How to solve the problem of burst corners and bursts during color box processing
Release time:2021-07-09

In the dry season, due to moisture, the color box has burst corners and bursts in the process of die-cutting, bonding and packaging, which often plagues many packaging and printing companies. Next, let's take a look at how experienced technicians deal with this type of problem.

One. cause

1. Improper pressure causes a burst

1.1 There is foreign matter in the bottom plate indentation groove, which causes the pressure to increase sharply during die cutting. This is a common cause of bursting in production, and it is also a destructive cause. It will break the dark thread as a whole, leading to product scrap.

1.2 Run the version, that is, the die-cut version or the base plate is moved so that the steel wire falls on the outside of the indentation groove. The bursting caused by this reason is mainly concentrated on the dark line in the same direction, because the cutter or creasing knife is not closely matched with the wooden template, and it is deviated under pressure.

1.3 The thickness of the steel wire and the width of the bottom groove of the indentation do not match the paper material. According to the requirements of the die-cutting process, different steel wires should be used for different papers, as well as different thickness of the base plate and different dark line groove widths. If they do not match, it is easy to cause the dark line to burst.

2. The burst caused by the production process of die-cutting plate

2.1 When making the die-cutting plate, the position of the steel wire is improperly handled or there are burrs when the steel wire is cut off. In the die-cutting, if the product has surface treatment, such as laminating. In the mold

The burrs left on the steel wire during cutting will damage the tensile strength of the surface film. When the product is formed, the film cannot be stressed and will burst.

2.2 The steel wire at the hidden wire has a knife edge and an interface. Because the interface is not smooth, tearing will occur during die cutting.

2.3 When the sponge pad of the crimping knife is in an improper position, crimping will occur. Deformation and damage of the crimping knife will also cause the crimping to burst. In the dry season, due to moisture, the color box has burst corners and bursts in the process of die-cutting, bonding and packaging, which often plagues many packaging and printing companies. Next, let's take a look at how experienced technicians deal with this type of problem.

2.4 Whether the matching of the knife and thread on the die is reasonable. In particular, the paper thickness was not considered in the design, the knife and the thread could not effectively avoid the overlap, and interference occurred during the molding, which caused the excessive concentration of the force at the place, resulting in bursting.

3. Material quality issues

3.1 The water content of the paper is too low and the paper becomes brittle. This phenomenon occurs more often in winter. Due to the dry and cold winter weather and the low relative humidity in the air, it will directly affect the moisture content of the cardboard, causing the cardboard to break after pressing. Generally, the moisture content of the base paper is controlled at the upper limit (8%). -14%);

3.2 Paper-coated material The biaxially oriented polypropylene film has tiny gaps, which reduces the tensile strength. Laminating is a relatively common paper surface treatment method. Its main material is BOPP film. If the BOPP film is damaged before die cutting, the BOPP film cannot be stressed and burst when it is bent after die cutting. The bursting of the film only occurs in the film layer. With the addition of the stress points, it will extend along the bursting direction. The bottom paper does not burst, which means that it has nothing to do with the paper. If the film is not broken, the paper has nothing to do with the film. problem.

3.3 The paper is in the wrong direction. During die-cutting, if the indentation steel wire is perpendicular to the paper fiber direction, and the paper fiber is destroyed radially, the dark line is easy to bend, is well formed, and has a small angle; If it is damaged, the dark line is not easy to bend, and it is formed into a rounded corner with a large angle. It has a large support force for the outer layer of the paper and is easy to break. The directionality of the paper has little effect on the die-cutting of sheet-fed paper products. It is just not easy to form, but it is not easy to burst, but it has a greater impact on card-mounted card products. If it is not handled well, it will not only fail Well, it is easy to burst lines, mainly because the dark lines with parallel paper patterns burst in different positions, while the lines do not burst in the other direction.

3.4 The corrugated configuration is too high. The bursting strength and transverse ring compressive strength of the base paper are one of the influencing factors. If the folding resistance of the inner paper is too low, it will easily lead to bursting.

3.5 The mold has been used for too long. In die-cutting, the die-cutting plate will loosen after long time use, which will cause the die-cutting tool to bounce up during the die-cutting process, causing the cardboard crimping to burst. Due to the long-term use of the rubber pad, the uneven height of the rubber pad causes the pressure line to burst.

two. Process improvement

(1) There is a burst caused by foreign matter in the indentation groove. During the production, the sampling inspection shall be strengthened, and the sampling shall be controlled at a time of 200 sheets. This problem is relatively intuitive and easy to judge. It is necessary to clean up foreign objects in time and keep the base plate clean.

