By Cassandra Balentine
Quality and speed advancements for wide format digital printers are driven by improvements in printhead technology.
“Competition at the print shop level has led to a need for expanded product offerings, which has in turn led to a higher demand in the performance of the printheads in wide format printers,” says Matt McCausland, product manager, professional imaging, Epson.
From drop placement and variability to automated maintenance functions, printheads continually evolve to drive better quality and productivity for print service providers (PSPs).
Improvements in both wide format hardware and ink depend on printhead engineering for success. “As printer manufacturers begin the hardware design process, many decisions are made based upon the capabilities of the included printhead,” shares McCausland.
New ink formulations drive market growth and expansion as well as innovation in printhead design. “It is impossible to consider advances in one without the other,” explains Dr. Ross R. Allen, senior technology specialist, inkjet technology platforms, HP, Inc. He says, for example, improvement in durability requires pigments, polymers, and other ink components that make these inks more difficult to eject reliably than simpler dye-based formulations. “Printheads and their service stations must handle these inks properly to produce consistent quality and reduce the impact on productivity from printhead maintenance.”
John Harman, business development manager, Ricoh Company Ltd., suggests that offering enhanced features such as including an ink recirculating structure in the printhead facilitates significant improvements in production uptime. This feature is also becoming increasingly critical with the use of heavier pigmentloaded inks and fast drying ink types including water and solvent.
Enabling the Future
Today’s PSPs are looking for speed, quality, and dependability. Printheads evolve to raise the bar on many of these demands.
“The evolution of single-pass printhead technology drives extreme advances and gains in productivity, efficiency, and profitability by increasing print speeds up to ten times over traditional inkjet print technology,” shares Kevin Shimamoto, GM, wide format, Memjet.
In fact, he explains that the productivity of a wide format printer with single-pass printhead technology rivals that of wide format LED printers. “Reprographic houses can now offer four-color printing without having to sacrifice the turnaround time for customer requests. This also leads to new revenue streams from market segments they cannot address with monochrome printing,” he offers. Applications like posters for retail environments is one example.
McCausland admits that every PSP wants high-speed, band-free printing. “Each iteration of printhead technology pushes that envelope in terms of what is possible. Innovations like variable-sized droplet technology and improvements to microweaves allow PSPs greater flexibility in product offerings and differentiation,” he offers.
Harman says increasing both the printhead resolution and the amount of ink the printhead can deliver efficiently, accurately, and consistently are key determinates in achieving higher resolution and speed. Also utilizing printheads with smaller drop volume have a significant impact on achieving high resolution and print quality.
Allen comments that virtually all large format inkjet printers offer printing resolutions of 1,200 dpi, which produces sharp text and smooth colors in graphics and images on a range of substrates. “Pushing resolution to higher levels doesn’t really improve quality, because 1,200 dpi already exceeds the resolving power of the human eye at a normal reading distance.”
He continues that what is more important to image quality is dot placement accuracy, dot size consistency, and precise color-to-color alignment to suppress artifacts such as banding and color fringing. “This requires a printhead with a robust and consistent drop ejection mechanism that delivers uniform-sized drop at uniform speeds across thousands of nozzles.”
“Once a printhead/ink combination meets an application’s needs for quality and productivity, it is the reliability of the inkjet writing system that has the greatest impact on a PSP’s day-to-day ability to deliver jobs profitability and on schedule,” explains Allen. It is important that printheads and their inks provide robust, high-quality printing or the PSP’s time and materials are wasted when jobs must be reworked due to streaks and banding. Furthermore, the cost of ink used to service the printheads affects cost per copy and service stations must be designed to use ink very sparingly. Inks, printheads, and the printhead service station work together as a system to ensure reliable printing performance, he adds.
Printhead malfunctions affect both productivity and operation costs. Proper maintenance is critical to ensuring they live up to their expected lifespan.
“The industrial inkjet printer market requires stable printing qualities—even under harsh environments—as inkjet printheads in the field are exposed to physical shock, chemical impact from various inks, and excessive heat cycles,” says Sumio Arima, senior manager, PD2 sales department, corporate printing device group, Kyocera Corporation. Printhead manufacturers must continually work to enhance robustness and long-term durability features to support these conditions.
According to Shimamoto, printhead life is influenced by factors such as maintenance, environmental cleanliness, ink formulations, and environmental factors like temperature and humidity.
McCausland sees continued maintenance as the single biggest factor in the life of a printhead. “For printheads that don’t burn out over time, it is important to make sure they are clean of any fibers, hairs, or debris. Oftentimes, print shops are not the cleanest environments, so I would recommend users be conscious of where they are placing the machine in their shop to limit external dust/debris generated from finishing equipment,” he says.
“All inkjet printheads—both piezo and thermal—have some wear-out process that requires printhead replacement after time in-service or liters of ink printed. Early failures may occur due to dry out, improper operating conditions in the printer, and mechanical damage from mishandling and paper misfeeds,” offers Allen.
Nozzle failures due to clogs, dried ink on the nozzle plate, and paper dust can often be recovered by printhead service cycles initiated by the operator or automatically. “Ideally, the printer manages the printheads to obtain the longest practical life,” suggests Allen. “A well-designed inkjet printer assures long life by calibrating energy to individual printheads and implementing automatic testing and servicing.”
