In label printing, laminating is a critical process to protect ink, enhance gloss, and improve durability. However, issues such as bubbles, impurities, and curling that occur after laminating often affect product quality and production efficiency. This article systematically analyzes the root causes of these common problems and provides practical solutions.

1. Film-encapsulated bubbles: cause analysis and troubleshooting

Bubble-laden films not only compromise aesthetics but may also compromise label protection efficacy. The primary causes can be categorized into three types:

1. Defects in film raw materials

Some thin films may contain microbubbles in their pre-applied hot melt adhesive layer during factory release. This constitutes a raw material quality issue. The primary solution involves enhancing incoming material inspection and post-machine inspection during production to promptly identify and replace defective batches.

2. The surface of the labeled material is uneven.

If the surface of the printed self-adhesive material is uneven, the film cannot adhere completely during lamination, resulting in bubble formation. The causes of unevenness include:

Material defects: The base paper or surface material has uneven spots.

Printing process issues: Foreign objects on the equipment's pressure roller cause material indentation; or localized excessive ink accumulation.

Solution: Observe whether the bubbles exhibit regular patterns from different angles and inspect whether the label material at the corresponding position is flat. After identifying the root cause, cleaning the roller or adjusting the printing process will resolve the issue.

3. Aging of Rollers in Coating Equipment

If the pressure roller of the film laminator ages, deforms, or suffers surface damage due to prolonged use, it will fail to provide uniform and sufficient pressure, resulting in poor adhesion between the film and label and the formation of bubbles. Regular inspection and replacement of aged pressure rollers are fundamental preventive measures.

II. Contaminants in Film Lamination: Controlling Workshop Environment and Static Electricity at Source

The "white spots" or impurities under the coating layer are mostly caused by dust and paper powder in the environment being pressed into the film.

1. Material Cleaning and Pretreatment

Dust removal procedure: Before loading, the material surface should be cleaned with dust removal cloth or a special low-adhesive dust removal roller to remove dust and paper fibers.

For paper handling: When dealing with papers exhibiting poor surface strength and prone to powder shedding, applying a primer ink or diluent layer prior to printing graphics can solidify surface fibers. This significantly reduces paper powder detachment, thereby establishing a foundation for high-quality laminating.

2. Workshop Environment and Humidity Control

Environmental cleanliness: Maintaining a clean printing workshop is crucial. Shoes must be changed before entering, and the floor should be mopped regularly to minimize dust sources.

Static Control: Printing film materials are highly prone to generating static electricity, which can attract airborne dust. Maintaining the relative humidity in the workshop at 50%-60% is an effective method for suppressing static electricity. Industrial humidifiers can be used, or humidity can be increased by regularly mopping the floor.

III. Film Wrapping Curling: The Key to Precise Tension Control

The main reason for the label curling toward the face material or base paper after coating is the mismatch between the film tension and the label material.

1. Principle of Tension Adjustment

Upward curl (toward the surface): This typically indicates excessive tension in the film, requiring adjustment.

Roll down (toward the bottom of the sheet): This usually indicates insufficient tension in the film, requiring adjustment.

2. Dynamic Adjustment and Equipment Selection

The tension of the film is not constant in the uncoiling process: the tension is high at the core and low at the opening. Therefore, the tension should be adjusted dynamically during operation, increasing it appropriately when uncoiling and decreasing it when approaching the core.

Simple inspection method: After film coating, cut off several labels of finished product size, peel them off from the base paper, and place them flat on the table for observation. If they are flat, the tension is appropriate; if curled, adjust according to the aforementioned principles.

The importance of equipment: The tension adjustment range of film-coating units in older equipment is often limited. Modern printing presses mostly adopt servo motor control for tension adjustment, which is more precise and convenient, fundamentally reducing such issues.

We hope this systematic troubleshooting guide proves helpful. Selecting suppliers with stable processes and modern production equipment is fundamental to achieving flawless laminated labels. Should you have any specific questions regarding label production, please feel free to contact us.