Maintenance Tips for Light Sources and Accessories in UV Printing
Using UV ink or UV varnish may cause the printing ink rollers, blanket or tree-shaped plates to swell. Severe swelling can lead to peeling or surface cracking. Therefore, it is very important to use the specified rubber and tree-shaped plates.
Many UV inks suppliers will recommend a usage range. For instance, materials such as rubberized nitrocellulose or butadiene nitrocellulose treated with these processes can be compatible with oil-based UV inks and varnish; while natural rubber and polyethylene materials will expand and are not suitable for UV inks and varnish; EPDM rubber is particularly suitable for UV inks and varnish, but not for general oil-based inks. The selection of ink rollers for the printing machine also follows this principle. It is not advisable to frequently switch between UV inks and general oil-based inks. If a change is necessary, the ink rollers must be cleaned thoroughly to remove all residual chemicals.
When installing UV lamps, the type of printing machine needs to be taken into consideration. For BASF's UV inks and varnishes, either industrial pressure mercury lamps or microwave H bulbs are used. If the first one is monochrome, two 120w/cm medium-pressure mercury lamps should be used. Generally, the difficulty of drying the four-color UV inks increases in the order of magenta, yellow, cyan, and black. Therefore, the sequence for UV color printing should be black, cyan, yellow, and magenta.
Some color combinations are extremely difficult to achieve, such as green which is made by blending yellow and cyan; moreover, the blending of opaque colors is also very challenging as it reflects all the UV light back. The same issue applies to metallic colors, gold, and silver.
The lifespan of UV mercury lamps is fixed. Over-aged lamp tubes cannot dry UV inks or varnishes. The instructions for UV lamps usually indicate that after approximately 1,000 hours of use, the UV lamp must be replaced. In actual production, if you find that the printed materials cannot be dried under normal printing speed, you must consider replacing the UV lamp.
If a reflector hood is not installed, approximately 80% of the U.V. light will be diffused and unable to reach the printed material. Therefore, the UV lamp must be equipped with a lamp hood to reflect and focus the light on the direction of the printed material. Additionally, the reflector hood must be cleaned and maintained at all times. Some paper dust or powder spray dust that adheres to the reflector hood will affect the reflection efficiency of the UV lamp; if the UV lamp is not used for a long time, the UV lamp hood should be closed to prevent dust from entering.