In the dry season of the weather, due to moisture, the explosion angle and popping problems of color boxes in die cutting, bonding and packaging often plague many packaging and printing companies. Let's take a look at how the senior technicians deal with this type of problem.
one. cause
1 Burst caused by improper pressure
1.1 There is foreign matter in the creasing groove of the bottom plate, which leads to a sharp increase in pressure during die cutting. This is a common cause of bursting in production and is also a destructive cause. It will cause the entire dark line to break and cause the product to be scrapped.
1.2 Running version, ie die-cut version or bottom plate, makes the steel wire fall outside the creasing groove. The burst caused by this reason is mainly concentrated on the dark line in the same direction, because the cutter or the indentation knife does not fit tightly with the wooden formwork and is deflected under the pressure condition.
1.3 The thickness of the steel wire and the width of the indentation bottom groove do not match the material of the paper. According to the requirements of the die-cutting process, different steel wires and different thicknesses of the bottom plate and different dark groove widths should be selected for different papers. If they are not matched, it is easy to cause the dark lines to burst.
2 die cut production process caused burst
2.1 When making a die-cut version, the position of the steel wire is improperly handled or burrs are left when the steel wire is cut off. In the die-cutting process, if the product is surface-treated, it is covered, for example. The burrs left on the steel wire during die-cutting will damage the tensile strength of the surface film. When the product is molded, the film cannot be subjected to stress and bursts will occur.
2.2 The knife steel wire at the dark line has a knife edge and an interface. Because the interface is not smooth, tearing occurs during die cutting.
2.3 When the position of the sponge pad of the knife is not proper, there will be a phenomenon of pressure line burst. The deformation and damage of the knife will also cause the pressure line to burst.
2.4 Whether the knife and the line on the die are reasonable. In particular, the thickness of the paper is not taken into consideration during design, and the knife and the wire cannot effectively avoid the overlap. When the molding occurs, the interference occurs, which causes the stress to be excessively concentrated and burst.
3 Material quality problems
3.1 The moisture content of the paper is too low and the paper becomes brittle. This phenomenon occurs more often in winter. Due to the cold and dry weather in winter, the relative humidity in the air is relatively low, which directly affects the moisture content of the paperboard, resulting in cracking of the paperboard after pressing. Generally, the moisture content of the base paper is controlled at the upper limit (8%). -14%);
3.2 Paper coating material Biaxially oriented polypropylene film is slightly chipped, resulting in reduced tensile strength. Lamination is a common paper surface treatment method. The main material is BOPP film. If the BOPP film is damaged before die-cutting, BOPP film can not be forced to burst due to damage after die-cut. The burst of the film occurs only in the film layer. As the stress point increases, it will extend along the burst direction, and the underlying paper will not burst. This indicates that the film has nothing to do with it. If the film is not broken, the film has no relation with the film. problem.
3.3 The paper is not correct. During die-cutting, if the indentation steel wire is perpendicular to the paper fiber direction, and the fiber of the paper is broken radially, the dark line is easy to bend, the molding is good, and the angle is small; if the indentation steel wire is parallel to the paper fiber direction, the paper is not in the transverse direction. Damaged, the dark line is not easy to bend, forming a rounded corner, a large angle, for the paper outer force, easy to break. This directionality of paper has little effect on the die-cut of sheetfed products, but it is not well formed, but it is not easy to burst the wire. However, it has a greater impact on the products of the card. If the handling is not good, not only the molding is not Well, it is also easy to burst the line, mainly the dark lines of parallel paper lines burst at different positions, and the other direction does not burst.
3.4 Corrugated configuration is too high. The bursting strength and lateral crushing strength of the base paper are one of the influencing factors. If the folding paper is too low, it can easily cause a burst.
3.5 The mold is used for too long. In the die-cutting, after the die-cut version is used for a long time, the crimping knife will be loosened, resulting in that the crimping knife pops up during the die-cutting process, causing the paperboard-pressing line to burst. Due to the prolonged use of the pad, the rubber pad bursts due to the unevenness of the pad.
two. Process improvement
(1) There is a burst of foreign matter in the crease groove. Strengthen the sampling force during the production and control the sampling at 200 times. This question is more intuitive and easy to judge. It is necessary to clean the foreign matter in time and keep the bottom plate clean.
