About Label Cold Stamping: Understanding These 10 Key Process Points Can Help You Avoid Production Pitfalls!

About Label Cold Stamping: Understanding These 10 Key Process Points Can Help You Avoid Production Pitfalls!

Cold stamping, as a post-printing finishing process, has been widely applied in narrow web printing. Often called the 'fifth color' of printing, cold stamping essentially combines printing and lamination techniques. Its working principle can be broken down into three steps: first, pre-coat the areas to be stamped with cold stamping adhesive via offset or flexographic printing; second, press the cold stamping foil onto the coated substrate to complete the transfer and peel-off process; finally, finish by rewinding the cold stamping foil and removing waste.

The cold stamping system mainly includes four modules: UV adhesive coating, cold stamping foil unwinding and lamination, UV curing of the adhesive, and cold stamping foil rewinding. The final stamping quality is influenced by multiple parameters across the production process, including adhesive coating thickness, substrate type, laminating roller hardness and pressure, UV curing power, stamping speed, rewinding tension, and peel-off angle. Therefore, comprehensive control is needed during production.

1. Control of Adhesive Amount on Anilox Roll

The amount of adhesive applied depends on the ink carried by the anilox roll. It should match the stamp pattern, substrate type, and production conditions. Rough substrates may require a higher adhesive coating. Incorrect adhesive settings can directly cause problems like plate smudging or pinholes in the stamping.

2. Flexographic Plate and Mounting Tape Selection

For cold stamping, choose UV-sensitive resin flexographic plates with a hardness range of 65°-70°. When selecting double-sided mounting tapes, consider the press model, stamp pattern, and plate thickness. Printing pressure should also be controlled carefully.

3. Substrate Selection

Most substrates suitable for flexographic printing can be used for flexographic cold stamping. For special substrates, pre-treatments like primers or corona treatment can improve adaptability. Avoid rough, uneven, or highly absorbent surfaces, as these can easily cause pinholes or poor transfer.

4. Control of Laminating Roller

There are three core points for the laminating process: first, roller hardness should be reasonable; silicone rollers with a Shore hardness of 90°-95° are recommended. Second, set proper pressure to avoid trapping air between the foil and substrate, preventing misaligned edges or pinholes. Third, ensure the roller surface is clean and free of debris. Improper hardness, surface damage, or incorrect pressure are common causes of poor transfer and incomplete patterns.

5. Control of Stamping Speed

Stamping speed should match the overall process conditions. Too slow affects foil transfer; too fast prevents the adhesive from fully curing. There's no universal speed standard; aim for the highest speed while maintaining quality and adjust according to the specific project.

6. Rewind and Unwind Tension Adjustment

Incorrect tension can cause wrinkles, delamination, or cracking in stamped patterns. Typically, rewind tension is set higher than unwind tension, and tension should be monitored throughout production.

7. Matching UV Curing Power

UV curing determines foil adhesion and scratch resistance of the product. Power must match stamping speed: the faster the speed, the higher the UV power needed. Dark-colored foils require higher curing power and may require slower production to ensure proper adhesion. Insufficient curing can lead to poor bonding and low scratch resistance.

8. Control of Workstation Spacing

Shorter distances between cold stamping workstations help maintain quality. A large gap between foil lamination and UV curing units can cause wrinkling, bubbles, or premature peeling. Under normal conditions, the distance should not exceed 1 meter.

9. Adhesive Quality Check

There are two key points: first, ensure the adhesive is within its shelf life; expired adhesives degrade performance and reduce foil transfer. Second, when processing special substrates, consult the adhesive supplier to confirm compatibility. Poor adhesive quality can prevent the foil from transferring entirely.