What should be done if white edges appear in the die-cutting of laminated paper?

Practical methods and suggestions for solving the problem of white edges in film die-cutting

In the printing and packaging industry, the die-cutting process after lamination has a significant impact on the final effect of the product. However, many enterprises encounter the problem of white edges on the edges of laminated paper products after die-cutting. This not only affects the appearance but may also cause dissatisfaction among customers and result in losses. The white edge phenomenon is essentially due to the insufficient bonding force between the film and the paper to withstand the impact during die-cutting, resulting in edge separation. To improve this problem, systematic adjustments need to be made from multiple links.

I. Analysis of Common Causes of White Border Issues

Understanding the specific causes of white borders is the basis for formulating corresponding countermeasures. White edges are mainly caused by the separation of the film and paper at the cut edge during die-cutting, and are usually related to the following factors:

The status of the die-cutting knife

Die-cutting knives with insufficiently sharp edges rely more on extrusion rather than cutting through the material during processing, which can easily generate significant stress and cause the film to separate from the paper. In addition, if the height of the knife line is inappropriate or there are problems with the padding, it can also cause uneven cuts and pulling.

Lamination process control

Insufficient adhesion of the film coating is one of the common causes of white edges. If the performance of the film or glue used is insufficient, or if the parameters such as temperature, pressure and speed during lamination are improperly set, it will affect the full integration of the glue and the paper. If the surface of the paper is too smooth, has powder spraying or has an inappropriate moisture content, it will also weaken the bonding effect.

Material and environmental adaptability

Paper and film respond differently to environmental temperature and humidity. If the storage environment changes significantly after lamination, internal stress may form, making it easier for the material to separate from the edge during die-cutting. In a cooler environment, glue becomes brittle, loses its toughness and is more prone to tearing.

Ii. Systematic Methods for Improving White Edges

To address the issue of white edges in film die-cutting, improvements can be made from multiple aspects such as die-cutting tools, process control, and on-site operations.

Selection and maintenance of die-cutting tools

Select die-cutting blades with sharp edges and regularly inspect and replace them to ensure the quality of the cut. Select an appropriate knife type based on the thickness of the material. For instance, a straight knife usually performs well in reducing fuzzing.

In terms of supporting tools, appropriate knife plate spring pads and indentation strips can help optimize the force distribution during die-cutting. Some enterprises have optimized the elastic parameters by customizing the spring pads of the die-cutting plates, which not only extends the service life of the die-cutting molds but also reduces the frequency of downtime for replacement.

For the die-cutting requirements of different materials, suitable supporting materials can be selected. For instance, pharmaceutical packaging has high requirements for cleanliness, and silicone oil backing paper that meets food contact requirements can be used. For precision packaging of electronic products, a relatively hard reverse pressure line can be used in combination to control the depth of the indentation.

Key Points of process control

Strictly control the temperature, pressure and speed parameters of lamination to maintain a stable environment in the lamination workshop. It is recommended that the temperature be controlled at 23±2°C and the humidity be kept at around 50%±5%.

Before mass production, it is recommended to conduct small sample tests first to confirm the compatibility of paper and film and avoid quality problems caused by material mismatch.

Iii. On-site Adjustment and Emergency Measures

If white edges appear during the production process, the following methods can be tried for temporary adjustment:

Increase the ambient temperature appropriately

Local heating of the die-cutting area is one of the common methods. Infrared heating plates or hot air guns can be used to raise the material temperature to 25-30°C, enhancing the toughness of the film and adhesive layer.

Adjust the die-cutting parameters

Under the premise of ensuring thorough cutting, appropriately reduce the die-cutting pressure. Check and replace the gasket. Using a slightly softer new gasket can provide some cushioning.

Optimize the Angle of waste discharge

Adjusting the waste discharge Angle between 40 and 60 degrees can help reduce the pulling on the product edges, thereby minimizing the formation of white edges.

Contact information for Shenhua Printing Materials: Mr. Ji, 19924506937