Back cover corrugated paperboard cutting blanks process design essentials

First, the design of the blanks used for backing corrugated box blanks

In China, the industrialization of carton sealing and corrugated packaging started late, and the design theory is immature. Relevant departments have not yet formulated corresponding standards and specifications, leading designers to lose control of the essentials, resulting in unreasonable carton size design, poor carton back cover function, excessive paper compressive strength resulting in large paper waste, and low productivity in carton production. High production costs. However, some countries and regions can seize the opportunity to rapidly formulate relevant standards and advance into the international market, especially the European and American markets.

1. Meet the standards of the closed-box corrugated cartons industry, compete for market share

A large company in a country has adopted a German corrugated cardboard carton technical standard (DIN 55468-1987) in order to achieve a sufficient sales volume for the European market. This standard uses two important data to regulate the corrugated paper, that is, use t to represent the tile pitch in the paper, and h to indicate the height of the tile trough in the paper. As shown in Figure 1. Taking two data as the basic parameters, the corrugated paper materials are further divided into four types (Table 1). According to the carton (box) designed from the paper in the table, on the surface, there will be differences in the dimensions due to different types. In fact, it is more important that the difference in the strength of corrugated boxes (boxes) will be caused. Process designers must clearly know that the lateral compressive strength of corrugated cardboard is far less than its longitudinal compressive strength. The four side walls of the common box (box) type that resist compression are vertical corrugations. The back cover corrugated paper box (box) is die-cut from one piece of paperboard into blanks and folded around at right angles. The four side walls of the carton (box) are vertical corrugated grooves. Therefore, the strength calibration calculation is applied at the time of design using the Kailimate formula instead of the APM formula.

Process designers should also be aware that the strength of the paper material also depends on the strength of the base paper and the number of corrugated layers. The strength of the base paper is set by Germany in other standards. The number of corrugated layers and backing corrugated cartons (boxes) are mostly single-slot and double-slot, as shown in Figure 2. Because the volume of paper with more than two layers of corrugated layers is significantly increased, the universal bottom-end carton (box) is rarely used.

2. Based on domestic corrugated paper resources, standard die-cutting blank process design

The rapid development of corrugated paper industry in China provides a rich paper supply 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 increase the competitiveness of enterprises in the international market.

When designing, the most important thing is to follow the following normative procedures:

1 determine the main load in the process of product circulation;

2 Calculate the compressive strength of the carton that meets the environmental requirements;

(3) drawing a diagram of the die cut blank of the backing corrugated box (box);

4 to use the corresponding calculation formula for strength check, mainly to calculate the use of cardboard strength factor S;

5 check the table to determine the quantitative paper, 楞 type.

Second, the three major elements of the blank box blank blank molding process design

Industrial machine adhesive molding has a very high labor productivity. In order to allow high-speed operation to proceed smoothly, when designing a die-cut blank, it is established which inner edge is used as the reference, that is, the so-called gauge edge. In particular, the carton requiring higher precision requires tolerance calculations as required. Before the machine is successfully bonded into the stacking system (collector), the outside of the forming box is counted along the folded-indented edge. The requirement is not high. That is, design should pay attention to the distance from the regulation without paying too much attention to others, in order to reduce production costs as much as possible. For this reason, the carton forming process design must understand three major elements:

One is that the R2 indentation line of the blank corrugated carton blank cannot be tilted to the left as in the case of an imaging jam (Figure 3). This is due to corrugated grooves in the corrugated surface. If R2 is tilted, quality problems occur at high speed pre-folding and bonding of the machine—frequent deviation of the reference line, falsification of the backing tongue P and adhesive tongue K, and final shaping of the carton do not meet the requirements.

The second is that the width of the bonding tongue K in Figure 2 must be greater than 20 mm, and generally 40 mm.

The third reason is that the zigzag indentation bevel tongue P is the indentation of the zigzag line Z and is staggered with the cut (long) hole. That is, a section of Z1 is indented, and the same section of Z2 should be cut (long). The hole (Figure 3), so after the beveled tongue P is pleated, the surface must be pressed along the length of Z with a large compressive force over the surface to enhance the sealing force at the bottom of the carton. In order to ensure the exactness of this element and also to simplify the process, the R1 and R3 indentation lines are not pre-folded.

Third, to grasp the effect of the blank box blank design on the precision of the adhesive box

1. Grasp the accuracy of the bonding process from the process characteristics

When the backing blank corrugated cardboard blank is die-cut, the indentation line should be overlapped with the corrugation trough. If it is expected that deviation will occur, it should be shifted to the right as much as possible. Generally, the bottom line is deviated to the right with reference to R5. Facts have proved that the right-hand side is better than the left-hand workmanship. After multiple sampling tests, the R1～R4 lines coincide with the corrugated groove or slightly to the right, which is opposite to the fold-back direction of the back cover tongue P, resulting in the formation of the process. The situation is correct. In this way, the accuracy of the gluing cassette can 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, following the unique laws of the molding of the corrugated cardboard backing, it can be ensured that the viscous cassette can meet the high precision requirements.

2. Grasp the design of the optimal ratio of the height and length of the blank of the backing and corrugated box

On industrialized automatic glue sticking machines, pre-folded and glued back-bottom corrugated boxes, to ensure that the whole process of machine production is safe, reliable, economical and smooth, without the need for other auxiliary appliances or devices, the carton die cut blanks The height h and the blank development length c (without the adhesive tongue K) always have the best ratio. The ratio of the two German corrugated tanks is shown in Table 2:

This optimum ratio is related to the quality of the base paper, the degree of industrialization, and even the environment of the workshop when it is operated. As a designer, it should pay full attention to it. In particular, when considering the use of domestic paper materials, a number of factors were taken into consideration to form a design specification of its own brand to show its strength.

Li Guohui

Reprinted from: Guangdong Printing - 2005 Issue 4