How to solve the problem of -explosive line- and -dark line -encountered in paper box die-cutting?

How to solve the problem of "explosive line" and "dark line" encountered in paper box die-cutting?

2020-10-13

Die-cutting is a key step in the processing of color boxes, and how to ensure the quality of die-cutting is an issue of great concern to printing houses. At present, the main problems faced by color box printing factories are long time for plate change, poor printing-to-cut accuracy, poor die-cutting quality, too much paper wool, too many connection points, irregular trace lines, slow production speed, and scrap rate. higher.

0 1

Die cutting accuracy is not high

The cause of the problem: The reason for the low die-cutting accuracy is the problem of the die-cut version and the problem of the printed matter.

• The hand-made die-cutting plate has a large error;

• Die-cutting indentation and the operating environment of the printing process are different will cause paper deformation, resulting in inaccurate position of the die-cutting indentation, especially after glazing and laminating, the deformation of the paper is more serious, affecting the accuracy of die-cutting.

Solution: Choose advanced die-cutting plate making technology to improve the precision of die-cutting plate.

Try to ensure that the die-cutting and indentation and the printing process are carried out in the same operating environment, or ensure the identity of the operating environment (ie the same temperature, relative humidity, etc.);

The glazing and laminating paper should be die-cut pretreatment to minimize the influence of paper deformation on die-cutting accuracy.

02

Die cutting indentation produces "burst lines" and "dark lines"

Cause of the problem: "Broken line" means that the pressure of the die-cutting indentation is too large, which exceeds the bearing limit of the paper fiber, and the paper fiber is broken or partially broken;

"Dark lines" refer to undesirable creasing lines, which are generally due to inappropriate selection of die-cutting plate and creasing steel wire, improper die-cutting pressure adjustment, poor paper quality, inconsistent paper fiber direction and die-cutting plate row knife direction, It is caused by the low water content of the paper, which leads to the decrease of flexibility.

Solution:

• Choose the right die-cutting version;

• Properly adjust die cutting pressure;

• Place the printed matter to be die-cut in the workshop for a period of time before die-cutting;

• Increase the relative humidity of the workshop environment.

• Minimize the tension on the paper.

In addition, there is a special situation, that is, when die-cutting hard pack cigarette packets, because the distance between the indentation lines in many positions is very close, if the height of the indentation steel wire is configured according to the normal situation, the paper Excessive pulling force will also cause "burst line".

Therefore, we should try to minimize the tension on the paper. There are two methods: one is to reduce the height of the indentation steel wire; the other is to reduce the thickness of the indentation bottom die strip, but the two cannot be used at the same time, otherwise it will not work. To a very good indentation effect.

A better method is to reduce the height of the indentation steel wire. The lowered height is usually 0.1～0.2mm, which should be determined according to the basis weight of the paper. The height of the indentation steel wire that needs to be reduced for paper with a basis weight of 350g/m2 or more is 0.2mm , The paper whose basis weight is below 350g/m2 should be reduced by 0.1mm.

0 3 The indentation line is out of position and not full

The cause of the problem: the indentation steel wire twists under the action of the die cutting pressure, which will cause the indentation line to run out of position; insufficient die cutting pressure will cause the indentation line to be insufficient.

Solution: The problem can be improved by replacing the die-cutting plate and increasing the die-cutting pressure.

04

Die cutting fuzzing, dusting

The cause of the problem: during die-cutting, the edges of the die-cut products are often not smooth and fluffy, especially at some of the edges closer to the indentation line.

This is because the rubber strips and indented steel wires on the die-cutting plate exert a tensile force on the paper when the die-cutting and pressing are performed, and the paper is broken by the generated tensile force when it is not completely cut through, and burrs appear.

Solution: First, choose different types of die cutters according to the paper. Die-cutting knives include straight-grain knives and horizontal-grain knives. The blades of the two kinds of patterns have different heights. The patterns and heights formed by the blades are different, which directly affect the quality of die-cutting and the service life of die-cutting knives.

In terms of avoiding die-cutting and fluffing, straight-grain knives are better than cross-grain knives; in terms of service life, short blades are better than high blades.

