Static or not?
The most common statically charged printing materials are thermoplastics (plastics that harden when they reach a cold temperature, but reach a liquid state when they reach a hot temperature).
We can tell that a material is static in obvious ways, such as attracting dust, hair, and giving off small shocks, but this is not always the case. We found the following materials to have the most static problems:
- Polystyrene foam board;
- Polystyrene;
- PVC;
- Acrylic;
- Polycarbonate.
How does static electricity act in printing?
In printing, static affects print quality by causing a kind of reaction to the ink droplets. The result of static electricity in the impression caused by this phenomenon can be observed in the following ways:
• A fine mist of ink, usually visible between the printed and clear areas/edges, forming a blur. Sometimes, if done immediately, cleaning the surface can remove this mist.
• Larger volume ink drops forming a dotted line, usually in the direction of carriage movement, occur when negative ink pressure valves are left closed.
Media handling
Some suppliers offer media pre-treated or coated with anti-static corona treatment.
Please contact your supplier to determine availability. It is important that treated media are shipped within a reasonable time frame from corona treatment, as effectiveness will depend on this time. This ensures better adhesion, as well as optimizing printability and handling.
All printing material (and printer, if possible) should be located away from static-generating objects such as belt-fed presses and photocopiers. In particular, to avoid problems caused by static static electricity in print.
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Other important points
Static dissipative coating is also beneficial (it controls static energy caused by friction on the floor). A clean, dust-free area is always preferable, as any airborne particles will encounter the charged media surface. We recommend cleaning it thoroughly using alcohol or a 50% alcohol/water solution.
In addition to cleaning debris from the surface, generous application of alcohol and water greatly reduces the load on the site. Results are best when performed immediately before printing.
Cleaning can be done elsewhere, but when transported the printer may recover dust and static charge. After the media is placed on the table and cleaned with alcohol, if desired, wipe with an anti-static cloth or device.
Do not use anti-static sprays on media unless the application and printing are tested first, as these products may cause printed streaks or smears.
Humidity
Problems of static electricity in printing can be greatly reduced by an increase in the humidity of the printing environment.
Although most media print without difficulty at humidity levels between 25 and 50%, thermoplastics print most successfully when humidity is above 35%.
Some locations, such as desert areas, frequently experience very low humidity. While other regions only experience it at certain times of the year.
Trying to keep the temperature between 15°C and 38°C can make a difference. Too high a temperature can damage the ink and print head, and too low a temperature can cause the ink to freeze.
Adopt a humidity control system
If the printer is installed in areas with low humidity and/or a large volume of printed work generates static, we recommend installing a humidity control system.
With the system already installed, increasing the humidity in the printing environment is simple. If the location does not have humidity control or requires this care throughout the year, using portable humidifiers in the area may be sufficient.
Check the unit’s specifications to make sure it’s capable of the output required for the room size and current air changes. And if necessary, install more than one unit in close proximity to the printer to achieve the desired humidity.
Note that humidity levels are checked at or very close to the printer for better control.
Ionization method
A common method for controlling the static electricity in printing is the use of ionization. With an antistatic bar, positive and negative ions are created. They are then attracted to neutralize static and the ink does not suffer from dispersion problems.
It is important to note that the static electricity in printing it cannot be completely eliminated, only reduced. To eliminate it, something would have to be physically done to the material causing the static.
Ionizers come in many varieties, including rods, cloths, brushes, and pads. These devices should be attached to the printer itself, as they can provide an ideal surface for grounding. Cloths should be stored in their cases when not in use.
The most important aspect of all static reducing devices is proximity to the media surface and the time of printing.
Any effect obtained will be lost over time, so ionization must occur immediately, either before or during printing. Unless ionization is constant, the surface will recover its previously unbalanced state.
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