By Melissa Donovan
Improvements in printhead design drive the industry forward. Wide format printers deliver productivity as well as efficiency, and the printheads found under the hood help achieve this. Two categories of printheads are used in wide format printing—piezoelectric and thermal. Manufacturers are devout when it comes to researching how to prolong the life of both types of printheads with the goal of creating a number of robust products that can even withstand entry into the printing of industrial-type applications.
Advancing Wide Format
Printhead technology directly affects the advancement of wide format digital printing. The newest iterations give print service providers (PSPs) more flexibility in terms of time, cost, and services offered.
It’s a symbiotic relationship. “PSPs look for expanded product offerings, which leads to a higher demand in the performance of the printheads in wide format printers,” says Matt McCausland, product manager, professional imaging, Epson.
“High-quality images are achieved from less passes, using various ink types, using only two to four printheads, and all at faster speeds giving more throughput. It’s like a second digital revolution has been kick started by piezoelectric inkjet silicon MicroElectroMechanical Systems (MEMS) technology,” explains Simon Kirk, senior product manager, Xaar plc.
Fujifilm North America Corporation defines silicon MEMS (Si-MEMS) as a proprietary fabrication technology based on semiconductor manufacturing techniques. According to the company, this technology combines with drop on demand piezoelectric micro-fluidic pumping in a single monolithic structure with sub-micron accuracy.
John Harman, business development manager, industrial inkjet, Ricoh Company Ltd., points specifically to Ricoh’s addition of flow-through capability, which provides advancements in heightened serviceability for wide format printers, resulting in increased productivity.
Prolonging the Printhead
A printhead should be developed with a long lasting timeframe in mind. Manufacturers focus on specific materials like steel to provide a level of indestructability. On the other side of the spectrum, PSPs need to be apprised of proper upkeep to maintain the level of performance expected of the printhead.
“Manufacturers have focused on printhead robustness over the past few years,” admits Esteban Marin, director – Printek division, Seiko Instruments USA, Inc. Improvements in chemical compatibility are catching up with the increasing amount of new ink formulations. Robust build materials are used to match the industrial requirements of wide format machines.
One example of a robust build material is a stainless steel printhead construction with a robust metal nozzle plate, according to Harman. “These are increasingly critical for prolonged printhead life as there are significant increases in wide format print volumes,” he continues.
“Advancements in the process for manufacturing thermal inkjet printheads allow for a much larger number of print nozzles on a printhead than in the past. The overall cost per nozzle is very small and nozzle redundancy can therefore easily be implemented prolonging the overall life of the printhead and increasing the image quality,” shares Gianluigi Rankin, director product marketing, Memjet.
Once on a shop floor, printheads must be monitored by the PSP. “A good maintenance station that includes capping, automated cleaning, and spitting areas ensures you can cater to all the requirements of a printhead—purging, clearing of nozzles, and maintenance of the meniscus. Also, working with a reputable and capable integrator will make all the difference in how the printhead is managed, maintained, and run so you can optimize printhead life,” shares Kirk.
“The biggest factor in the life of a printhead is continued maintenance—it is important to make sure they are clean of any fibers, hair, or debris. Print shops are oftentimes not the neatest environments, so it is important to be conscious of where a printer is placed in the shop to limit external dust/debris generated from finishing equipment,” agrees McCausland.
Besides continued maintenance, using the correct ink can ensure the life of a printhead. “Ink definitely plays a factor. Inkjet ink is a highly engineered product and a small change to the formulation of the ink for a thermal inkjet can have a significant impact on the life of the printhead. That change can alter the way the ink reacts with the inkjet chamber and heating element, and reduce the overall printhead life,” says Rankin.
“As a general principle, the longest printhead life will be obtained when printheads and ink are store, handled, and used in accordance with the manufacturer’s guidelines and use by dates, and when equipment is maintained and operated according to recommended practices and maintenance schedules in the operator and service manuals,” recommends Dr. Ross Allen, senior technical specialist, inkjet technology platforms, HP, Inc.
Quality and Productivity
Features that print providers expect from their print engine include high image quality and productivity at low running costs. Printheads contribute to this.
“Each evolution of printhead technology pushes the envelope in terms of what is possible. Innovations like variable-sized droplet technology and improvements to micro-weaves allow print providers greater flexibility in product offerings and differentiation,” explains McCausland.
According to Kirk, the technology found in the Xaar 1201 printhead is an excellent example of achieving both quality and productivity. The Si-MEMS architecture in this particular printhead enables all 1,280 nozzles to fire 2.5 picoliters at eight gray levels, up to 30 kHz, achieving 1,200 dpi or higher from a low number of passes. “This combination of features, enabled by Si-MEMS technology, gives high-resolution images at high speed on multiple substrate types,” he continues.
“As a printhead manufacturer incorporating features including flow through, higher jetting frequencies, and higher temperature handling capabilities will increase the bandwidth for the OEM printer manufacturer to deliver higher image quality and increased productivity at lower running costs,” shares Harman.
