Editor’s Note: This text was presented in its original form as a panel discussion at the 2013 SGIA Expo (Orlando, October 23–25). The information gathered is not inclusive of all available printhead technologies, and focuses solely on the characteristics of that company’s equipment represented by each speaker. The text that follows is a mix of verbatim quotes (italicized) and editorial summary where verbatim transcription was not possible.

At the 2013 SGIA Expo, some of the leading inkjet printhead manufacturers discussed the state of their technology in a well-attended panel session. This informative panel included representatives of Fujif ilm Dimatix, Epson, Konica Minolta, Seiko Instruments (SII-Printek) and Xaar as well as a user's perspective from EFI-Vutek. The topic was inkjet heads for graphics applications, and how future technology advancements may unlock new opportunities in graphics production and beyond. Piezoelectric drop-on-demand

inkjet printheads are truly one of the most important components to wide-format and other inkjet-based imaging devices, and recent developments in inkjet head design and manufacture have strongly affected print speed, quality, the ability to produce unique effects and more.

Some of the presentations were quite technical, so first a quick primer on printhead technology: The world of inkjet can be split into Continuous Inkjet ('CIJ') and Drop on Demand ('DOD'). CIJ, which is used for date-coding food products etc. was not discussed here. The DOD arena breaks Into Thermal Inkjet ('TIJ') and Piezoelectric Inkjet ('PIJ'). TIJ is widely used in the graphic arts market — notably by HP and Canon — but the manufacturers at this session were all makers of PIJ printheads. PIJ heads work by applying voltage pulses to a piezoelectric material, which deforms in response and so ejects ink droplets from a chamber via a carefully engineered nozzle. Each printhead has hundreds or thousands of such chambers and nozzles.

Chris Lynn, CEO, Hillam Technology Partners

diversification

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The main areas of development and debate in printheads today are in the use of silicon MEMS (Micro-Electro-Mechanical Systems) technology in their manufacture, and the benefits and drawbacks of 'shared wall' technology as opposed to 'isolated channel' designs, 'greyscale' or variable drop sizes, and recirculating ink paths. These are explored in the comments below.

John Lapp (Fujifilm Dimatix)Printheads have been used in digital printing, coding and marking for years, before wide-format graphics became a huge market 10 years ago. It is still a huge market. But ceramics is growing; commercial printing applications are growing, along with 3D prototyping, functional applications, deposition applications in printed electronics, bio-science applications, where printheads are used as a micro-pump or a precision dispensing tool in jetting fluids other than ink. A lot of inks have been developed for printed electronics, silver inks, copper inks, gold inks, nickel inks all conductive, so you can use an additive process rather than a subtractive process.

In terms of the technology, we don’t use shared wall, we use shear mode; it enables high-frequency operation. With the new Samba head, we’re jetting upwards of 150 kilohertz (kHz). Our industrial heads are 50–60 kHz. There are really no wear mechanisms in a printhead; it’s really the environmental conditions and maintenance that determine the life of a printhead. If it’s well maintained, it will last a long time. If it’s abused, it won’t last very long. We get excellent uniformity out of the head in terms of drop volume, jet velocity, jet straightness and wide temperature range. Some of the heads run up to 125 degrees Celsius, depending on the type of ink used. Drop sizes range 10 to 150 picoliters in a wide range of fluids — aqueous, solvent, UV-curables, phase-change or functional inks like nano-silvers or bioscience fluids.

Many factors affect print quality: Drop velocity, drop volume, jet straightness and jet-to-jet uniformity. A printhead with a high jetting velocity allows for high stand-off distance, so depending on your application, whether you’ve got a big flatbed moving heads over a large area, a higher stand-off is going to limit the amount of head strikes you may get. It is important to get uniform drop volume out of every jet. If you have inconsistent drop sizes or a wide tolerance, you’re going to see banding in your imaging. Jet straightness is also very critical; again it’s going to cause banding or fuzzy images. Jet-to-jet uniformity means all three are consistent. Two out of three is not good enough; you need three out of three.

