The reason for the edge burst of the outer packaging carton is the same as that of the color box, but the water content and the folding endurance of the paper type are too low. To find out the cause, we need to take targeted measures to improve it. The packaging manufacturer will explain several practical solutions. The following points:
I. How to ensure the moisture content of packaging carton board
- Ensure proper drying during painting. Generally speaking, the adoption of large diameter exhaust pipe and the installation of cooling equipment on the drying pipe can prevent the color cardboard from being too dry and fragile during curing.
- In general, the moisture content of the colored paperboard can reach more than 10%. However, when the weather is hot and dry, and the moisture content is very low, the glue moisture evaporates quickly, and the moisture content of the mounted cardboard is still very low. At this time, we might as well use the wet water roller of the machine to wet the water on the back of the cardboard, and use glue with low solid content to increase the amount of glue coating, so that the moisture content of the cardboard can be firmly fixed.
- If the water content of the mounted color paperboard is too low, the monochrome printing machine or flexographic printing machine can be used to reprint the water. After printing water, seal the cardboard tightly with plastic film, and die cut until the cardboard reaches water balance the next day. Pay attention to the carton fitting as soon as possible. If it needs to be placed for a period of time before fitting, it needs to be sealed with “stretch film” to avoid premature loss of water. In the past, coated white cards with different folding endurance were selected according to different paperboards and moisture content. For most single pit cardboard outer packing cartons, there are few broken lines because of the low tensile strength when shaking. However, for high-strength corrugated double corrugated cardboard, it is not allowed to use white cards that do not meet the weight of grams. Moreover, it is not allowed to cover the surface layer, so it is necessary to equip the whole wood pulp white card with better folding resistance.
II. Test method for folding resistance of white card coating:
- Use a paper cutter (pay attention to ensure that the straight grain direction of the paper is perpendicular to the long side) to cut five samples with a size of 25050 mm at 231 ℃, and store them in a 522% environment for 4 hours.
- Bend the sample inward so that the two short edges overlap, and pay attention to ensure that the middle part of the sample is arc-shaped.
- Place the bent sample under the 10KG pressure roller, press the overlapping end, and push the pressure roller to rotate towards the middle of the sample to fold the rolled sample in half.
- After repeated reciprocating rolling, open the sample and observe whether there are cracks on the surface coating of hand origami after rolling. Cracks, indicating that the white card coating has good folding resistance; If there are slight cracks, the white card coating is generally folding resistant; In the case of obvious collapse, the folding resistance of the white card coating is poor.
III Minor improvement plan
- The membrane cutting plate shall be reasonably designed. High quality indentation steel wire shall have appropriate hardness standard, strong reliability, round head, arc symmetrical figure, small thickness error and complete specifications. The basic principle for selecting the die cutting of the outer packaging carton is: the thickness of the indentation steel wire is not less than the thickness of the paper, the thickness of the film cutting blade minus the thickness of the film cutting material, and then minus the correction value of 0.05~0.10 mm. The basic principle for selecting the indentation line is that the pressure is not less than the thickness of the paper, and the total width is equal to 1.5 times of the thickness of the indentation steel wire.
For example:
The paper type with a thickness of 0.40 mm is film cut,
The curvature of the film cutter is 23.80 mm,
The thickness of indentation steel wire is selected as 0.71mm
Indentation steel wire stiffness=23.80-0.40-0.10 (0.05-0.10)=23.30 (mm)
Thickness of indentation line 0.40 (mm)
Width=0.401.5 0.71=1.31 (mm).
In essence, the opening connection point is to draw out some total width openings at a specific position on the film cutting edge, so that the cartons after film cutting can be closed, which is conducive to the discharge of waste. The connection point is usually opened in the hidden place that is not easy to see after the outer packaging carton is formed, and the glue line needs to be bypassed. If the connection point can be seen after forming, the lower the connection point is, the better. Otherwise, when the waste is discharged, the connection point is not easy to separate, the type is torn, and the surrounding ink layer bursts. Total width of the connection point=paper thickness 0.20 mm
- When the space between the indented steel wires is too small, sponge tape shall be pasted to stretch, tighten the paper and relieve the pressure difference. In addition, when correcting the plate, the groove shape can be pulled out at the line pressing position, so that when the color box is folded and formed, a greater radian can play a role in mitigating the wire burst.
- If the user has no special requirements and there is no white cardboard with stronger folding resistance, the manufacturer can adopt reasonable process to improve it.
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