Adhesive materials breaking during waste discharge? These reasons should not be ignored!

It is relatively common for the waste edge of self-adhesive materials to break during die-cutting. Once a break occurs, operators have to stop the machine to reorganize the waste edge, which in turn leads to reduced production efficiency and increased raw material waste. So, what are the causes of waste edge breakage in self-adhesive material die-cutting, and how should one deal with it?



01 Low tensile strength of the material itself causing waste edge breakage



Some materials, such as coated paper (also known as glossy coated paper), have shorter paper fibers and are relatively fragile. During the die-cutting waste removal process, the tensile strength of the waste edge is lower than the tension imposed by the equipment, making it easy to break.

In such cases, it is necessary to minimize the equipment's waste removal tension as much as possible. If the equipment's waste removal tension has already been set to the lowest level but the problem persists, then during the preliminary process design stage, the waste edge should be designed wider to ensure that waste edge breakage does not occur frequently during die-cutting.



02 Unreasonable process design / overly narrow waste edge causing breakage



Many labels used for variable information printing on the market come with easy-tear dotted cut lines. Some self-adhesive label processing companies, due to equipment limitations, have to place the dotted cut and border cut on the same die-cutting station. Additionally, due to cost and price considerations, the waste edge is designed very narrow, usually only 1 mm wide. This die-cutting process demands a lot from the label material, and a small mistake can easily cause waste edge breakage, thereby affecting production efficiency.

It is suggested that self-adhesive label processing companies, whenever possible, separate the easy-tear dotted cut lines and label borders during die-cutting. This not only reduces the frequency of waste edge breakage but can also greatly increase die-cutting speed. For companies that cannot do this, adjusting the proportion of the dotted cut or removing the part of the dotted cut that extends beyond the label border can resolve this problem.



03 Raw material defects causing waste edge breakage



Breaks in the self-adhesive material can also easily cause waste edge breakage. This problem is relatively easy to identify and will not be elaborated here. However, note that some self-adhesive materials have very small edge defects that are not easily visible and require careful inspection to detect. When such problems occur, removing the defective material before die-cutting is sufficient.



04 Excessive adhesive fluidity or too much adhesive coating causing waste edge breakage



The amount of adhesive coating on self-adhesive materials significantly affects their die-cutting performance. Generally, on die-cutting equipment, self-adhesive materials are not immediately discarded after die-cutting; they must continue to be conveyed forward for a certain distance before reaching the waste removal station. If the adhesive is applied too thickly, during the transfer from the die-cutting station to the waste removal station, the adhesive may flow back, causing previously cut self-adhesive facestock to stick together. This results in the waste edge breaking when pulled due to adhesion.

Generally, the coating amount of water-based acrylic adhesives should be between 18–22 g/m², while hot melt adhesives should be between 15–18 g/m². Exceeding these ranges greatly increases the likelihood of waste edge breakage. Even if the adhesive coating is not excessive, adhesives with high fluidity can easily cause waste adhesion and subsequent edge breakage.

When encountering such problems, you can first observe whether there is a relatively severe stringing phenomenon between the waste edge and the label. If the stringing is relatively severe, it indicates that the adhesive amount is large or its fluidity is strong. This issue can be resolved by applying some silicone oil additive to the die or by heating with an electric heating rod. Silicone oil additive can effectively slow down the backflow of the adhesive, while heating the self-adhesive material can quickly soften the adhesive, thereby reducing the degree of stringing.

05 Die tool defects leading to waste edge breakage

Defective die tools can also easily cause waste edge breakage. For example, small notches on the blade edge can prevent the adhesive face material from being completely cut through. The uncut portion experiences more concentrated stress compared to other parts, making it more prone to breakage. This phenomenon is relatively easy to determine because the location of the break is fixed. In such cases, the damaged die should first be repaired before being used for die-cutting.