Likewise, a couple of factors affect drop

placement. First is the manufacturing tolerance of the printhead, which is shown with the nozzle placement error. There is a tolerance in terms of manufacturing nozzle plates. But then there’s the jetting error and again, the manufacturing process of the nozzle can affect that: Scratches on a nozzle plate; dust on a nozzle plate; cured ink building up around the nozzle plate can start to pull the jet over.

In terms of print quality, Versa-drop is what we call our greyscale technology, where you can have very small drops for high-resolution, closer viewing. You can have large drops for long-distance viewing or you can use greyscale, variable drops to achieve text or flesh-tones.

Masao Tachibana & 'Waka' Wakabayashi (Seiko Instruments, Inc — Printek)SII-Printek's presentation began with a description of their 'isolated channel' architecture, highlighting its advantages over the 'shared wall' technology used in their earlier printheads*, which include higher frequency operation, higher jetting velocity, and no corrosion with aqueous or conductive inks. The speakers also described their latest development — the use of a recirculating ink flow design**. The benefits are self-priming, automatic recovery from jet-outs, and reduced sedimentation when handling inks with high solids content.

The presentation then analyzed the question: "Is a small drop-size always better for image quality?" The argument made was that the placement accuracy of the smallest drops is likely to be affected by airflow and electrostatic effects; and that productivity — measured in drop volume per second — is helped by having larger drop sizes. There is always a trade-off, came the conclusion, and SII offers a range of printheads to meet both single-pass and scanning application needs, with sub-drop sizes from five to 20 picoliters, and full greyscale drops up to 200 picoliters.

*Shared wall architecture is also used by all Xaar and some Konica Minolta heads.

**This is similar to that incorporated in Xaar's 1001 series, and Dimatix' Samba and Starfire heads.

Daisuke Ishibashi (Konica Minolta)The KM presentation described the company's full range of printheads, and in particular highlighted the 1024 and 1024i series. Each model in both series has 1024 nozzles, but the older 1024 series uses two rows of 180dpi actuators operating in 'shared wall' or 'three-cycle' mode, whereas the

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newer 1024i series uses four rows of 90dpi actuators to achieve the same nozzle density, but with significantly higher frequencies of operation. Remarkably, all the heads have an identical (and narrow) footprint: 106 by 18 millimeters. Each family comes in small, medium and large-drop versions, and the similarity of mechanical mounting, electrical connection and ink connection provides great flexibility for customers.

The latest printhead model is the 1800i features 600dpi, 84 kHz operation with a 3.5 picoliter drop size. It is promised "very soon."

Juan Calderon (Xaar)What does the customer want from the printhead? We classify this in five categories: Print quality, productivity, reliability, ease of integration, and maintenance and service costs.

Print Quality and Productivity: Xaar is working to come up with a new generation of printheads that will have a smaller drop size, wider print width and will print at higher frequencies.

Reliability: Xaar offers through-flow technology in the Xaar 1001 head. It has been very successful in single-pass applications for ceramic tile printing and label printing, and we’re now adapting it to the multi-pass industry.

Ease of integration: Everybody wants to be able to build a printer easier and faster — and when you do build a printer, you want to be able to replace the heads a little bit faster, and go to market. All of our heads will now have a Luer lock fitting to secure the ink connection, and the electrical connections will be coated to protect them from mechanical and electrical damage, ink spills and so forth. These are some things we are hearing from the public, from the end-user, to improve our product.

Maintenance and service costs: We have a new generation coming up with smart electronics. The smart functionality will allow for feedback directly from the printhead; the ability to control temperatures and voltages; to help diagnose and prevent damage to the head.

Mark Radogna (Epson)I represent roughly 5,000 of some of Japan’s best mechanical and chemical engineers. Epson is located in Hiroka, Japan. We recently just announced a brand new printhead technology that is going to affect every future Epson printer going forward.

We just introduced a brand new printer. It’s dedicated to do nothing but T-shirt printing. That printer would not exist if we had not developed a brand new printhead, PrecisionCore. This is a completely new

generation printhead developed all in-house. It is completely piezo-based and unique to Epson.