Allen adds that a printhead offering low cost per nozzle can employ more nozzles to achieve higher productivity as well as feature nozzle redundancy, which hides nozzle errors.
Response to Industrial
With the advent of industrial-type applications, printheads need to be even more robust. Printhead manufacturers respond to this in their own individual ways.
Epson believes robustness is the inherent benefit of its PrecisionCore thin film piezo (TFP) printhead technology. It has the ability to run a variety of different ink chemistries through the printheads with high reliability and consistency.
Inks used in HP PageWide printers are formulated for longer decap times, or exposure to air without printing. This directly contributes to printhead robustness. “Inside the printhead, inks are circulated to keep them fresh in the drop generators between printing drops. This feature, called microcircluation, is enabled by the high density of active elements provided by HP Thermal Inkjet technology,” explains Allen.
“At Memjet, we have drawn from our past experience in applications like corrugated board and commercial printing and made improvements that make our printhead technology even better suited for a lot of industrial applications. We see a lot of interest from companies outside of our current market segments,” shares Rankin.
Ricoh addresses the advent of industrial applications with its stainless steel printhead construction. In addition, printhead flow-through capabilities enable a more robust industrial print solution, according to Harman.
Seiko creates its printheads so they are capable of sustaining the harshest environments. Some of the most recent developments in printhead manufacturing include integrating stronger materials for the nozzle plate and water-resistant printhead designs. Both are in response to industrial applications.
At Xaar, the company focuses on three primary features of its Xaar 1201 printhead to ensure its robustness holds up in varied printing environments. A nozzle guard surrounds the nozzle plate and ensures protection from low-level media crashes. The printhead is cable of jetting solvent, eco-solvent, aqueous, or UV ink. An elevated electrical connection cover protects the electrical connection from ink splashes.
Printheads for Sale
Here are some of the newest printheads or advancements to existing models in the wide format space. These include both piezoelectric and thermal technologies.
Epson PrecisionCore TFP printheads include 360 nozzles per channel and variable-sized droplet technology as small as 4.2 picoliters. They are compatible with aqueous, solvent, resin, and UV-curable ink types. The technology scales from Epson’s desktop devices to its wide format printers and label presses.
Fujifilm Dimatix’s Samba GMA is a compact, low voltage, full Si-MEMS printhead designed for scanning applications such as textile, indoor signage, soft signage, and high-quality UV printing. With 384 individually addressable nozzles, the Samba GMA 33 printhead features a native 300 dpi resolution and a native ink drop size of five picoliters delivering outstanding print quality that jets a range of fluids including UV-curable, solvent, and aqueous inks.
HP offers a 4.25-inch printhead that powers its HP PageWide presses and HP Latex 1500 and 3000 Series printers. The standard version of the printhead has 10,560 single drop weight nozzles, while the HDNA version features 21,120 nozzles with 10,560 each of low and high drop weights. The printhead uses five HP Thermal Inkjet chips in a staggered and overlapping configuration to produce the 4.25-inch print swath.
Memjet’s new DuraLink technology uses aqueous pigment inks for higher durability prints. The product promotes a longer printhead life as well. The DuraLink printhead features a 1,600 dpi native resolution, 8.77-inch width, 70,400 nozzles, and five times nozzle redundancy. It produces 2.2 picoliters drops up to the recommended maximum nozzle firing frequency of 15.5 kHz.
Ricoh MH5421 F/MF printheads are an extension of the MH5420 family. They offer printhead flow-through capability for both high and low viscosity inks. This enables improved handling of heavy loaded inks and improved control of ink jetting temperatures. In addition, the company recently launched the MH5421 to offer improved compatibility with aqueous ink.
Seiko offers the RC1536, its latest recirculation printhead, which sets standards for new developments capable of jetting at higher frequencies while moving the ink through the printhead. The RC1536 is available in two models—M and L—and is considered one of the top printheads in ceramics, high ink deposition, and inline white printing, according to the company.
Xaar’s 5601 printhead has been in development for seven years. It uses Xaar Thin Film Piezo Silicon MEMS technology, which provides a high resolution with over 5,600 nozzles capable of jetting up to eight liters of fluid per hour. AcuDrp Technology controls greyscale drop ejection, yielding perfect image quality. TF Technology maximizes production uptime, print quality, and lifetime. Crafted with a Z profile, multiple printheads fit closely together, which offers compact print zones, accurate drop placement, and reduced costs in association with accurate media control and positioning. The Xaar 5601 is optimized for aqueous ink and is ideal for textiles, laminates, commercial printing, and packaging applications.
Printheads in Action
The perfect marriage of a printhead and a wide format printer/ink leads the way for endless uses when it comes to digital printing. Today’s print hardware is equipped with robust printheads that allow for almost anything to be digitally printed on. In addition, the printheads are designed to offer high productivity with a prolonged life.
Apr2018, Industrial Print Magazine