Key points of process design for die cutting blank

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Key points of process design for die-cutting blanks of back cover corrugated cartons

I. design of materials for back cover corrugated cartons

the industrialization of back cover corrugated cartons for packaging in China started late, and the design theory is very immature. The relevant departments have not formulated the corresponding standards and specifications, which leads to the designers' inability to grasp the essentials, resulting in unreasonable carton size design, poor carton back cover function, excessive carton compressive strength, resulting in large waste of paper, low productivity of carton production, and high production costs. However, some countries and regions can seize the opportunity to quickly formulate relevant standards and enter the international market, especially the European and American markets

1. To meet the standards of a powerful country in the back cover corrugated box industry with the progress of science and technology and compete for market share

in order to obtain a large enough sales share of the back cover corrugated box in the European market, a major company in a country completely adopted the technical standard of German corrugated box materials (din55468-1987). This standard uses two important data to regulate corrugated paper, that is, T represents the peak distance of the corrugated groove in the paper, and H represents the height of the corrugated groove in the paper. Taking two data as basic parameters, corrugated paper is divided into four types. On the surface, cartons (boxes) designed according to paper materials will differ in size due to different types. In fact, what is more important is the difference in strength of corrugated cartons (boxes). The process designer must clearly know that the transverse compressive strength of corrugated board is far less than its longitudinal compressive strength. In common box (box) type, the four side walls that play the role of compression are vertical corrugated grooves. The corrugated carton (box) with back cover is die-cut into blanks from a piece of cardboard, and then folded at right angles around the press marks to form. The four side walls of the carton (box) after forming are vertical corrugated grooves. Therefore, Carey Carter formula is used instead of APM formula for strength check calculation in design

the process designer should also know that the strength of the paper also depends on the strength of the base paper and the number of corrugated layers. The strength of base paper is set in other standards in Germany. The number of corrugated layers and the paper materials used for the back cover corrugated box (box) are mostly single slot type and double slot type. As the volume of paper with more than two corrugated layers increases significantly, universal back cover cartons (boxes) are rarely used

2. Based on domestic corrugated paper resources, standardize the process design of die-cutting blanks

the rapid development of China's corrugated paper industry has provided a rich supply of paper for the processing industry of cartons (boxes, the center continues to increase its efforts in the public service platform). Therefore, selecting materials according to market demand and designing die-cutting blanks according to specifications are the best way to improve the competitiveness of enterprises in the international market

when designing, the most important thing is to follow the following standard procedures, namely:

① determine the main load in the process of product circulation

② calculate the compressive strength of cartons that meet the environmental requirements

③ draw the die-cutting blank structure diagram of the corrugated carton (box) with the back cover

④ use the corresponding calculation formula to check the strength, mainly to calculate the strength coefficient s of the paperboard used

⑤ check the table to determine the initial clamping force of the base paper and the shape of the ridge

second, the three elements of the forming process design of the blank of the back cover corrugated box

industrialized machine bonding molding has a very high labor productivity. In order to make the high-speed operation smooth, it is required to establish which inner edge is the benchmark when designing the die-cutting blank, that is, the so-called gauge edge. Especially for cartons requiring high precision, tolerance calculation should be carried out according to requirements. Before the machine is successfully bonded into the stacking system (collector), it is counted by the folded indentation edge on the outside of the forming box. Its requirements are relatively applicable to the testing experiments of the abrasion resistance of the printing ink layer of printed matter, the abrasion resistance of the photosensitive layer of PS plate and the abrasion resistance of the surface coating of related products. In other words, we should pay attention to the gauge edge in the design without paying too much attention to others, so as to reduce the production cost as much as possible. For this reason, the carton forming process design should understand three elements:

first, the R2 indentation line of the corrugated carton blank at the back cover cannot be tilted to the left like a cardboard

this is because corrugated grooves are everywhere on the surface of corrugated paper. If R2 is inclined, there will be quality problems during high-speed pre folding and bonding of the machine - frequent deviation of the reference line, inaccurate folding of the back cover tongue P and the bonding tongue K, and the final forming 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, generally the maximum is 40 mm

third, because the cutting staggered line Z of the die-cutting indentation bevel tongue P is an indentation, which is staggered with the cutting (long) hole, that is, a certain section of Z1 is an indentation, and the same section of Z2 should be cut (long) hole, so after the bevel tongue P is folded, it must be pressed across the surface with a large extrusion force along the length direction of Z to enhance the sealing force at the bottom of the carton. In order to ensure the accuracy of this element and simplify the process, usually R1 and R3 indentation lines are not pre folded

III. grasp the influence of the blank design of the corrugated box at the back cover on the gluing accuracy

1 Grasp the forming law of bonding accuracy from the process characteristics of "skew to right"

when cutting the blank of the corrugated box at the back cover, it should be ensured 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 taking R5 as the benchmark, and the bottom line is offset to the right. Facts have proved that the rightward deviation is better than the left deviation. After many sampling tests, R1 ~ R4 lines coincide with the corrugated groove or deviate slightly to the right, which is opposite to the folding direction of the back cover tongue P, resulting in a "skew to the right" trend during the process molding. In this way, the box pasting accuracy can usually reach ± 1.5mm, and the finished product quality is high. Therefore, if we can fully grasp this process characteristic in the design and obey the unique law of corrugated paper back cover molding, we can ensure that the gluing box can meet the requirements of high precision

2. Grasp the design of the best ratio of the blank height and length of the back cover corrugated box

on the industrialized full-automatic box gluing machine, pre fold and glue the back cover corrugated box. In order to ensure the safety, reliability and smooth economic operation of the whole production process of the machine, there is always an optimal ratio between the height h of the carton die-cutting blank and the blank development length C (excluding the bonding tongue K) without other auxiliary tools or devices

this optimal ratio is related to the quality of base paper, the degree of industrialization, and even the environment of the workshop during operation. As designers, they should pay full attention to it. In particular, after considering many factors when using domestic paper materials, we have formed our own brand design specifications to show our strength. (end)

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