According to Harman, the surest way to prolong the life of a printhead is to ensure that you look for features that include an ink recirculating structure in the printhead. “This built-in feature will go a long way to prolong the life of the printhead as well as improving daily operating performance. Following the OEM recommended cleaning and maintenance printer schedule will also ensure prolonged printhead life.
Ink is another important choice to preserving the life of a printhead. “Highquality inks jet better and are important for preventing printhead blockages. Using an improved ink can significantly extend the life of a printhead,” offers Greg Arnot, product manager, Xaar plc.
Print manufacturers in the wide format space continue to advance products to offer better quality, faster speeds, and more durability.
From a solvent perspective, McCausland says Epson printheads have gained notoriety for their ability to produce variable sized droplets, accurate fine text, and incredible image quality.
“Our new PrecisionCore TFP printheads are the latest in printhead technology from Epson,” says McCausland. They include 360 nozzles per channel and variable-sized droplet technology as small as 4.2 picoliters. Combined with Epson’s new Precision Dot microweave, the PrecisionCore TFP printheads included with the new Epson SureColor S-Series printers produce sellable quality prints at up to 550 square feet per hour, says McCausland.
In its latest line of SureColor S-Series solvent printers, Epson introduced an air filtration system and fabric wiping system to automate the maintenance process sand ensure reliable performance of printheads.
HP Thermal Inkjet printhead technology scales from scanning printheads less than an inch wide to deliver a single color of ink to four-color printheads 5.08 inches wide that are stacked together to make a 40-inch print bar. The company has the ability to tailor printhead and ink options to meet the specific needs of a large format printing application.
Allen explains that scanning printheads support a variety of large format applications, printing materials, and media sizes. Within its HP DesignJet line, PSPs can choose among a range of substrates including plain papers, photo glossy and matte papers, backlit films, canvas, heavyweight coated papers, vellums, and self-adhesive vinyl.
Stationary printheads span the width of the print medium using HP PageWide Technology, offering breakthrough levels of productivity and reduced printing costs— compared to LED printers—that allow a PSP to produce long runs on single, multiple roll machines that can potentially replace several scanning inkjet printers and LED electrophotographic printers, says Allen. HP PageWide XL printers print on rolls of bond paper, matte and satin poster papers, heavy weight coated paper, and matte polypropylene at speeds of up to 30 A1/ANSI D pages per minute.
With HP PageWide Technology, a stationary printhead with 202,672 total nozzles spans the width of the print and the print medium moves under the printhead at speeds of up to 75 feet per minute. A 5.08-inch HP 841 PageWide XL Printhead prints with four colors of HP PageWide XL pigment ink at 1,200 dpi with 6,336 nozzles per color. Eight of these printheads are used in the 40-inch, four-color printbar used in HP PageWide XL printers. They are individually launched into a printbar providing mechanical alignment and electrical and ink connections. Individually used printheads are easily removed and replaced by the operator within about a minute without tools, handling of ink, electrical connections, or manual alignment.
Kyocera offers a ceramic piezo-actuator, a core technology enabling the company to offer inkjet printheads with “worldclass” features, according to Arima. “Despite their long presence in the market, conventional wide format printers using solvent ink have not fully satisfied users. They require higher performance such as higher printing speeds and printing quality. They also need printers to achieve higher productivity. These needs are what Kyocera is focusing on. Achieving both enhanced printing performance and higher productivity would be the key for an inkjet printhead manufacturer like Kyocera to be a leader in the industrial market.”
“Memjet single-pass printing technology enables high resolutions at 1,600×1,600 dpi and fast printhead speeds with the most competitive total cost of ownership,” shares Shimamoto. He says Memjet continues to invest in its single-pass printhead technology with the intentions of advancing the market. He predicts future generations will increase print speeds, improve image quality, have better durability, and provide a better total cost of ownership.
Ricoh’s most recent developments are focused on incorporating an ink recirculating structure in its latest generation printheads. This feature facilitates easy priming, self-recovery from missing jets by injected air bubbles, prevention of ink particle sedimentation resulting in blocked nozzles, and prevention of drying out of water- and solvent-based inks in the nozzles.
“These benefits contribute to enhancing wide format printers’ productivity and increasing wide format printers’ confidence in consistently delivering highquality graphics,” explains Harman.
Arnot says printhead performance is improving across a number of areas. “At the high end, new devices like the Xaar 5601 offer high productivity with more than 5,000 nozzles in one printhead; in addition more than one color per printhead aids integration ease and printer setup. The Xaar 1201 printhead can use four colors per printhead.”
For the mid-range, Arnot points to eight-level grayscale, which allows RIPs to achieve much greater apparent resolution than the native resolution of the printhead. “Grayscale also allows better control of drop volume to help better tune ink volume to the media requirements.”
“Newer devices from Xaar offer much more flexibility and have the ability to jet more types of fluid. For example, the Xaar 1201 jets both solvent and aqueous inks. This allows it to fulfill the need for solvents in emerging global markets, but also allows the use of textile inks for soft signage graphics applications,” offers Arnot.
Demand for better, faster, and less expensive printheads never wavers, which means manufacturers continually innovate to propel markets forward.
The latest advancements in printhead technology enable PSPs to meet client needs and introduce new applications.
Mar2017, Digital Output