By Melissa Donovan
Printhead manufacturers are pulled in multiple directions thanks to new trends in digital printing. Far from remaining stagnant, the newest advancements to printheads include higher velocity drops to compensate for printing to untraditional materials, nozzle guards that protect the printhead from loose fibers of fabric, and flexibility to print with numerous types of ink sets depending on each user’s requirements.
Above: Epson’s PrecisionCore printhead technology is suited for a range of heat-sensitive ink technologies.
Demand in wide format digital printing influences printhead design. Main themes are speed, quality, cost, and versatility.
According to Timothy N. Rosario, senior product manager, Fujifilm Inkjet Solutions, wide format digital printing is still looking to push the boundaries on productivity, image quality, and price. Concurrently, printheads are expected to have these same qualities, all with a lower cost per nozzle.
Delivering higher volumes of ink and improving print quality is achieved by increasing printhead jetting frequencies and smaller ink drop volumes, shares John Harman, director sales and strategy, Ricoh Printing Systems America, Inc.
“Wide format print requirements continue to increase around speed, quality, and cost. In response, single pass printheads will focus on increased nozzles, more ink compatibility, smaller drop sizes, higher firing frequency, and longer life capabilities—all impacting overall print performance,” notes Kevin Shimamoto, CMO, Memjet.
Versatility is prevalent. “As printers and applications diversify, many printheads are designed as scalable systems that work with different types of ink technology,” says Reed Hecht, senior product manager, Epson.
Scalability is a theme behind Epson’s PrecisionCore printhead technology, which is found in the company’s consumer-level desktop printers to large industrial presses. Another focus is multiple ink sets, with the printheads able to jet aqueous, solvent, UV, and dye-sublimation ink. “The PrecisionCore printhead technology doesn’t use heat to eject the ink and is therefore suited for use with a range of heat-sensitive ink technologies,” adds Hecht.
A major trend is digitally printing to textiles. “With the increase of printing onto the fabric, newly launched and upcoming printheads must be capable of jetting aqueous inks required for textile printing,” explains Jason Remnant, senior product manager, Xaar plc.
In response, Xaar recently launched the Xaar 5601 printhead. Designed to print aqueous inks onto textiles, it also is capable of jetting two colors within one printhead, has over 5,600 nozzles in each printhead, and a compact print zone thanks to the Z profile of the printhead.
Unique and Different
Untraditional materials from pre-manufactured goods to raw wood are printed to using digital flatbeds. Printheads must adapt to work well with these substrates, overcoming challenges like ink jetting from a greater distance.
According to Shimamoto, there are several design aspects within the printhead configuration that allow greater capability to print on wider, thicker, and less uniform materials such as high drop velocity, ink recirculation, and more automated maintenance.
“Image quality is still expected to be quite good, however these materials are often textured and uneven, requiring standoffs higher than normally expected with paper and other wide format graphics media. That translates to printheads needing to print from a safe distance. Requirements for high velocity drops with excellent straightness that can traverse these wide gaps between the printhead and the lowest point of the surface become critical,” explains Rosario.
Seiko Instruments U.S.A., Inc. recently announced the RC1536 printhead, part of the RC Series that offers improved precision jetting for printing on undulating structures like ceramic tiles. Main features of the printhead include an ink circulation structure, isolated channel structure, 108 millimeter print width, and 1,536 nozzles. The RC1536 is compatible with oil, UV, solvent, and aqueous ink.
Remnant says challenges like more edges to negotiate—for example on boards or door panels—increases the potential of damaged printheads. In addition, different substrates vary in their printing requirements in terms of how much ink is needed and printing mode.
To remedy issues like the amount of ink required, Xaar outfits its printheads with TF Technology. Ink recirculation ensures the printhead adapts to different substrates requiring different inks. This means that the printhead can reliably jet heavily pigmented inks like white.
Automated maintenance is a necessity. With increased particulate contamination—for example sawdust from wood—printhead design must become more robust and offer mechanisms for automatically cleaning printheads regularly, says Harman.
