In the dry weather season, because of the moisture, the burst angle and bursting of Kunshan color box during die cutting, bonding and packing often trouble many packaging and printing companies. Below, let's take a look at how technicians deal with this type of problem.

Kunshan Color Box

    One. Cause of attack

    1. Improper pressure causes burst

    1.1 There is a foreign body in the indentation groove of the bottom plate, which causes the pressure to increase sharply during die cutting. This is a common cause of bursting in production and is also a cause of damage. It will cause the dark lines to crack as a whole, resulting in product scrap.

    1.2 The running version, that is, the die-cut version or the bottom plate is moved, so that the steel wire falls outside the indentation groove. The bursts caused by this cause are mainly concentrated on the dark lines in the same direction, because the cutting knife or the indentation knife does not cooperate closely with the wooden formwork, and the deflection occurs under pressure.

    1.3 The selection of steel wire thickness and indentation bottom groove width does not match the paper raw material. According to the requirements of the die-cutting process, different steel wires should be selected for different papers, as well as base plates of different thicknesses and different dark line groove widths. If they do not match, it will easily cause the dark line to burst.

    2.Burst caused by die cutting plate manufacturing process

    2.1 Improper handling of steel wire orientation when manufacturing die-cut plates or burrs left when steel wire is cut. If the product has been treated during die cutting, such as lamination. Burrs left on the steel wire during die cutting will damage the pull-up strength of the external film. When the product cannot be stressed when the product is formed, it will burst.

    2.2 Steel knife at the dark line The steel wire has a knife edge and an interface. Because the interface is not smooth, it will appear tearing during die cutting.

    2.3 When the orientation of the sponge pad of the crimping knife is not appropriate, the crimping burst will appear. The deformation and damage of the crimping knife will also cause the crimping burst.

    2.4 Whether the knife and line configuration on the die is reasonable. Especially the thickness of the paper was not taken into account in the design. The knife and the thread could not be effectively avoided in the overlap. During the molding, dry contact occurred, which caused excessive stress to gather there and burst.

    3. Material quality issues

    3.1 The water content of the paper is too low, and the paper becomes brittle. This phenomenon is mostly seen in winter, because the weather is dry and cold in winter, and the relative humidity in the air is low, which directly affects the moisture content of the cardboard. After forming the creasing, the cardboard has a cracking phenomenon. Generally, the moisture content of the base paper is controlled at the upper limit (8%). -14%);

    3.2 The biaxially oriented polypropylene film of the paper has fine notches, and the tensile strength decreases. Lamination 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 when it is bent after die cutting and it can burst. The bursting of the film only occurs in the film layer, and it will extend along the bursting direction with the increase of the stress points. The bottom paper does not burst, which indicates that it has nothing to do with the paper. If the film is not broken, the paper has nothing to do with the film, and the paper has problem.

    3.3 Paper orientation is wrong. During die cutting, if the direction of the indentation steel wire and the paper fiber is straight, and the paper fiber is damaged in the radial direction, the dark line is simply bent, the shape is good, and the viewpoint is small. If it is damaged, the dark line is not easy to bend, is formed into rounded corners, has a large viewpoint, and has a large supporting force on the outer layer of the paper, which simply breaks. This orientation of the paper has little effect on the die-cutting of single-sheet products, but the molding is not good, but it is not easy to burst the line, but the card-mounted card products have a greater impact. If the processing is not good, not only the molding is not good Well, it is also simple to explode the line, mainly the dark line parallel to the paper pattern explodes the line in different directions, while the other direction does not explode the line.

    3.4 Corrugated equipment is too high. Burst resistance and transverse ring compressive strength of the base paper are one of the influencing factors. If the foldability of the lining paper is too low, it will simply cause a burst.

    3.5 Mould use time is too long. In die-cutting, after a long-term use of the die-cutting plate, the crimping knife will become loose, which will cause the crimping knife to pop up during the die-cutting process, forming a cardboard creasing line burst. Because of the long-term use of the rubber pad, the unevenness of the rubber pad forms a pressure line burst.

    two. Process improvement

    (1) There is a burst of foreign body in the indentation groove. The sampling strength should be strengthened at the time of production, and it should be controlled once in 200 sheets. This problem is relatively straightforward, and it is easy to judge. You must clean up foreign objects in time and keep the bottom plate clean.

