It’s rare for anyone to take the time to explain printhead technologies, which creates challenges for those who don’t know or understand them. When you know what the industrial inkjet printhead types and terms mean, you understand what it is best suited for and how it operates.
The following terms will describe various printhead technologies, their basic designs, and how they operate. Keep your eyes on some of the following technologies that double up on their operations like the piezo greyscale printhead.
Inkjet printheads that project an uninterrupted stream of ink droplets as long as the printer is operating use continuous inkjet printheads. Usually, there is only one nozzle per head, but multiple printheads may be utilized for wider printing platforms.
The ink stream gets deflected either away from or towards the media being printed on using either timed bursts of air or charged metal plates via an electrostatic field. Unused ink is captured, sometimes filtered, and then returned back to the ink storage tank. It’s efficient.
You will find CIJ printhead technology used for coding and marking over refined graphic printers.
Most modern inkjet printers use DoD printheads to create high-quality graphics. Wide format printers often use DoD technology. What is Dod?
Drop-on-Demand uses inkjet nozzles to generate and drop ink where needed to create a mark on the specific media. The term drop-on-demand is in contrast to continuous flow printheads. Drop-on-Demand heads fall under subcategories within the piezo-electric or thermal printheads.
Thermal printheads were the first DoD type printheads used in desktop inkjet printers in the early 1980s. These printheads are highly efficient, providing exponentially high-quality images and competitive printing speeds as compared with the piezo-electric printheads. The difference is that thermal technology works only with water-based inks and are restricted to indoor applications.
The concept of the thermal process involves the rapid heating of the printhead to the point of vaporizing liquid ink, which forms a bubble of gas that expands and then forces drops of ink out of a nozzle. The heating element shuts off, the bubble of gas cools down then condenses and contracts. The surface tension in the nozzle stops any air from getting drawn in, therefore more liquid ink is fed into the chamber.
You may hear this technology referred to as Bubble jet because of how this technology works.
Thermal stresses quickly wear out the heads. Thermal industrial inkjet printheads are designed as consumables that can cheaply and easily be replaced as needed.
Piezo-electric printheads are often referred to as simply piezo heads and are DoD heads that were introduced for large format printers during the 1990s. These heads virtually revolutionized the printhead market.
For the first time ever, UV-cured industrial inks and solvent could be printed digitally. This technology was originally used for screen process printing.
A crystal, usually a lead zirconate titanate, is how Piezo heads operate. The crystal contracts or expands when electrical current passes through the printhead. It’s this contraction or expansion that pumps in the ink chamber.
The crystals used with Piezo printheads are configured for shear or bend modes, which is a two-way expansion that either forces ink out of the chamber through a nozzle or draws the ink into the chamber.
Piezo printheads work well with any ink fluid and can be constructed for use with UV-cured inks, solvent-based inks, and aqueous inks. They are suitable for use with electro-conductive inks, large-particle and metallic inks, phase-changing inks, and 3D printing inks as well. Click here to buy industrial inks.
Piezo-electric printheads are more durable than thermal heads, but require more maintenance and care and cost considerably more than thermal printheads.
Other types of printheads are being developed, like the thermal PageWide for greyscale printing that is usually exclusive to Piezo heads and native resolution printheads for wide format inkjet printers.
Printhead technology is constantly evolving, keeping up with the needs and processes of industrial ink printing.