If you are using thermal inkjet printers to print on packaging films, you might have encountered some problems with your thermal inkjet (TIJ) printing that are caused by static electricity.
Static electricity is the result of an imbalance of electric charges on the surface of an object, such as a plastic film. When two objects with different electric charges come into contact and then separate, they can create a spark or shock called an electrostatic discharge (ESD).
ESD can damage the delicate nozzles of your thermal inkjet printhead, affect the quality of your print, and even pose a fire hazard in some circumstances.
This article will explain how static electricity is generated, how it affects thermal inkjet printing, and how you can prevent or reduce it – hopefully solving some mysterious print problems.
How Static Electricity is Generated
Static electricity is more likely to occur when the air is dry, and the humidity is low. This is because water molecules in the air can help to neutralize the electric charges on the surface of objects. When the air is dry, there are fewer water molecules to conduct the electric charges, and they can build up more quickly.
Static electricity can also be generated by friction, which is the rubbing of two objects against each other. For example, when you peel off a plastic film from a roll, you are creating friction between the film and the roll. This can cause the film to become positively charged and the roll to become negatively charged. The same thing can happen as the film travels through the rollers and sections of the packaging machine.
How Static Electricity Affects Thermal Inkjet Printing
Static electricity can cause several problems for thermal inkjet printing, such as:
- Dust attraction: A charged film can attract dust and lint from the air or the surrounding environment. This can cause print defects, such as spots, streaks, or smudges. It can also clog the tiny nozzles of the printer, reducing the ink flow and the print quality.
- Ink misplacement: A charged film can also affect the ink droplets ejected from the printer. The ink droplets are also electrically charged and can be attracted or repelled by the film, depending on the polarity of the charges. This can cause the ink to land on the wrong location or to spread or splatter on the film, resulting in poor print resolution and accuracy.
- Printhead damage: A charged film can also damage the printhead itself, especially the area around the nozzles. In some cases, the print cartridge might need to be replaced before all the ink is used.
- Fire hazard: A charged film can also pose a fire hazard, especially if the film is flammable or there are combustible materials nearby. An ESD can ignite the film or other materials, causing a fire or an explosion.
How to Prevent or Reduce Static Electricity
To prevent or reduce static electricity, you need to control the humidity, the friction, and the charge of the film. Here are some ideas to do that:
Increase the humidity: An industrial humidifier can increase the moisture level in the air, which can help dissipate the film’s electric charges. The recommended relative humidity for thermal inkjet printing is between 40% and 60%. You can use a hygrometer to measure the humidity in your printing area and adjust the humidifier accordingly.
Install a static bar or ionizer: An ionizer can emit positive and negative ions into the air, neutralizing the film’s electric charges. Depending on where the static electricity is most problematic, you can place the ionizer near the printer for the best results. You should also keep the ionizer clean and well-maintained and follow the safety precautions of the manufacturer.
Use a grounding device: A grounding device can provide a path for the electric charges to flow from the film to the earth, which can eliminate static electricity. You can use a grounding wire, a grounding rod, or a grounding mat, depending on the configuration of your printer and your film. You should make sure that the grounding device is installed correctly and connected and that there is no resistance or interruption in the circuit.
Static electricity can be a nuisance for thermal inkjet printing, but it can be prevented or reduced with some simple measures. By controlling the humidity, the friction, and the charge of the film, you can improve the performance and the quality of your printer and your print, and avoid the risks of printer damage and fire hazard. We hope this article has helped you to understand how static electricity can affect thermal inkjet printing, and how you can deal with it. Happy printing!
Article on static control in packaging from Simco-ion
How to avoid printer damage by static electricity from Kao Collins