Today’s industrial printer market is broad and filled with diverse technologies. Global conglomerates like Videojet and Domino offer dozens of printer models, spanning from inkjet printers such as the Videojet 1000 and Domino G20i to high-resolution printers and thermal transfer overprinters (TTO). While these technologies mark substrates in unique ways, they all utilize printhead technology.
Printheads play a vital role in the marking process. In an industrial printer, ink is expelled from a printhead onto a substrate to create a digitally designed code or image without having to make direct surface contact. Through non-contact printing, coding systems can:
However, not all printheads are built with the same technology. There are a variety of printheads available with unique operating mechanisms and internal construction.
Below, we take a look at the vast printhead technology market and showcase some of the most popular models on the market.
For those unfamiliar with modern industrial printers, it’s important to understand that printheads come in different forms, including:
Because there are a variety of printhead technologies, it’s easy to become confused. These printhead types also frequently bear more than one of these terms in their product descriptions. For example, it isn’t uncommon to read about piezoelectric continuous printheads or drop-on-demand thermal printheads. Fortunately, these terms aren’t difficult to understand when they’re explained clearly.
First, let’s examine the difference between continuous inkjet and drop-on-demand printheads.
Two of the most commonly used types of industrial printers are continuous inkjet and drop-on-demand. The machines that fall into these two categories can be outfitted with different kinds of printheads. Some printheads utilize the same technology (e.g. piezoelectric printheads are compatible with both CIJ and certain DOD printers), while some printheads are exclusive to only one printer type (e.g. CIJ printers do not use any thermal printheads).
Since both printer types require printheads to operate, it’s important to understand the difference between these two printer categories before taking a deeper dive into printhead technology specifics.
Continuous inkjet printing utilizes a continuous flow of ink to mark materials. When a substrate passes by a CIJ printer, the machine’s printhead diverts a smaller stream of ink from the larger ink flow to launch a series of drops onto the material’s surface.
CIJ printheads complete this application through the use of electrostatic plates (see: piezoelectric printheads). All of the ink that was not expelled toward the substrate using these methods is redirected back to its source to keep the continuous flow circulating throughout the machine.
Drop-on-demand printing is an umbrella term that refers to various coding approaches that don’t use continuous ink streams to mark materials. Rather than diverting a stream of ink droplets from a continuously flowing ink source, DOD printers pressurize, create, and expel ink droplets only when a substrate approaches the machine.
DOD printers perform this application in a variety of ways. For example:
CIJ and DOD printers are fundamentally different machines that excel in their specific applications. Generally, CIJ printers are ideal for quick-moving production line setups, while DOD printers can perform a range of marking applications that differ based on the following DOD models:
To excel in these applications, each of these printer types is built with specific printheads. While certain printhead technologies are mutually exclusive to one kind of printer, others are shared between categories. By understanding the differences between CIJ printers and the various DOD machines, printhead terminology immediately becomes more descriptive.
For example, a continuous piezoelectric printhead is built for a CIJ printer that uses piezoelectric elements to oscillate ink drops. Similarly, thermal, thermal transfer, and DOD piezoelectric printheads provide insight into how a printhead will operate and what it is compatible with.
While it’s important to know how CIJ and DOD printers operate, it’s equally as important to understand the functions of each type of printhead. There are four major categories of modern printheads, including:
Here’s how each printhead technology works.
Piezoelectric printheads utilize electric charges to oscillate ink into individual droplets and drive them onto a substrate. These printheads are named after the piezoelectric elements located within them.
The concept behind piezoelectricity involves the relationship between electrical charges and the materials that they can manipulate. Every piezoelectric printhead is built with internal crystals that change shape when subjected to an electric shock. When the crystal deforms, it changes the direction of an attached vibration plate. As the crystal and vibration plate move together, they can create a series of clearly defined ink droplets and propel them out of a nozzle without the need for a heating element.
Ink-recirculating printheads such as the Xaar 1001 are a CIJ-compatible variation of the piezoelectric printhead and create a cleaner more, efficient ink stream.
When a CIJ printer is circulating ink but not actively printing on anything, the printhead’s nozzles can experience issues that hinder performance. For example, ink can dwell on the nozzles for an extended period, and this can lead to changes in the ink’s viscosity, temperature, and oxygen levels—elements that can negatively affect printing performance. Additionally, dust, debris, and air bubbles can enter the printhead, leading to clogged filters and blocked nozzles.
Ink-recirculating printheads prevent these problems by allowing the larger ink flow to continue moving at the back of the nozzle during the printing process. This keeps the nozzles in a constantly primed state and prevents the presence of dust, debris, and air bubbles within the larger ink stream.
Wide format printheads are another variation of the piezoelectric printhead and are ideal for creating high-resolution images on a large scale. Wide format printheads, which are made by companies like Mimaki and Memjet, can utilize multiple piezoelectric elements and tens of thousands of nozzles to create impressively large images at 1500+ dpi.
As the name suggests, thermal printheads mark substrates through heat application. Within each thermal printhead is a series of heating elements that come into contact with the ink source. The functionality of these printheads depends on what type of printer they are used with.
A thermal inkjet printhead applies heat to a liquid ink-filled cartridge. The heating elements increase the temperature of the ink to create an air bubble. As this bubble expands, it launches individual droplets from the printer’s nozzle and onto the substrate. Once the droplets are expelled from the nozzle, the bubble collapses. The bubble’s absence causes a vacuum effect to occur, allowing the printer to immediately repeat the marking process.
In thermal transfer overprinters, the thermal printhead doesn’t come into contact with liquid ink. Instead, it applies heat to an ink-covered ribbon to melt the ribbon’s coating. Directly beneath the ribbon is a substrate. By melting the ribbon’s outer ink coating, the thermal printhead can create a clear image on the substrate that is completely dry once it emerges from the printer.
Printheads enable industrial printers to mark substrates with a high degree of speed and accuracy. Like other elements of industrial printing, they are also constantly evolving. In just the past year, advancements like auto-retracting nozzles and self-cleaning elements have allowed printheads to operate with more efficiency than ever before.
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