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What is a print head and how does it work?


Every inkjet printer on the market has one thing in common: a print head. Small and large format inkjet printers all feature print heads that deposit ink on all of various types of media. Modern print heads contain chambers that get fed ink and tiny nozzles that spray out ink. Before print heads came around, prints were made on printing presses that made direct contact with the media. The process was often messy and expensive and the presses were very large. Modern print heads don't touch the media being printed on reducing mess and lowering the cost of printing. Inkjet print heads spray ink onto paper or other media in a controlled manner to produce the desired image. 

But how exactly do print heads work? Are all print heads created equal?

Though they all do the same basic job, not all print heads are the same. Different manufacturers use print heads with different technology. Currently, there are two main print head types, each using a different method for spraying ink. The two types are Piezo and Thermal. While both are drop-on-demand print heads, the ways they move ink into and out of the print head are different.

Piezo inkjet print heads are currently used in Epson inkjet printers including both their small format and large format printers. Piezo print heads don't use heat to force ink out of the nozzle. Instead, Piezo print heads feature a layer - usually a thin film – that is exposed to an electric charge that causes the film to vibrate. The vibration causes the film top flex and bend, building up pressure and forcing the ink from the nozzle onto the paper. Being able to quickly vibrate and flex the film allows for more precise control of how fast the ink gets pushed out of the nozzle.

Piezo print heads are compatible with a wide range of inks since they don't use heat in the printing process. Compatible inks include water-based, oil, eco-solvent and solvent based inks. A typical Piezo print head has 720 nozzles per color which can require multiple passes and may slow down printing speed. Piezo print heads can control the size of the ink droplet, which can increase print resolution in some applications when smaller droplet sizes are used. Piezo print heads have a longer lifespan and are designed to last for the life of the printer (generally around 3-5 years). Should the piezo print head need to replaced, it is more expensive and requires an authorized service technician.

Thermal inkjet print heads, currently used in Canon and HP inkjet printers, use heat and water-based inks for printing. Instead of using a membrane to build pressure and force ink out onto paper, heat is used to boil the ink and create an air bubble of ink vapor. The air bubble is then exploded as it's forced through the print heads nozzle. Once the ink is expelled, the chamber rapidly cools down and the process repeats. 

Thermal print heads are compatible with aquas or water-based inks. A typical thermal print head used in Canon plotters has 2,560 nozzles per color, with matte black having 5,120 nozzles because two matte black cartridges are required. Thermal print heads can wear out faster depending on how much printing is being down and on what type of media. Printers using thermal print heads have been designed for easy print head replacement and can be done by the user without a service call. Thermal print heads are less expensive to replace as well.

Depending on what you're going to be printing, it may be a good idea to look at the print head used in the plotter you're considering. Piezo print heads are used in plotters that print signs and banners because they can use solvent, eco-solvent and oil based inks. These inks are more durable for items that will be outside. If you are printing technical documents, presentations or posters that will be inside, then plotters using either print head will be suitable.

Large Document Solutions carries Canon, Epson and HP plotters in a wide range of sizes to suit any application. You can check out the selection on the plotter page of our website.