When die-cutting film-coated cardboard, a straight-grained high-edge knife should be used, and the edge of the knife should be polished. It is best not to use a one-time embossing process, otherwise too much pressure will have a great impact on die cutting;

When processing ordinary cardboard, a short blade should be used, and the texture of the blade should be determined according to the quality of the paper fiber.

Straight-grain knives should be used for paper with poor fiber or thicker fibers, and horizontal-grain knives can be used for paper with better fiber quality to increase the service life of die cutters.

Secondly, it is also possible to stick a 60° arched tape near the die cutter near the indentation steel wire to reduce the tensile force generated by the indentation steel wire on the paper during die cutting and pressing.

For example, when die cutting paper with a basis weight of 300g/m2, an indentation steel wire with a height of 0.4mm×1.3mm and 23.4mm is usually used. In case of this failure, a sharp-point indentation with a height of 0.4mm×1.2mm and 23.3mm can be used instead. In this way, the steel wire reduces the tension on the paper during die-cutting and pressing, and the problem of die-cutting fluffing can be basically solved.

0 5

Die-cut "pasted version"

Cause of the problem: Die-cutting "glued plate" means that the paper sticks to the die-cutting plate. There are several reasons for this failure:

• The density or hardness of the sponge rubber strip pasted around the die cutter is too small, and the resilience is insufficient;

• The cutting edge of the die cutting knife is not sharp, and the paper is too thick, which may cause the knife to clamp or stick when die cutting.

Solution: According to the distribution of die cutters, choose sponge strips of different hardness or replace die cutters.

0 6

Die-cutting "Loose Edition"

The cause of the problem: Die-cutting "loose plates" is mainly related to the die-cutting plate-making process and sponge rubber strips. If the shape of the job is complicated or there are a lot of jobs in arrangement, and the connection points on the die-cutting plate are small and few, it is easy to cause the die-cutting to loose the plate.

Solution: Properly increase the number of connecting points on the die-cutting plate, and try to keep the length direction of the printed matter consistent with the paper feeding direction when making the die-cutting plate.

0 7

Too many connections

The end users of the color box always require smaller and fewer connection points, and the manufacturer always makes the machine run faster, which increases the difficulty of the operator. In order to reduce the difficulty, the connection point should be at the stress point and be polished with a wire grinder. Use hard rubber or cork on the edge of the knife to prevent the connection point from breaking, so that the connection point can be smaller and less.

0 8

Irregular trace lines

Considering the needs of folding and pasting boxes, color boxes must have good indentation lines. More importantly, when these boxes are running on the automatic packaging machine, the opening force must be stable and consistent. In this way, choosing the right type of trace line is the basic element when die cutting. According to the thickness of the paper, choose the height and width of the mark line, and glue the appropriate mark line on the die-cut bottom plate. The indentation can achieve higher quality and make the box easy to fold.

0 9

Long version change time

The preparation work before changing the version should be done well. Using the center line of the equipment as a reference, you can easily and accurately set die-cutting tools, including full-size die-cutting plates, pre-installed bottom templates, and so on. At the same time, the tools are pre-installed outside the machine and the fine-tuning on the machine further reduces the adjustment time for repeated products. Under a good management system, the time for repeating product version changes, including automatic scrapping, can be completed within 30 minutes.

10

Slow production

The die-cutting speed of many color box printing plants is relatively low, such as 2000-3000 sheets/hour, while the die-cutting speed of some printing plants can be as high as 7000-7500 sheets/hour.

Using modern automatic die-cutting machines, operators can easily reach the highest production speed. The production speed is optimized by using the tools recommended by the equipment manufacturer. In addition, it can also achieve high quality products.

11

High scrap rate

The scrap rate of most printing plants is usually high. There will be some waste at the beginning of the die-cutting adjustment, which can be reduced by using the right tools and the right steps. The waste during operation is caused by shutdown and paper jam. Correct adjustment and accurate tool preparation can reduce the waste rate. In addition, manual waste removal will increase the scrap rate and reduce the profit margin.

With the gradual upgrading of the consumer market, consumers have higher and higher requirements for the appearance of product packaging. Therefore, it is very important for printers to do color box printing. As a key step of color box printing, the die-cutting process is only detailed Only by understanding the easy problems and solving them can we better complete the color box printing.