by multiplying the number of products inside by the unit weight of the product. Of course, the weight (gross weight) of the whole carton also includes the weight (tare weight) of the carton's own materials and lining materials

it should be noted that according to trade practices, the weight of a single box should not be greater than 20 kg. However, if the weight of a single carton is too small, it is unwise, because small cartons contain a small number of products, the relative consumption rate of materials is high, and the manufacturing process is similar to that of large cartons. The overall efficiency of the production, use and packaging of small cartons is not as good as that of large cartons. Therefore, as long as possible, it should be close to 20kg as much as possible to give full play to its function

quantity of contents

the quantity of products in cartons is mainly calculated and determined by dividing the maximum allowable weight of cartons by the unit weight of products

since the arrangement of the length, width and height of the internal products (which determines the overall size of the carton), the number of contents is not optional or determinable. Generally, several different quantity schemes can be considered in the design, and then determined according to the principle that not only meets the weight limit, but also facilitates the flexible adjustment of the arrangement

specifically, the number of items inside should choose a value with more decomposition factors, which is conducive to the adjustment of length, width and height. For example, 7, 11, 13, 17, 19, 23, 29, 41, 43, 47 should not be selected, because these number decomposition factors only have 1 and itself, and there is no other more permutation. On the contrary, if 12 pieces are selected, 12=1223, there are 1211, 621, 431, 341, 322, 612 and many other available length width height arrangements. If you choose 10 pieces, 10=125, the available length width height arrangement is much less than 12. Therefore, between several values that do not differ much, the value with more decomposable factors should generally be selected. The traditional combination of commodity quantity in the market is more than 12 (a dozen) or its multiples, which is obviously conducive to the modularization and standardization of circulation links

arrangement of contents

refers to the specific arrangement number of products in three directions of length, width and height inside the carton

in fact, the internal arrangement of the product has been taken into account when determining the number of contents. In addition to the choice of number, it also involves the structural strength and material consumption of cartons

when arranging in the direction of length, width and height, first of all, it should be considered that the external dimension of the box should conform to the limit obtained according to the ergonomic principle

according to the carton strength test, under the same peripheral length, the length width ratio of corrugated carton is between 1.2 ~ 1.6, and its compressive strength is the best. Under the same comprehensive size (the sum of length, width and height), the compressive strength decreases with the increase of the height of the corrugated box, because the stacking load is mainly distributed on the vertical box plate

in fact, when the box type with top opening is adopted, there is little choice of size in the height direction. Because the more layers of products, the higher the box height, which is not convenient for taking things, but also not conducive to ensuring sufficient compressive strength

but if the height is too small, it also has a negative effect. At this time, the ratio of the material used for the non bearing surface (top and bottom) to the material used for bearing the vertical box surface is higher than that of the box with larger height, so the efficiency utilization rate of the carton material is poor. According to the unfolding diagram of 0200 box blank, the relative material consumption rate of cartons with small height under the same volume is large

external dimensions of the box

in addition to the transportation boxes of special shapes or large industrial products, human intervention is inevitable in the transportation and handling of corrugated boxes for general goods. Many consumer goods also need to be handled or unpacked by clerks in the process of entering the store and putting on the cabinet. If the external dimension of the carton is unreasonable and the hug space is too large, it will make the arms and waist tense and it will be difficult to walk, which will lead to operation fatigue or damage. Japanese scholars have done experiments on the handling of carton goods with different weights and sizes. By measuring the indexes of the human body such as the central lung and muscle during the handling process, the changes in the working efficiency and fatigue limit of the human body are calculated, so as to obtain the overall dimensions of the box in line with the ergonomic principles

the length dimension, length plus width dimension, and the comprehensive dimension of length, width and height of general cargo cartons should be limited as follows:

the specific calculation method of corrugated carton size is introduced below

the maximum dimension Xi in the box (in a certain direction) can be obtained by multiplying the maximum external dimension (in a certain direction) of a single product by the number of permutations in this direction, plus the thickness of gasket material, product gap tolerance, etc

xi= xmax n + D (n-1) + T + ki

xmax is the maximum external dimension of a single piece of interior

n is the product arrangement quantity

d is the tolerance (or gap) between the inner products (1mm/piece for small boxes, 2mm/piece for medium boxes, 3mm/piece for soft articles, and +2mm/piece for hard articles)

t is the sum of the thickness of the product spacer or liner material

ki is the internal dimension correction coefficient (5 for L direction, 5 for B direction, and 2 for H direction: small box, 4 for medium box, and 6 for large box)

carton manufacturing dimension x is the dimension to be used for die cutting and pressing line during manufacturing, that is, the dimension marked on the box blank expansion drawing. It is formed by the inner size plus the thickness of corrugated board, plus a certain correction number. The correction number of manufacturing dimension in the length and width direction has two values respectively, because the thickness of the overlapped (nailed or glued) part of the box wall increases when the box blank is folded, but the geometric squareness of the box space after forming must be guaranteed

x = Xi + km

km is the manufacturing dimension correction, which is related to the thickness of corrugated board, that is, the thickness of corrugated board plus a tolerance, as shown in Table 1

Table 1 manufacturing dimension coefficient of 0200 corrugated boxes

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