(2) If it is found that the version is running, the version should be re-uploaded immediately, and the die-cut version and the master plate should be locked.

(3) There is a commonly used calculation method for the burst caused by the mismatch between the thickness of the steel wire, the thickness of the bottom groove of the indentation and the material:

    Die-cut cardboard

    Suppose A: thickness of bottom paper, B: width of dark line groove, C: thickness of jammed paper, D: thickness of steel wire, then: D≥C; A≤C; B=(C×1.5)+D

    Die cut corrugated cardboard

    Suppose A: the thickness of the bottom paper, B: the width of the hidden line groove, C: the thickness of the corrugated board (card mounted tile), D: the thickness of the steel wire, E: the thickness of the corrugated board after flattening, then it should be: D≥E; A≤E ; B=(E×2)+D

(4) If the steel wire on the die-cutting plate has burrs or cutting edges, eliminate the burrs or cutting edges of the indentation knife. Use a grinding wheel or a file to round it or replace a thick knife. If two thin knives are used together, the effect will be better.

(5) When making the die-cutting plate, the dark line should be made into an arc corner or a steel knife to form it at a time.

(6) When the pressure line burst phenomenon occurs due to the improper position of the sponge rubber strip, you can use a sponge pad to stick it next to the mold line crimping knife to help destroy the corrugation at the cardboard pressure line to solve the burst phenomenon. The sponge pad should not be too soft, and a harder protective strip should be used.

(7) For the moisture content of the paper, die cutting should be produced in time after the cardboard comes out. It is not easy to store for too long to reduce the influence of relative humidity on the moisture content of the cardboard. For cardboard with low moisture content, water can be applied to the cardboard to reduce the phenomenon of bursting. .

(8) For bursting caused by inaccurate registration, perform a forming action and pre-fold 180° test after registration, and visually check whether the indentation line is offset.

(9) The mold should be checked frequently, and if the knife is found to be loose, it should be repaired or remade in time.

(10) The improvement plan for the bursting caused by the paper thread direction problem is:

    a. The silk direction of the color box without paper mounting should be perpendicular to the main line of molding to facilitate molding.

    b. The tile direction of the two-layered color box should be perpendicular to the paper direction, so that the color box has stiffness when it is formed.

    c. Three-layer mounting (tile board type) can adjust the wire direction appropriately according to the configuration of the tile board.

(11) Improvement plan for bursting caused by paper toughness and folding endurance (configuration):

    a. The toughness and folding resistance of paper mainly depend on the content of wood pulp during papermaking. The higher the wood pulp, the more long fibers that make up the paper, the better the toughness and folding resistance, and vice versa.

    b. The higher the burst resistance and box pressure requirements, the higher the corrugated configuration will be, and the higher the requirements for the tissue paper will be. At this time, the toughness and folding resistance of the face sheet will be required; the worse the corrugated configuration will correspond to the face sheet reduce;

    c. The company also needs to purchase a testing device to test the raw paper when it is fed, not just to decompose the grammage and whiteness.

(12) Improvement plan for film quality causing burst:

    a. Replace the raw material of the film;

    b. Change the feeding direction of the upper film;

    c. Modify the die-cutting knife version, extend the knife at the joint and U-shaped corner, and lift the pressure line at the plane hole by 0.5mm-0.7mm to slow down the cushioning force during folding;

(13) The improvement plan for the thickness of the material and the size of the ruler.

    a. For different materials, the R angle of the die must be greater than the thickness of the material when designing the die;

    b. The matching position of the knife, the line and the plane hole should not conflict or interfere during the molding, and should be avoided reasonably, especially when the main line and the tile direction of the mounted corrugated product are very easy to burst when the main line and the tile direction are the same during the molding.

    c. We have to work towards a low-weight and high-configuration, and we cannot blindly pursue a high-configuration.

three. Environmental factors and standards

(1) The temperature in the workshop is kept balanced

(2) Control of water content when mounting paper (18±3)

(3) Products with suitable moisture content during die-cutting (18±3)

(4) Pressure adjustment of the die-cutting machine (70% of the bottom paper is broken and the rest needs to be compensated for the bottom paper)

(5) The width and thickness of the die-cut scoring line (the thickness of the paper flat × 1.5 = the width of the scoring line)

(6) Inspection of die cutting die (visual inspection, steel ruler, vernier caliper)

(7) Techniques during molding

    a. The main line that needs to be glued should be folded 180 degrees.

    b. The fold of the top and bottom flap must be greater than 135 degrees.

    c. The secondary line should be folded more than 135 degrees.

    d. The corrugated board should be folded 90 degrees.

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