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Printheads Grow Up

The Technical Aspect of Print

By Gretchen A. Peck

There’s no more a dynamic segment of the global print market than large format graphics. The players are ever changing, with industry veterans joined by other types of print service providers (PSPs) now offering big inkjet work. And there are those individuals who seemingly happened upon this as business, through personal passions like photography and fine art reproduction.

 

“Inkjet is relatively new in the wide format graphics market,” according to Ed Chrusciel, marketing director, Fujifilm Dimatix, Inc. “We consider it to be a mature market because the growth rate has somewhat slowed down a little bit.”

 

The evolution of printheads for inkjet printing has a lot of do with this maturity. In a short span of time, they’ve been adapted for better resolution, varying inks, and engine architecture.

 

“Printheads have gone through several generations over the past decade, advances that expanded the number of nozzles supported by printheads, expedited firing rates, and enabled them to fire smaller droplet sizes,” notes Eric Zimmerman, product manager, Roland DGA Corporation.

 

Eviatar Halevi, director of technology, large format, Scitex Industrial Printing, Hewlett-Packard (HP), says that the most notable printhead developments include higher drop-placement accuracy, greater flux per dollar, smaller drops, and grayscale.

 

Resolution also increases exponentially as viewing distances for large format graphics decrease.

 

“The people making decisions about purchasing print jobs are doing so on the desktop. Meaning color is viewed at arm’s length viewing distance, even if it’s for a billboard. Resolution plays a critical role, as far as the printhead design,” explains Chrusciel.

 

Influencing Development

New inks, substrates, even print engine design factor into how printhead creators turn out new technologies.

 

“From our point of view, the ability to develop a printhead technology capable of handling multiple ink channels and chemical types—while providing a higher number of nozzles for improved print speeds—is essential,” notes Mark Radogna, group manager, product development, Epson.

 

Epson’s latest MicroPiezo TFP printhead technology was introduced with its SureColor S-Series of solvent-based printers. Several breakthroughs are addressed including extreme dot placement for improved overall print quality, more than double the nozzle count for significant print speeds over the company’s previous generation, and the ability to handle both white and metallic ink.

 

Xaar is a globally recognized manufacturer of acoustic-wave piezoelectric drop on demand printheads.

 

What distinguishes this particular type of printhead? Mark Alexander, director of marketing, Xaar, explains, “We vibrate the walls of our actuators and create an acoustic wave that pushes the drops out through the nozzles. This creates industrial-strength printheads that last for years because we have no mechanical stress.”

 

Alexander and his colleague Mike Seal, product manager, Xaar, agree there has been considerable R&D on printhead technology in recent years. “Clearly, there’s a steady progression of speeds and resolution,” explains Alexander.

 

Reflecting on recent Xaar-specific examples, Seal remarks on TF Technology introduced with the Xaar 1001 product range. “What happens with this architecture is the actuator is such that the ink is re-circulated right past the back of the nozzle, so the channel and the nozzle are continuously re-primed with fresh, conditioned ink,” he shares.

 

“One advantage of the recirculating systems is the fact that highly pigmented fluids are maintained in suspension far easier, so you can run high viscosity and high density—like with white ink, metallic, or varnish, and ceramic ink, for which we’ve been particularly successful,” remarks Seal.

 

Potential Printhead Pitfalls

With advancements in printheads, the delicate nature of these products grows. Care and consideration must go into the maintenance of the entire system.

 

The printhead is just a single component of the ink delivery system, according to Zimmerman. “The way you drive and move the printhead is just as important as the printhead itself. So, in addition to the speed and durability of the actual printhead, you should examine the entire print engine, including carriage design and chassis construction, as well as the materials used for each component.”

 

Numerous variables determine lifespan, making it difficult to predict. “Life is rated in the number of shots the printhead fires over its lifespan, which is typically in the range of several billion. Maintenance of the printer has a lot to do with how long components last, including the printhead,” advises Zimmerman.

