When using labels, sticking labels is an important step. At the label sticking site of the printing machine, different problems will occur. Here are two common label sticking problems – label dropping.
A certain company in Xi'an, when applying labels, often encounters the problem of part of the labels sticking directly to the back of the bottom paper after the roll of labels is opened, causing the label sticking machine to not produce normally and causing a lot of waste.
After carefully inspecting this batch of finished labels, several wound labels were peeled off. The following problems were discovered: some labels randomly transfer to the back of the bottom paper, resulting in partial blanks on the wound labels. In addition, the labels stuck on the back of the bottom paper all have glue on one side and no glue on the other side. Among the labels that have not fallen off, some also have the problem of having glue on one side and normal on the other side.
In such cases, it generally has nothing to do with the printing and die-cutting of the labels, but with the splitting of the materials after die-cutting and the final inspection and rewinding process. After carefully inspecting the label slitting machine of the printing plant, and observing the slitting process of the labels being slit, the following problems were found:
① After die-cutting, the material does not fall off on the slitting machine before or after slitting, but after being rewound, a small amount of intermittent, irregular label sticking occurs. The label transfers from the bottom paper.
② The surface of the slitting blade has obvious adhesive. During slitting, the slitting blade axis is fixed, while the material sometimes has a deviation or a snake-like phenomenon in the slitting process. At this time, the adhesive on the side of the label will stick to the surface of the slitting blade. If these adhesives on the slitting blade are not cleaned up in time, they will stick to the bottom paper or the label surface, and the labels with adhesive on one side will stick to the back of the bottom paper after rewinding, which is the main reason for the label sticking to the bottom paper.
③ The label interval size is too small. If the material swings left and right, it will cause adhesive. It is a schematic diagram of the size of the label waste discharge and the position of the slitting blade. As can be seen, the waste discharge size in the middle of the two rows of labels is 3mm, and after separation, the size of each side is 1.5mm. The thickness of the slitting blade is 1mm, and the distance between the slitting blade and one side of the label is only 0.5mm.
In this case, if the material moves slightly to the left or right, it will cause the slitting blade to contact the side of the label, that is, the adhesive, and the adhesive on the side of the slitting blade will accumulate more and more. The same will be transferred to the side and surface of the label, so this side of the label is very easy to stick to the adhesive.
④ The slitting and rewinding after splitting is too tight, that is, the winding tension is too large, which will cause adhesive around the label and increase the risk of label sticking and dropping. The winding tension must be reduced.
The above are the reasons found on the spot in the printing plant. For this reason, we have formulated solutions and achieved the final solution effect.
① Increase the label waste discharge size from the previous 3mm to 4mm, which can reduce the risk of adhesive on the side of the label.
② After the semi-finished label is die-cut, it is first rewound on the rewinding machine to make its end face flat and have a certain tension, which can avoid deviation or snake-like feeding on the slitting machine. At the same time, a baffle device is installed on the material feeding position of the slitting machine to avoid the material swinging left and right, affecting the quality of slitting.
③ Install a degumming device on the small slitting machine. The installation of the degumming device has two main purposes: one is to lubricate the slitting blade, because the wool felt in the device can put silicone oil or other lubricating oil to reduce the wear of the slitting blade and keep it sharp. The second is to keep the adhesive on the surface of the slitting blade in the wool felt, avoiding the adhesion of the slitting blade, and keeping the blade sharp and clean. It should be noted that the degumming device should be maintained regularly, remove the adhesive, add lubricating oil, and also avoid the shedding of adhesive particles, causing other quality problems.
The printing plant agreed with the customer's opinions, and all the labels with problems were returned and destroyed. The labels were printed and processed again according to the new solution. After the new labels were used by the customer, the previous problems did not occur. The customer was very satisfied with the cooperation of the printing plant and expressed the desire to cooperate with printing more labels for a long time.
This case is the process of continuous learning from experience and lessons by the label printing plant, and it is something that every label printing plant must pay special attention to in order to avoid waste and loss.