    (2) If you find that the running version is in this situation, you should immediately start from the top, and lock the die-cut version and the bottom version.

    (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 raw material:

    Die-cut jam

    Let A: the thickness of the backing paper, B: the width of the dark line slot, C: the thickness of the cardboard, D: the thickness of the steel wire, then: D≥C; A≤C; B = (C × 1.5) + D

    Die-cut corrugated board

    Let A: the thickness of the backing paper, B: the width of the dark line groove, C: the thickness of the corrugated cardboard (card-mounted tile), D: the thickness of the steel wire, E: the thickness of the corrugated cardboard after flattening, then: D≥E; A≤E ; B = (E × 2) + D

    (4) If the steel wire on the die-cutting plate has burrs or cutting edges, the burrs or cutting edges of the indentation knife can be rounded with a grinding wheel or file or replaced with a thick knife. If two thin knives are used in combination, the effect is better.

    (5) When manufacturing the die-cut plate, the dark line should be made into an arc angle or a steel knife at one time.

    (6) When the pressure burst occurs due to the improper orientation of the sponge rubber strip, you can use a sponge pad to stick around the crimping knife of the mold to help damage the corrugation at the press line of the cardboard to achieve the treatment of the burst. The sponge pads should not be too soft, and should use their own hard guard strips.

    (7) Regarding the moisture content of the paper, the cardboard should be die-cut in time after it comes out, and it is not easy to store for too long, reducing the impact of relative humidity on the moisture content of the cardboard. For cardboard with low moisture content, you can modify the cardboard with water to reduce the burst phenomenon. .

    (8) For the burst formed by the registration process, do the forming action after the registration process and pre-fold the test at 180 degrees, and visually check whether the indentation line is offset.

    (9) The mold should be checked frequently and found that the knife has looseness, which should be repaired in time or manufactured from scratch.

    (10) The burst improvement plan due to paper filament orientation problems is:

    a. The color of the unboxed paper box should be straight with the main line of the molding to facilitate molding.

    b. The two-layer color box tile direction and paper direction should be straight, so that the shape of the color box has stiffness.

    c. Three layers (tiles) can be adjusted according to the equipment of the tile.

    (11) Burst improvement plan due to paper resistance and folding resistance (equipment):

    a. Paper resistance and folding resistance are mainly determined by the content of wood pulp during papermaking. The higher the pulp, the more long fibers that make up the paper, the better the resistance and folding resistance, otherwise the poor.

    b. The higher the resistance to breakage and box pressure, the higher the corrugated equipment will be, and the higher the requirement for the face paper. At this time, the resistance and folding resistance will be required; the worse the corrugated equipment is, the higher the requirements will be decline;

    c. The company also needs to set up a testing device to test the raw paper when it is fed. It can not only decompose the weight and whiteness.

    (12) Improving plan of burst caused by membrane quality:

    a. Replace the raw materials of the film;

    b. Change the paper feed direction;

    c. Correct the die-cutting knife version, extend it at the knife connection and U-shaped corner, and raise the pressure line at the plane hole by 0.5mm-0.7mm to slow down the buffering force when folding;

    (13) The plan to improve the thickness of the raw materials 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;

    b. The knife and thread and the adjustment position of the aircraft hole cannot be inconsistent or dry during molding. Reasonable avoidance is required, especially for the framed corrugated products. When the main line and the tile direction are in the same direction, bursting is easy to occur.

    c. We must work towards low weight and high equipment. We cannot blindly pursue high equipment.

    three. Environmental factors and standards

    (1) The temperature in the workshop is balanced

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

    (3) Suitable moisture content products for die cutting (18 ± 3)

    (4) Pressure adjustment of the die-cutting machine

    (5) Width and thickness of die-cut reticle (thickness of paper flattened × 1.5 = reticle width)

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

    (7) Techniques during molding

    a. The main line of the box needs to be folded 180 degrees.

    b. The fold of the upper and lower swing covers should be greater than 135 degrees.

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

    d. The corrugated board should be folded back 90 degrees.

 Kunshan Printing