There are four major benefits of Epson’s new PrecisionCore print head technology. The first: It’s based on what we call a print chip core. It actually is no longer just a printhead with a giant array, but a little itty-bitty chip core. It has the ability to produce a dot that is so sharp and clear and accurate that it goes beyond anything that we have ever done today.

We have also been able to utilize more advanced forms of piezo material or crystal. And because we are a founder in that technology, we have been using more advanced forms of chemistry to create that piezo crystal. The result is an extremely durable printhead.

A third major benefit of this new head, it has outstanding ink flexibility. We can print with virtually any ink. We can use a normal water-based pigment; we can use a hard solvent, a mild solvent; we can use new ink that makes a T-shirt. There are a lot of ways we can run fluid through this new print chip.

And finally, it’s scalable. Epson makes a single little chip I can put together to build any array I want, in any color space I want, for any application I want. It’s brand new. This is completely new technology.

So here we have an example of how we’ve taken a brand new idea around piezo, dramatically changed the technology, creating this new PrecisionCore chip. We created a head out of it for a particular application like T-shirt printing, and even within that model, we were able to take advantage of the uniqueness of this new head and actually break it and make two different SKUs out of it.

John Duffield (EFI VUTEk)What do printhead manufacturers need in the next generation of printheads? I work for EFI, formerly VUTEk, so this is a little biased toward our products. Our products include superwide-format digital printers (under the VUTEk name), wide-format printers (EFI wide format) and I’m going to go into the requirements we have for our printers in the future. We acquired (Spanish tile-printer company) Cretaprint, and we heard about the need for new ceramic technology. So I’ ll list some of the requirements and specs that we need on a printhead for the ceramic industry. Moving on to Jetrion, our label printers, their requirements are a little bit different than the wide-format and ceramics printers. Finally I’ ll talk about a few of the slight differences in the textile printing business from the VUTEk perspective as well.

Knowing what technology we have now in the business and what precision and accuracy we can achieve, I’m looking forward to what

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I need for next generation printers, what additional accuracy, what I want these guys to do better so it makes our print quality and speeds better for the future, because we are looking to double our quality and speed every two years in the superwide-format business. I’m looking for angular deviations, probably around 0.4 degrees, or seven milliradions, in all gray levels. I’m looking for plus and minus five percent in velocity variation. I need to be able to achieve that uniformity and velocity.

The other tolerances we’re looking for are, particularly in the x and y plane, to get dot placement accuracy of plus and minus five microns. The z plane doesn’t need to be quite that accurate, maybe plus and minus 10 microns. That would be a pretty tall order, to get those kinds of accuracies with the current technology. I can’t stand any repeating patterns in the deviation or the velocity. By repeating patterns, I mean in the manufacturing process, you might get some waves or frequencies showing up in multiple heads. When you put 48, 96, 144 heads in a print carriage, if those heads have a common trait, that’s going to show up in one mode or the other, and you can’t withstand any of that even to a very small degree. I’m looking for drop velocities in excess of five meters per second. Preferably closer to 10 meters per second, because that will help get rid of some of the drop velocity error, and minimize that for drop placement.

Fluids for super wide, obviously UV curable and probably in the near future some water-based inks for the upper wide industry. Volumes around six to 12 picoliters native, single-pulse, greyscale. We’re currently using four-level greyscale, but a lot of the heads are up to eight capable. Personally, a single row of nozzles is preferable to multiple rows for the superwide-format: It gives us more flexibility, and the chance to place the heads in different kinds of positions. Small packing density, so narrow package size. Very densely packed nozzles make the carriages smaller and lighter, and also make the printing faster, because you don’t have to spread the nozzles out over such a large area. Something that I like to see is some kind of meniscus-pressure feedback. A lot of them already have temperature feedback, but a combination of meniscus-pressure feedback inside the head is going to help get much tighter control on key parameters that affect the print quality, drop velocity and directionality.

