What should I do if there is adhesive overflow in the die-cutting of self-adhesive labels?
May 21, 2023
In the daily production process of self-adhesive labels, the problem of overflow during die-cutting is very common, which seriously affects product quality and production efficiency, and troubles operators. In this article, Superreliable Technology Group analyzes the reasons for die cutting adhesive overflow from two perspectives and provides some solutions.
1. Overflow leaded by raw material
Adhesive materials are usually divided into two categories: paper and film, depending on the surface material. Among them, the adhesive material of the film surface material is relatively prone to adhesive overflow, because the film material completely does not absorb adhesive, and the surface tension of the adhesive surface is also relatively low, making it difficult to firmly bond with the adhesive layer; The self-adhesive material of paper surface materials may sometimes overflow, such as materials with excessively thick adhesive layers or strong adhesive fluidity.
So, how to determine if the overflow is caused by raw materials? Here is a relatively simple way to determine: peel off a die-cut label and look at the overflow situation of the label in front of the light. Generally speaking, the overflow caused by raw materials is generally caused by the overflow of glue at the edge of the label. If there is only one or partial overflow of glue on the label, most of it is not caused by the raw material.
There are two reasons for the overflow caused by raw materials: one is the strong fluidity of the glue, and the other is the thick coating of the glue. If it is a batch defect, simply replace the raw materials; If it is a function problem, such as frozen glue label and tire label, these materials themselves require very thick glue and strong liquidity, and glue overflow is almost inevitable during die cutting.
Once encountering this problem, on the one hand, freezing methods can be adopted to reduce the fluidity of the adhesive. That is, raw materials can be placed in a cold storage or freezer before production to reduce the fluidity of the adhesive. At the same time, ways can be found to minimize the time from material loading to die-cutting, so that the adhesive is not easy to overflow during die-cutting. On the other hand, while ensuring stable printing tension, the amount of material passing through the guide roller should be minimized as much as possible, because under the action of equipment tension, the contact between the material and the guide roller will compress the adhesive layer, causing the adhesive to overflow.
We recommend to use adhesive label material from Weifang Superreliable Technology to avoid above problems.
2. Overflow leaded by die cutting
A. overflow leaded by unsuitable die cutting knife
The blade for die-cutting film materials is different from the blade for die-cutting paper materials, mainly in terms of angle and hardness. The smaller the angle, the sharper the blade and the easier it is to cut through the material. Generally speaking, the blade angle used for die-cutting film materials is 30 ° to 42 °, and the blade angle used for die-cutting paper materials is 52 °. This is because film materials have much higher requirements for die-cutting than paper materials. Generally speaking, film materials require that all the surface materials be cut off during die-cutting, at least 4/5 of which needs to be cut off, while paper materials require that 2/3 of the surface materials be cut off during die-cutting.
For hardness, the blade hardness of die-cutting paper materials is generally required to be above 58 ° Rockwell, while the blade hardness of die-cutting film materials is higher than that of die-cutting paper materials.
From the above description, it is not difficult to see that the blade for die-cutting film surface materials is sharper and harder, so its service life is also shorter than that of die-cutting paper surface materials. Sometimes some knife mold manufacturers default to using a blade for die-cutting paper surface materials to make knife molds. This type of blade, due to its large angle and insufficient sharpness, will squeeze out the glue in the material, resulting in adhesive overflow. The generation of this kind of adhesive overflow has a process that is not obvious at the beginning, but becomes very obvious after a period of die-cutting. This is because the glue is gradually squeezed out during the die-cutting process. Some self-adhesive materials themselves are paper surface materials, but due to the thick coating or strong fluidity of the adhesive, using a blade with an angle of 52 ° is also more prone to adhesive overflow. In this case, it is recommended to use a blade with an angle of less than 42 ° for die-cutting. Now some knife mold suppliers have attempted to apply silicone oil coating on the blade, which can effectively reduce the residue of glue on the blade and also help prevent glue overflow.
B. overflow leaded by blunt cutting knife
Generally speaking, the service life of the blade for flat blade die-cutting ranges from tens of thousands to hundreds of thousands of times, while the service life of the blade for round blade die-cutting ranges from hundreds of thousands of times. However, no matter which type of tool is used for a long time, there will also be wear and tear. Once the die cutting tool is worn or dull, it may cause glue overflow. The overflow caused by this reason is often reflected at the local edge of the label. If the label is removed and observed against the light, it can be found that only local areas of the label have overflow, and the position of the overflow is relatively fixed. If you encounter such problems, just replace the blade in a timely manner.
C. overflow leaded by too high pressure
The die-cutting process is carried out under a certain pressure, and if the die-cutting pressure is suitable, the overflow phenomenon will not be particularly serious. If the die cutting blade is worn or the height of the round blade is not suitable, the operator will have to increase the die cutting pressure to produce normally, which can easily lead to label overflow. We know that the blade has a certain angle, and the deeper the cut, the greater the compression of the blade on the material, and the easier it is for the material to overflow.
In this case, it can be observed that the bottom paper of the die-cut label is not damaged, but there is adhesive overflow on the label, which can easily make operators mistakenly believe that it is caused by the raw material. However, the materials used are not thickened glue or highly mobile glue, leaving people confused about how to solve it. Therefore, when encountering this situation, you can try replacing it with a new knife to cut the mold and observe whether the overflow problem has been alleviated. If the overflow problem is alleviated after changing the tool, it should be a tool problem. For circular cutter die-cutting products, due to the high cost of the die-cutting tool, it cannot be easily replaced. If there are new tools with other patterns in hand, they can also be used for testing. If the new tool cuts without problems, it can also be judged as a tool problem.
D. The paper feeding of the die-cutting equipment is too long
During the die-cutting process, the material will pass through many guide rollers. Under the tension of the equipment itself, the guide rollers will have a squeezing effect on the material. If the die-cutting equipment takes a long paper path, it will also have a certain impact on the adhesive of the material. The adhesive will gradually become soft and have stronger fluidity during the continuous squeezing process. Therefore, for some raw materials that are prone to overflow, it is necessary to shorten the paper path as much as possible during die-cutting and reduce the number of materials passing through the guide rollers, which is more conducive to controlling overflow.
Some die-cutting equipment may have too many paper rollers or too much pressure, which can push glue out of the material. The squeezed glue will gradually accumulate on the paper guide roller, causing unstable operating tension of the equipment and possibly causing the material to be stuck and broken. Some printing equipment with excessive paper feeding often requires the material to pass through several sets of paper pressing traction rollers, in order to stabilize the material tension, but this also increases the risk of material overflow. Therefore, when using materials that are prone to adhesive overflow, it is necessary to shorten the paper path as much as possible. If the equipment itself is limited and cannot shorten the paper path, it can be considered to change the line die-cutting to offline die-cutting.
The above are some reasons and solutions that can easily cause mold cutting adhesive overflow. In the actual production process, in addition to the reasons listed in this article, there must be other reasons that lead to mold cutting adhesive overflow. Due to limited space, we will not list them all here. We hope this article can serve as a reference for more colleagues to share their valuable experience in controlling mold cutting glue overflow with everyone.
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