Process design essentials for the bottom-cut corrugated box die-cut blank
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First, the design of the material for the bottom of the corrugated carton
The industrialized production of packaging bottom-cover corrugated boxes for packaging in China started late, and the design theory is very immature. Relevant departments have not yet developed corresponding standards and specifications, which has led designers to grasp the essentials, resulting in unreasonable design of carton size, poor function of carton back cover, excessive paper compression strength, high paper waste, and low productivity of carton production. , high production costs and other issues. However, some countries and regions can grasp the opportunity to quickly develop relevant guidelines and enter the international market, especially in the European and American markets.
1. Cater to the market share of the captain of the corrugated box industry
In order to obtain a large enough sales quota for the corrugated carton of the European market, a large company in a country completely adopted the technical standard of German corrugated paperboard materials (DIN 55468-1987). This standard uses two important data to standardize corrugated paper, that is, t is used to indicate the peak distance of the tile in the paper, and h is used to indicate the height of the tile in the paper. As shown in Figure 1. Taking two data as basic parameters, the corrugated paper was divided into four types (Table 1). According to the paper box (box) designed according to the paper in the table, on the surface, the difference in size may occur depending on the type. In fact, it is more important to cause the difference in the strength of the corrugated box (box). Process designers must be aware that the transverse compressive strength of corrugated board is much less than its longitudinal compressive strength. The four side walls of the common box (box) type which are resistant to compression are vertical corrugated grooves. The bottom corrugated carton (box) is cut into a blank by a piece of cardboard, and the surrounding side is folded and formed at right angles. The four side walls of the carton (box) are vertical corrugated grooves. Therefore, the strength check calculation is applied at design time to apply the Kerikat formula instead of the APM formula.
Process designers should also be aware that the strength of the paper also depends on the strength of the base paper and the number of corrugated layers. The strength of the base paper, Germany is set in other standards. The corrugated layer and the paper used for the bottom corrugated carton (box) are mostly single-slot and double-slot, as shown in Figure 2. Since the volume of corrugated layers more than two layers is significantly increased, a general-purpose back cover carton (box) is rarely used.
2. Based on domestic corrugated paper resources, standardize the design of die-cut blanks
The rapid development of China's corrugated paper industry provides a rich supply of paper for the carton (box) processing industry. Therefore, selecting materials according to market demand and designing die-cut blanks according to specifications is the best way to improve the competitiveness of enterprises in the international market.
The most important thing when designing is to follow the following specification procedures, namely:
2.1 determine the main load during the circulation of the product;
2.2 Calculate the compressive strength of the carton that meets the environmental requirements;
2.3 drawing a structural drawing of the die-cut blank of the bottom corrugated carton (box);
2.4 using the corresponding calculation formula for strength check, mainly to calculate the board strength coefficient S used;
2.5 Check the table to determine the basis weight and type of the base paper.
Second, the three elements of the design process of the bottom of the corrugated carton blank
Industrial machine bonding has extremely high labor productivity. In order to make the high-speed operation smoothly, when designing the die-cut blank, it is necessary to establish which inner edge is used as the reference, that is, the so-called gauge edge. In particular, for cartons that require high precision, tolerance calculations are required as required. Before the machine bonding successfully enters the stacking system (collector), the outer side of the forming box is counted by the side of the folded indentation, and the requirement is not high. That is to say, the design should pay attention to the gauge edge without paying too much attention to others in order to reduce the production cost as much as possible. To this end, the carton forming process design must understand three major elements:
First, the R2 creasing line of the bottom corrugated carton blank cannot be tilted to the left like the image jam (Figure 3). This is the reason for the corrugated groove at the surface of the corrugated paper. If the R2 is tilted, quality problems can occur when the machine is pre-folded and bonded at high speeds - the reference line is frequently offset, the sealing tongue P and the adhesive tongue K are not pleated, and the final formation of the carton does not meet the requirements.
Second, the width of the adhesive tongue K in Figure 2 must be greater than 20 mm, typically up to 40 mm.
Third, due to the die-cutting indentation, the oblique-cutting line Z of the oblique-angled tongue P is an indentation, which is staggered with the cut (long) hole, that is, a certain section of Z1 is an indentation, and the same section of Z2 should be a cut (long). The hole (Fig. 3), so after the beveled tongue P is pleated, it must be pressed against the surface with a large pressing force along the length of Z to enhance the sealing force at the bottom of the carton. In order to ensure the accuracy of this element, and also to simplify the process, the R1 and R3 indentation lines are usually not pre-folded.
Third, grasp the impact of the design of the bottom of the corrugated carton blank on the accuracy of the adhesive box
1. Grasp the bonding precision molding law from the process characteristics of “Zhedezheng”
When the bottom cover corrugated box blank is die-cut, ensure that the indentation line coincides with the corrugated groove. If deviation is expected, it should be offset to the right as far as possible. Generally, the bottom line is deviated to the right with R5 as the reference. Facts have proved that the rightward is better than the left-handed process. After repeated sampling, the R1～R4 lines are coincident with the corrugated groove or slightly to the right, which is opposite to the lining direction of the sealing tongue P, which makes the process become “歪”. The situation is getting right. In this way, the accuracy of the paste box can usually reach ±1.5mm, and the quality of the finished product is high. Therefore, if the process characteristics can be fully grasped at the time of design, the special rules of the corrugated paper back-sealing molding can be ensured, and the high-precision requirements of the adhesive box can be ensured.
2. Grasping the design of the best ratio of height and length of the bottom corrugated carton blank
On the industrialized automatic glue box machine, pre-folding and bonding the bottom cover corrugated paper box, if the whole process of the machine production is to be safe and reliable, the economic operation is smooth, and the carton die-cut blank is not equipped with other auxiliary tools or devices. The height h is always the best ratio to the blank unfolding length c (without the adhesive tongue K). The ratio of the two German corrugated tanks is shown in Table 2:
This optimal ratio is related to the quality of the original paper, the degree of industrialization, and even the environment of the workshop at the time of operation. As a designer, it should be given full attention. In particular, when considering domestic factors, we will consider the many factors to form our own brand design specifications to show our strength.