(2) Found that running version of this situation should immediately re-print, and lock the die-cut version and the bottom plate.
(3) There is a common calculation method for the burst caused by the thickness of the steel wire, the thickness of the indentation bottom tank and the material mismatch:
Die-cut cardboard
Let A: bottom paper thickness, B: dark groove width, C: cardboard thickness, D: steel wire thickness, there should be: D ≥ C; A ≤ C; B = (C × 1.5) + D
Die-cut corrugated cardboard
Let A: bottom paper thickness, B: dark groove width, C: thickness of corrugated board (card watts), D: thickness of steel wire, E: thickness of corrugated board after flattening, there 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, the burr can be eliminated or the edge can be rounded or replaced by a grinding wheel or a guillotine blade. The use of two thin-type knives combined with a better effect can be used.
(5) In the production of die-cut version, the dark line should be rounded or a steel knife should be formed once.
(6) When the phenomenon of pressure line burst occurs due to the improper position of sponge rubber strips, it can be affixed next to the crimping knife of the mold with a sponge pad to help destroy the corrugation at the cardboard pressure line so as to solve the burst phenomenon. The sponge pad should not be too soft and should use its own harder bead.
(7) For paper moisture content, cardboard should be produced immediately after die-cutting, not easy to store for too long, reduce the impact of relative humidity on the moisture content of the paperboard, for low water content paperboard, you can smear water on the cardboard to reduce the burst phenomenon .
(8) Burst caused by overprinting is not allowed. After molding, the molding operation is performed and the 180-degree test is pre-folded. Visually inspect the indentation line for deviation.
(9) The mold should be inspected frequently and it is found that the knife must be repaired or re-created in time.
(10) The burst improvement solution due to the problem of paper webs is:
a. The color of the cassettes, which does not pick up the paper, is perpendicular to the forming main line, which facilitates molding.
b. The color of the two-story color box should be perpendicular to the paper direction, so that the color box can have stiffness.
c. The three layers (tiles) can be adjusted according to the configuration of the tile.
(11) Crack improvement solutions due to the toughness and folding resistance (disposition) of the paper:
a. The toughness and folding resistance of paper are mainly determined by the wood pulp content in papermaking. The higher the wood pulp is, the higher the long fibers of the paper are. The toughness and folding resistance are better, and vice versa.
b. Breaking resistance and box pressure requirements The higher the corrugation configuration, the higher the requirement for facing paper. At this time, toughness and folding-resistant face sheets will be required; the worse the corrugation configuration, the more opposite the requirements of the opposing sheet. reduce;
c. The company also needs to purchase a testing device to test the raw material when feeding the material. It should not only degrade the grammage and whiteness.
(12) The improvement of the burst caused by the quality of the film:
a. Replace the raw materials of the film;
b. Change the direction of film feeding;
c. Modify the die cutter plate, extend it at the knife-knife and U-shaped corners, raise the pressure line at the plane hole by 0.5mm-0.7mm, and slow down the buffering force when folding;
(13) The thickness and size of the material are improved.
a. For different materials, the R angle must be greater than the thickness of the material when designing the die.
b. The position of the knife and the wire and the plane hole must not be interfered or interfered during molding, and reasonable avoidance is required. In particular, when the main wire and the shim are molded in the same direction, the corrugated corrugated product can easily burst.
c. We must work toward a low-weight, high-profile configuration. We cannot pursue high-profile configuration.
three. Environmental factors and standards
(1) The temperature in the workshop is balanced
(2) Control of water content when picking paper (18±3)
(3) Appropriate moisture content when die-cutting product (18±3)
(4)Pressure adjustment of the die cutting machine (70% of the bottom paper punches the rest of the paper to make up)
(5) Width and thickness of die-cut lines (thickness of paper squashed × 1.5 = width of reticle)
(6) Inspection of die cutter (visual, steel ruler, slide caliper)
(7) Molding techniques
a. The main thread that needs to be glued is to be folded 180 degrees.
b. The upper and lower flaps must be folded more than 135 degrees.
c. Sub-line should be folded more than 135 degrees.
d. Corrugated board is to be folded 90 degrees.
