High flow-rate ink recirculation has also allowed for innovative machine design opportunities. Printheads utilizing this technology can jet in any orientation. Thus, some machines can be built more compactly—vertically rather than horizontally—while printheads continue to work in an extremely reliable manner. This capability opens up inkjet to a range of new applications, such as being used on a robotic arm to spray paint vehicles or printing beverage containers in an upright position at speed.
High-laydown technology
High laydown is a single-cycle print mode allowing for very efficient high pumping capacity of printheads. The same printhead can print both high-definition and high-laydown effects and textures, which is cost effective. High laydown enables a range of new applications, thanks to its ability to deposit large quantities of fluid in each pass.
High-laydown technology increases printhead productivity as much as five-fold. One printhead can jet up to 11 L (2.5 gal) per hour, printing very high amounts of ultraviolet (UV) inks or high-build varnishes in a single pass in any environment. The technology also delivers unprecedented ink discharge rates for gloss and adhesive effects on other materials, such as ceramic tiles, so effects can be printed at high speeds. This also aids in printing impressive solids for signs.
For additive 3D applications, high-laydown technology offers increased printing productivity (which significantly accelerates build rates for parts) as well as the ability to print a broader range of fluids, including higher-viscosity materials. This ultimately results in opening a wider range of applications to manufacturers and users than those printed with standard inkjet technology.
Ultra-high viscosity jetting capabilities
Historically, printheads have been limited to jetting materials with viscosities of 10 to 25 centipoise (cP). The combination of high flow-rate ink recirculation technology and high-laydown technology means fluids with significantly higher viscosities—up to 100 cP—can be jetted.
Ultra-high viscosity jetting introduces a wide range of new capabilities and applications for inkjet printing. For example, many inks—often more vibrant or just different in hues—are limited in use because the pigments suspended in the ink fluids are too large to effectively be jetted. The ability to lay down fluids with more particles or larger particle sizes offers increased colour gamut, opacity, and special effects. High-viscosity printing also allows the use of photopolymers with increased toughness and flexibility, which is very helpful for outdoor displays. Ultra-high viscosity capabilities enable jetting of a wider range of functional fluids used in glass applications, display panels, and even printed electronics.
The higher the flow rate, the greater the benefits
While ink recirculation is now commonplace, how it is implemented varies according to each manufacturer, because printhead architecture differs. Some printhead designs deliver inherent advantages when it comes to ink recirculation, while other designs are more limited. Consequently, end users will experience greater or fewer benefits of ink recirculation depending on which printhead design they are using. The two primary areas where ink recirculation varies by design are the recirculation flow rate and the proximity of recirculation to the rear of the nozzle. When a high flow rate passes immediately behind the nozzles, the result is interaction with the fluid in the nozzle itself. This interaction enhances the printhead productivity, reliability, and print quality.
Most importantly, these printheads can jet fluids recently considered impossible to work with. Inkjet is truly opening many applications to the industry as fluid viscosity becomes less of an impediment and more of an opportunity.
Graham Tweedale is general manager of Xaar’s printhead business unit, responsible for developing and supporting Xaar’s printhead business strategy. He has more than 20 years of experience across the Xaar business, including as chief operations officer (COO), director of engineering, and production manager. Tweedale can be reached via e-mail at graham.tweedale@xaar.com.
