Every Die-hard Die-cutting--Analysis of Die-cutting Problems (4)

4 Burst (dark line)

Burst refers to the fact that when the product is die-cut or when the finished product is folded, the paperboard is subjected to excessive die-cutting pressure, which exceeds the tolerance of the cardboard fiber, and breaks or partially breaks the paperboard fibers at the indentation. "Dark line" refers to an indentation line that should not be present. This is a problem that often occurs in die cutting, especially when the weather is dry. Specific analysis should be based on specific circumstances.

â–  Die cutting pressure is too large. Adjust the pressure of the die-cutting machine properly so that the waste edge is just separated. When the cardboard thickness is too large, the choice of the height of the die-cutting steel wire should be reasonable, and the padding under the steel plate should be appropriately increased or decreased in order to obtain the best pressure. During folding and forming, if the paperboard cracks are cracked on the outside, the reason is that the indentation is too deep or the width of the indentation is not enough: if the inside of the paperboard is cracked, the indentation force of the molding is too large and the folding is too deep. The thickness of the steel wire can be reduced appropriately; the width of the indentation line can be widened according to the thickness of the paperboard; the pressure of the die-cutting machine can be appropriately reduced; or a steel wire with a slightly lower height can be used;

â–  The moisture content of the paperboard is low, resulting in a drop in flexibility and brittleness of the paper causing the popping. Especially after high-temperature polishing, it is more likely to die when die-cutting. The humidity in the workshop environment should be increased or the board should be placed in the workshop to adjust the humidity before the die cutting. The water can also be used to feed the back of the paper, increase the water content, make it flexible, and then put on the die-cutting machine. The fiber direction of the paper should be consistent with that of the die-cutting plate knife;

■ The printed surface has a large area of ​​deep-colored solids, which can be explosively colored and burst after die-cutting. No ink additive is added or reduced in dark ink during printing to enhance the adhesion of the ink on the paper, which can reduce the explosion color and popping phenomenon. The accumulation of paper powder that has fallen off the kerf can also affect the production. Operators should promptly remove clean paper, foreign objects, etc.;

â–  In the die-cutting of the cigarette case, because the distance between the indentation lines in many places is very close, if the height of the indentation steel line is configured according to the normal conditions, the pulling force on the paper during molding may be too large, which may also cause explosion. line. Therefore, efforts should be made to minimize the tension on the paper. One is to reduce the height of the indentation steel wire. The second is to reduce the thickness of the indentation bottom mold strip. Both of them cannot be used at the same time, otherwise no good indentation effect is achieved. A better method is to reduce the height of the indented steel wire, and the reduced height is usually 0.1 mm to 0.2 mm. According to the thickness of the paper to determine how much lower.

5 Indentation line is irregular

The main performance of the indentation line running analysis is as follows:

â–  The indentation groove on the wire liner is too wide and the position of the paperboard is indefinite. It is required to keep the width of the indentation groove when making the stencil;

â–  Insufficient thickness of steel lined pad, irregular groove angle, extra rounded corners. The elimination method is to replace the steel wire pad in time, increase the thickness of the steel pad, and trim the groove angle;

â–  row knife, solid knife tightness is not suitable. Steel is too tight, the bottom can not achieve the ideal contact with the plane of the pressure plate, indentation prone to twisting; Copper is too loose, easy to move around indentation. When the plate cutter is required to make plates, its tightness should be suitable and no shaking phenomenon can occur. Change the template if necessary;

â–  Insufficient die-cutting pressure can cause indentation. In the case of ensuring normal operation, increase die-cutting pressure appropriately to improve this problem.

Application rules

Die cutters, indentation lines, elastic tapes, and pressures are several major influencing factors in the cutting process. After analyzing the above failures, we can see that the problems that arise in production are mainly related to these factors, and we now choose to apply them. The rules are summarized as follows:

1 Die cutter

Die cutter has single-sided, double-sided points, edge teeth, linear points, its thickness is also divided by 0.5mm to 1.5mm specifications. Choosing the right model and specification of die cutter is the key to ensure die-cutting quality. Good quality die cutter steel quality, exquisite decarbonization, good heat treatment, high precision. The choice of die cutter depends on product specifications and materials, customer requirements, and the complexity of the box. Circular die cutting commonly used toothed knife, the thicker the cut cardboard, the number of teeth per unit length of the die cutter should be less, and vice versa, in order to achieve the best pressure.

2 indentation line

As with the choice of die cutter, the choice of indentation line is also very critical, product indentation is not obvious or fracturing, is often caused by improper selection of indentation line. High-quality indentation steel wire should be moderate in hardness, strong in stability, smooth in thread head, symmetrical in arc axis, low in height and thickness deviation, and complete in specifications. The indentation line height has a variety of specifications and should be selected according to the thickness of the indentation board. (Note that for corrugated board, the corrugation should be flattened to measure thickness).

Generally should follow the formula: indentation line height two die cutter

Height - the thickness of the cut cardboard - the thickness of the pad

Suppliers are all provided with reference marks on the indentation line; for reference, but in practical applications, they should be flexibly selected according to their own situation.

3 Strips

During the die-cutting process, the strip directly affects the speed and quality of die-cutting. If it is used improperly, it will result in more paper, trimming, and unsmoothing of the product. The rational choice and use method is:

Hardness selection: Generally, the hardness of the strip used on both sides of the knife line is 35HS--40HS (Shore hardness); in the narrow place, the strip with higher hardness is used, and the general hardness is 60HS.

Height selection: Normally the strip should be 2mm higher than the blade peak, and the harder strip placed in the narrow place should be 0.5mm higher than the blade.

When placing the tape, it should be continuously affixed to both sides of the embedded knife line, generally 1mm from the knife line is appropriate.

4 Adjustment of layout pressure

The proper pressure makes the finished product cut a thousand edges; the tussle is not hairy, easy to remove the waste edge, and the die cutter is not easy to wear. When working, the pressure of the machine should be roughly adjusted. It should be small and not large, and gradually pressurize. Then under the steel plate under the pad, after the pressure test to observe whether the edge of the trimming edge is easy to separate, in the absence of separation at the local pad, so that the layout of the die cutter pressure uniformity, balance and then gradually increase the pressure of the machine. The pressure of the indentation line depends on factors such as the thickness and height of the indentation line. The ideal pressure needs to be pressed out for inspection.

The above are some of the common problems in production. Of course, many other problems will arise in actual production. The operator can analyze the specific situation to find out the possible causes and take corresponding measures to solve it. As long as you are familiar with the basic principles of die-cutting process, you will continue to summarize and master various techniques in actual production and operation. You will be familiar with the performance of production equipment and strictly enforce the requirements of the production process. This will eliminate the occurrence of production in a timely and correct manner. Various problems create favorable conditions for the smooth production of high-quality die-cut indented products.

Author: Li Feijiang Southern University

Source of information "Corrugated carton" 2005, 9