Ceramic printers are looking for solvent, oil and water-based inks, which are somewhat different from the UV inks we’re using in the superwide-format. Volume ranges from a minimum of 20 picoliters, up to 50 picoliters native. They fire very viscous, almost-paste ink in a very hot environment. Again, greyscale levels between four and eight, same as the

superwide-format. Native resolutions in excess of 360dpi, mainly because it’s done in a single-pass printer. Recirculating ink delivery for reliable single pass applications is going to be necessary. You don’t get the chance of doing multiple passes and getting any kind of interlacing. Operating temperature range is a little higher than superwide, up to 90 degrees Celsius. High-frequency operation right now operates around 15–20 inches per second. They’re looking to hopefully in the future go up to 70 meters per minute, which is about 45 inches per second scanning rate.

Label printers have some unique requirements. They need very high jet sustainability for long runs without head tending and maintenance. So really, the recirculating heads are a requirement there for nozzle recovery and improved latency. The density or the drop volume across the head and between the heads has to be very uniform. So to that end, if the uniformity is in question, then it needs to be tunable by nozzle, if possible. Similarly for the drop velocities, tuning the volumes and velocities per nozzle would be a huge benefit to the label printers. Mechanical tolerances need to be in the order of the superwide-format, if not a little better than that. Velocities and angular tolerances are very similar to the superwide-format as well. Label printers also need array length itself to be very tight. Even though the nozzle spacing may be somewhat similar, the overall length has to be in the range of plus and minus five microns.

Textile printers are quite similar to superwide-format. The inks and dyes are a little bit different: Solvent, oil and water-based for the textile industry. Drop accuracies and volumes are not as accurate as superwide format, probably closer to what we need for ceramic printing. The textile printers tend to be in some fairly harsh environments, so they need to be able to operate in high temperatures, but they typically have low-temperature inks. Solvent, water-based and oil-based inks don’t like to be heated. So again, easy nozzle recovery, so a scanning, recirculating head would be beneficial.

Question & AnswerAfter the presentations, there was a question & answer session.

What is your ink business model? Do you require people to use specific inks? Do you charge a royalty?

Epson: It depends on the OEM. We have a few friends in Japan that we do OEM our printheads to, and they do take our ink because they require it. But generally speaking, the partners that we have chosen to use our heads, they have the option to use our ink or not.

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Konica Minolta: At KM, we charge an ink royalty.

Xaar: We do require our heads to have approved ink, so that the warranty can take effect. With approved ink, the heads have a one-year warranty. There is some royalty in some of the platforms, especially those that are newer.

Dimatix: Customers are free to use whatever ink they want. However, if they work with one of our ink partners and are using approved ink, they do get a warranty. There are some royalty relationships with those ink partners. We have also some royalty relationships with some customers depending on the pricing model that we have with them.

How long should a printhead last?EFI: If you abuse the printheads, they can last days or weeks. But if you take care of the printheads and maintain them correctly, there is no reason why they shouldn’t last for years. I think we typically see one to two years

as an average lifetime out of our heads for replacement. That’s pretty reasonable.

Do you keep track and analyze that? You have statistics on age of printheads?

EFI: Yes. I can’t pull them off the top of my head, but I think a typical GS printer with 16 heads has an average warranty replacement of two or three heads in the first year. That’s pretty reasonable.

Dimatix: There’s no wear mechanism in the heads, so the piezo doesn’t fatigue; the nozzle plates don’t wear out. It’s really a matter of the fluids you are using. In most typical graphics applications, the fluids are good; they don’t affect the heads. But the key to any application is really maintenance, and cleanliness.

We heard a lot about technology, but what about cost per nozzle or cost in general? What about MEMS and what are you doing to get the cost down?

Dimatix: We don’t really look at cost per nozzle; we look at total cost of ownership. It’s how long a head lasts, what productivity you get out of it. That’s more important than cost of nozzle. Whether it’s two dollars a jet or four dollars a jet, that’s meaningless if it only lasts six months and it’s a slow printer. You want a head to last long and you want to get high productivity out of it. Now in terms of manufacturing costs, yes, we’re always trying to make things better. The silicon MEMS technology we’re using will bring the manufacturing costs down, but in the short term, the costs are quite high because we’ve got a $100 million investment to pay off. You know, the first head was 10 million dollars; the second one was five million. Cost is coming down. So yes, technology drives costs, but it also drives costs improvements with new technology.

Epson: PrecisionCore is a silicon MEMS technology.

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