 

Xaar warrantees its printheads for a year, according to Alexander, who confides that the expectation for lifespan is more like two years, possibly longer.

 

“Every environment is different. Maintenance, attention to detail, cleanliness—all of those things vary. The type and quality of inks used, filters, and even the cloths matter. There are a whole bunch of factors, so it’s hard to put some exact figures on that. But we say with confidence that we make industrial-strength printheads. They are not intended to be disposable,” asserts Alexander.

 

“Printheads don’t have any failure mechanisms built into them,” notes Chrusciel. “There are no fatigue factors. But printheads do fail.” Fujifilm identified multiple reasons for failures, including head crashes, which is when media comes in contact with the printhead. This occurs when the material is moving too fast and rises up and buckles.

 

Printheads work best when they’re used in the way in which they’ve been designed to work, asserts Chrusciel.

 

“Compatibility is a very big issue,” he confides. “If you talk to a guy who has a printer, and you explain to him that he should really use the manufacturer’s recommended ink, he may say, ‘Nah, they’re just trying to gouge me. I’m going with aftermarket inks.’”

 

“But the point is that from the manufacturer’s standpoint, they rigorously tested those inks for jetability and sustainability over periods of time,” continues Chrusciel. “They even do things like soap tests, where pieces of the printhead sit in ink for a long time—50 or 60 days straight—to see if any kind of damage occurs, like pitting or similar things of that nature.”

 

This also holds true in regards to using a printhead designed to work with specific ink chemistry. “For example, if the customer is printing using dye-sublimation inks, thermal printhead technology cannot be used. A piezo-based printhead technology is superior for this ink chemistry,” says Radogna.

 

He goes on to explain that printhead life is maximized when used with the specific ink chemistry and delivery method it is developed for. Many PSPs purchase a printer and then use it for other applications and ink types, this lowers printhead life and reliability.

 

New to You

Though the large format market may be considered mature and stable, print engine makers and their printhead partners don’t intend to rest on any laurels.

 

Xaar plans to launch its new printhead—the Xaar 501 GS10—later this year, which is targeted directly to large format graphic systems. The company will first announce it privately to OEMs, allowing them to participate in further development, rigorous testing, and a more formal introduction to the marketplace.

 

“The StarFire SG-1024/M-C is our newest product and it offers many unique features. Continuous ink circulation is one and it was designed originally for a particular application—ceramic tiles. It’s an oil-based ink with glass frit in it, which is abrasive and heavy—and had the tendency to settle out. Our recirculation allows it to use a lot of industrial fluids,” remarks Chrusciel.

 

The Fujifilm StarFire SG-1024/M-C was first introduced for ceramic. Then the StarFire SG-1024/M-A for textile applications debuted. The C denotes it only used for oil-based inks, while the A jets solvent, UV-curable, and aqueous ink, so it’s targeted to a much broader segment.

 

Printhead creators are challenged by their print engine manufacturing partners, as is the case at HP. Halevi confides, “I think that the time for single-pass printheads has come. Drop weights and frequencies are about right, but a key missing element is the ability to pack many nozzles in a single chip in a very cost-effective way.”

 

“For a single-pass printhead to be effective one needs to reach enough uniformity across the printhead, to control every single nozzle individually and to build enough redundancy inside. To deliver this at high resolutions, vendors need to find a way to bring the cost of a single nozzle down significantly,” he explains.

 

Start Your Engines

Seal suggests that PSPs think of their print devices as automobiles. “It’s similar to owning a car,” he expounds. “The engine is the printhead. Its longevity and dependability rely on the ink—the oil or fuel you put into it, how often it is serviced, and whether there is a good service contract.”

 

If your business is considering an investment in a digital inkjet printer, pay close attention to the printheads under the hood. Conduct conversations with the manufacturers.

 

Apr2013, Digital Output

 
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