Fabric is increasingly directly printed to using today’s digital printing technologies. As printheads also adapt to work with these substrates, they must overcome challenges.
“Within printhead design, issues surrounding drop sizes, firing frequencies, drop velocities, and ink circulation among others need to be addressed in conjunction with the proper ink and fabric compatibility to recognize the wide range of substrates and applications within the textile segment,” suggests Shimamoto.
Textile printing challenges include loose fibers shedding from the fabric. To combat this, manufacturers like Xaar work on features such as nozzle guards. The nozzle guard on the Xaar 5601 printhead recesses the nozzle plate by approximately 0.2 millimeters. “This means that the nozzles and surrounding nozzle plate area are further away from the printing substrate and the risk of damage to the nozzle plate from loose fibers is reduced,” shares Remnant.
Garment and décor manufacturers expect a certain level of consistency lot to lot. Printheads must be able to offer this when it comes to printing directly on textiles. “When printing with fabric the ability to print a job, and then duplicate that job with the same quality and color accuracy the next day or even a year later is important,” explains Hecht. Epson PrecisionCore printheads offer the ability to duplicate jobs with the same quality and consistency as the prior job.
Another area of concern, according to Rosario, is ink latitude. Textiles can be printed with a variety of ink from acid, dye, and pigment to reactive. Printheads need to allow customers the flexibility to use the inks that meet their demanding needs.
Aqueous inks are commonly used in digitally printed textiles, but are more prone to drying at the printhead nozzle plate. Certain steps need to be taken to address these drying issues. “Flow through or recirculating technology both through the ink manifold and behind the nozzle plates ensures that each individual nozzle meniscus remains active and therefore less prone to drying. Modifying the printhead waveform also facilitates maintaining an active nozzle meniscus,” recommends Harman.
Ricoh’s MH5421/5441 printhead is designed for use with aqueous ink. With 1,280 nozzles configured in four by 150 dpi rows it achieves 600 dpi resolution printing. Made of stainless steel, the printheads offer excellent anti-corrosion properties.
Expectations for the Future
Life of the printhead, image quality, and productivity are some of the main features considered for a printhead used in wide format printing devices.
Rosario points out that printhead life is a given these days. And beyond this expectation, he feels that Fujifilm’s Si-MEMs based products address several future market needs like optimizing speed, coverage, and total output. In addition, the company strives to develop cost-effective methods for meeting unique requirements of varied application and market segments.
“A robust printhead with a reasonable lifetime is one expectation. Most printers on the market now meet or exceed the print quality requirements of wide format print applications. What is important now is for OEMs to produce machines that offer a lower total cost of ownership (TCO) without compromising on print quality or productivity,” suggests Remnant.
For wide format in particular, Shimamoto believes printheads need to expand in width to minimize the number to stitch, offer smaller drop sizes below two picoliters to optimize image quality, work with pigment ink, feature high firing frequency for fast print speeds, and extend life to minimize interventions and TCO.
Width expansion is something Memjet focuses on with its DuraLink printhead, which measures at 8.77 inches in width with 70,400 nozzles and five times nozzle redundancy.
“Continuous improvements in fluid handling both within the printhead, at the nozzle plate, and to the substrate are also expected as wide format digital printing expands to encompass untraditional materials that require exotic fluids and increased jetting distances due to increased surface thickness tolerances,” adds Harman.
Epson’s mantra is quality is a critical element to any print technology. “When a customer is matched with a printer that delivers the intended quality and production, they are given a solution that enables them to differentiate their offerings,” explains Hecht.
Paired with a commitment to quality, Hecht says many Epson customers look for automated maintenance of their printheads. This reduces the amount of labor, which when combined with the durable printheads, saves users time and money.
Today’s printheads are at the forefront of the push to move digital printing into new verticals. Without recent advancements, the possibilities of printing to textiles, wood, and tile would be limited. Speed, quality, cost, and versatility are critical factors that play a role in future developments.
Mar2019, Digital Output