What Kind of Job is Possible

Under normal circumstances, any type of job that is printed on a flexographic machine may use the cold stamping process. However, the particular capabilities of the flexographic machine must be taken into account and for this the customer should contact his machine supplier. As mentioned in the cold stamping process description, the wet lamination technique requires a printing, laminating and stripping station. Using this new process it is possible to print halftones to full tones depending on the adhesive, substrate, anilox roller and printing plate used.

Adhesives for the Cold Stamping Process

There are numerous adhesives available in the market (see our process description). You must carefully test the suitability of the adhesive for your particular job. Manufacturers specifications should state that the adhesive

should be suitable for application over free radical UV curable inks/coatings in addition to be applicable over solvent based or water based inks.

What Kind of Substrates Can be Used ?

Practically all substrates that are processed on flexographic machines such as PP, PE and non-absorbent papers can accept cold stamping. If there are adhesion problems, the customer should contact the adhesive supplier.

The Anilox Roller:

Average Coating Weight of Adhesives Depending on the design to be applied to the substrate, the right anilox roller must be chosen. First start with 120 lines/cm and 10 cm3/m2. For fine detail work, the ceramic anilox should have higher line counts. For broad areas lower line counts are needed.

For all non-absorbent materials and plastics the typical coating weight should be in the range of around 2 to 5 g/m2. This calls for the anilox roller to be 180 lines/cm and 6 cm3/m2.

For more absorbent substrates, like paper, you should start with an anilox roller 100 lines/cm and 14 cm3/m2. However, we do not recommend that UV adhesive is applied directly to rough, untreated paper surfaces. On this type of material we suggest using a primer coating first.

Laminating Station

For application of cold stamping foil to wet UV adhesive, a silicone roller with 80 - 95 shore hardness is recommended. The tension of the foil unwinding and rewinding units should be as low as possible. Be careful, though, to avoid wrinkling. If you use a nip roller with too low a shore hardness, the result will be poor foil transfer. Both rollers used in the lamination process must be completely clean and particle free. Adequate pressure in the laminating station is important to avoid air entrapment. Trapped air results in poor foil transfer.

Suitable UV - Lamps

For UV curing, medium or high pressure mercury lamps should be used. The UV lamp output should be adjustable to take into account operating speed. The higher the speed, the more UV lamp output is required. Typical outputs are in the range of approximately 120 to 200 watts/cm. For colored cold foils, the UV lamp output must be set higher than for silver or light gold shades.

Distance between Printing Station, Stamping Unit, UV lamp and
Foil Release

All distances should be as short as possible in order to avoid wrinkling. There should be no idler rollers between lamination unit and foil release. In a typical configuration, the total distance between the printing unit and foil release should not be more than 1 m.

Typical printing and application speeds are between 45 and 120 m/min.