Die cutting is an important process in the production of adhesive labels. During the die cutting process of adhesive labels, we often encounter some problems that can greatly reduce production efficiency and even lead to the scrapping of entire batches of products, causing huge losses to enterprises. In this article, we want to share with you some common problems and solutions of adhesive labels in the die cutting process.
Some labels are designed to bleed through the cut, which requires the cutting blade to cut where there is ink. In this case, the ink on the cut area of the label often comes off after die cutting. If the bleeding cut is on a laminated product, the film may also come off with the ink. There are two main factors that cause this phenomenon:
Low surface energy of the material
The adhesion of the printing material surface, also known as the surface energy of the printing material, generally should not be less than 38 dyne to allow the ink to adhere to the material surface. If good ink adhesion is required, the surface energy of the material should be at least 42 dyne, otherwise, ink peeling will occur. If the material surface energy is lower than 38 dyne, the ink cannot be firmly attached after printing, and then bleed cutting can easily lead to the ink peeling off at the die cutting edge.
In this case, the material can be replaced or a layer of bottom ink can be printed on the material surface to increase its surface tension and ensure that the ink does not peel off during label die cutting.
Insufficient ink adhesion
Some ink has quality problems or does not match the printing material, which may lead to insufficient adhesion of the ink after printing. In this case, ink can easily come off from the die cutting edge when the label is printed and bleed cut.
Therefore, it is recommended that printing factories conduct tape testing on samples produced before mass production. If the test results meet the standards, then mass production can be carried out. If the adhesion of the ink is insufficient, the ink can be replaced to solve this problem.
There are two common ways of receiving adhesive labels: roll packaging and sheet packaging, and sheet packaging requires cutting of the adhesive material. Usually, the Glascine bottom paper used for sheet packaging has a thicker paper base with a weight of more than 95g. However, sometimes thinner Glascine bottom paper needs to be cut into single sheets, which may lead to the problem of material curl after receiving.
The main reason for the curling of Glascine base paper material after cutting is that the water content of the material base paper will change drastically due to environmental influences. The change of water content will cause sharp shrinkage or expansion of the paper. As the adhesive material is a composite material, the shrinkage of the base paper and the surface material is different, and the deformation rate of the base paper and the surface material under the influence of humidity changes will also be different. If the base paper shrinkage is less than the surface material shrinkage, then the Glascine bottom paper material will curl upward, otherwise it will curl downward.
Once this problem occurs, it is important to control the humidity of the production workshop, allowing the relative humidity of the production workshop to remain between 50% and 60%. This is a moderate humidity range that can mitigate the deformation of the material. If the material has already undergone deformation, a simple baffle can be placed at the paper outlet of the die cutting machine to raise the outlet position so that the material can be properly collected and then sorted out.
Excessive static electricity during the die cutting process can cause the labels to stick together. This phenomenon mainly occurs in the cutting of single-sheet products. When encountering such problems, we can try the following two methods to solve them:
Install an anti-static device on the die cutting machine
Currently, common anti-static devices for die cutting machines include anti-static rods and ion air guns. For some older die cutting equipment, if an anti-static device is not available, an anti-static copper wire can be used to solve the problem.
Increase the relative humidity in the workshop
An increase in workshop humidity can help eliminate static electricity. Companies with conditions can install an automatic humidification system in the workshop to maintain workshop humidity. Alternatively, industrial humidifiers can be used for humidification. Companies without conditions can increase humidity in the workshop through multiple floor cleaning. For materials that are particularly prone to static electricity, a humidifier can be placed next to the machine to locally increase humidity and eliminate static electricity.
