Kodak demonstrated its Prosper Ultra 520 press at the Hunkeler Innovation Days in end-February, showcasing the next generation of its continuous inkjet technology. Kodak is unique amongst the major single pass inkjet press manufacturers in using continuous inkjet and the company says that this approach allows it to achieve higher ink coverage for more demanding jobs whilst maintaining a high print speed.
Most printheads for high end graphics arts presses work by generating each individual droplet at the required size as and when they are needed. The challenge is to generate enough ink drops to achieve a reasonable print speed, and the only way to go faster is to produce more ink drops.
With a continuous inkjet system, the ink drops are generated in a continuous flow and ejected from the head. Some are allowed to fall to the paper while a secondary system deflects others back to the ink tanks to be re-used. It’s easy to speed up the system – just allow more of the drops to reach the paper up to the maximum capacity of the printhead. This constant flow of ink means that there’s less danger of the individual nozzles becoming blocked so there’s no need for complex ink recirculation. In addition, less humectant is needed in the ink to keep the nozzles wet, which in turn makes it easier to dry the ink on the media.
The UltraStream print engine is an evolution of the Stream technology that Kodak debuted back in 2008 with its Prosper presses. The Prosper 7000 turbo still remains one of the fastest inkjet presses around. Randy Vandagriff, a vice president at Kodak and senior vice president for its Print division, explains how the system works, “With Stream we are generating the drops at 400 kHz, with 2.5 picolitre droplets at 450,000 droplets per second. When we print we change the frequency of the jetting to 150 kHz which forces some of the smaller drops to merge to give a bigger drop. There is an air curtain that blows the little drops off course and lets the bigger drops through because they are heavier.” This leads to a 9.6 picoliter drop size, with 600 x 900 dpi resolution that reaches the substrate.
For UltraStream, Kodak has combined two different technologies: the Stream continuous inkjet jetting plus a separate electrostatic technology that allows for much smaller droplets. Vandagriff says, “They are both very proven technologies but this is the first time we have brought the two together.”
The UltraStream system uses a pressurised manifold that creates around 400,000 drops per second. Each of these drops is 3.75 picoliters delivering 600 x 1800 dpi resolution. Vandagriff continues, “There is a heater on the nozzle plate around each nozzle. We heat it to 5°C and it causes the drop to break off. The heater is oscillating on and off at 400 kHz.”
“Then there is an electrode with a negative charge. We can time it so that as the drop breaks off, if the charge is on it attracts the drop away to be deflected. The charge is always switching on or off. If the charge is off then the drop goes to the paper and becomes the print drop. So it’s like a hose. We are spraying the ink out of the nozzle with 50 psi pressure at the manifold.”
He says that the key to the system is the timing between the drops leaving the nozzle and the electrode charging or not charging them.
The ink comes out of the nozzle at a velocity of 20 meters per second, which is much faster than a piezo head, which is typically around 8-10mps. The high velocity allows for good dot placement accuracy because there’s less danger of turbulence around the moving substrate knocking the drops off course, and this ensures higher definition images. This also allows for a longer throw distance of around 8mm between the heads and the media, limiting the risk of dust from the paper surface clogging the nozzles.
The drops themselves are circular and do not stretch out or form satellites as is typically the case with piezo printheads. Vandagriff says, “The drops are the same size. We have very good uniformity. When we break off we get a filament but it merges with the drop because of the velocity. So we get a very round drop.”
Additives in the ink and the primer ensure that the drops form tight dots and do not spread on the surface of the media, which also should lead to sharper images.
Inks and primers
Kodak’s CEO Jim Continenza says, “It’s not about the press but about the ink. We have invested a lot of time and money on ink. We developed all new ink for the 520 and it was costly because we had to do it three or four times to get it right. It hasn’t been easy. 40 billion drops per second is not easy.”
The ink is Kodak’s nano particulate aqueous pigment ink, available in CMYK only. This is a water-based pigment ink, with the pigment particles micro-milled down to less than 50 microns. Vandagriff says that Kodak owns a proprietary milling technique that allows it to produce much smaller pigment particles than other ink manufacturers. This makes the ink easier to jet but also leads to a thinner layer ink on the substrate. Vandagriff says that this allows more light to penetrate through the ink and to reflect back from the substrate surface without scattering and that this allows more vibrant colours even though there’s less actual pigment being laid down.
Alongside the ink, Kodak has developed a series of primers, or optimisers, with different ones designed to work with different types of substrate. Vandagriff says that Kodak has developed a low cost optimiser that allows the Ultra 520 to take on both uncoated papers and matte and glossy coated offset stocks. But the same writing system can also be used for packaging applications simply by using a different optimizer.
Indeed, Kodak has partnered with Uteco, which uses the UltraStream inkjet system for its Sapphire W press to print to flexible films. But this is not an exclusive arrangement and Vandagriff wouldn’t rule out Kodak developing its own presses in the future for other markets such as labels and packaging. And it’s worth remembering that Kodak did originally demonstrate a prototype label press using UltraStream printheads at the Drupa 2016 show.
As well as the optimizer, there’s also an optional post-coating to add gloss and to protect the inks from scuffing. Kodak used a pretreated paper roll on its stand at HID2023. This is because the normal configuration is a pre-coater from ContiWeb but Hunkeler wasn’t keen on having this running on the stand.
The Prosper Ultra 520
So, that’s the technology; now lets look at the press itself. The Prosper Ultra 520 is a single pass inkjet press that’s designed to print to standard offset papers for commercial print applications such as books, magazines and direct mail. It’s a roll-fed press with a 520mm print width and can print a a maximum page length of 3.8m.
Inside the Ultra 520 press
The Ultra 520 runs at 152mpm, which equates to 2020 A4 images per minute printed two-up duplex or 12,950 B2 sheets per hour printed four over four. It can run at the same speed with only the black heads active, which reduces the cost for monochrome applications. It can handle up to 60 million pages per month. It can run standard offset papers, both coated and uncoated, with an optional inline precoater as well as newsprint and inkjet treated stocks.
The UltraStream printheads can each print a 104mm wide swathe. The 520 has five heads per color. Kodak says that in theory it can build printbars up to 249cm long but in practice this is currently limited by the DFE, which for the time being can only handle print widths up to 1.2m. Resolution is 600 x 1800 dpi, which Kodak says is equivalent to 200 lpi. The press can print 90% of the version 5 Pantone PMS colours within 3 dE.
There are two versions, the C520 that was shown in Luzern plus a P520. The main difference between the two is the number of drying units. The drying is intelligent near infra red from Adphos. The C520 has been designed for high ink coverage applications on papers from 42 to 270gsm and has four drying units. The P520 is designed for medium to low ink coverage applications, on papers from 45 to 160gsm, and only has two drying units. The P520 can handle heavier stocks than 160gsm but might see a reduction in speed. It’s possible to upgrade from a P520 to a C520.
The typical configuration might include an unwinder, pre-coater, press, post-coater, performation/ punch unit, a rewinder and then a sheeter and book finishing unit. The press was shown with a Hunkeler UW8 unwinder and RW8 rewinder along with an optional Hunkeler WI8 web inspection system. Phil Walsh, VP of digital sales, says: “We have an open architecture and can have auto splicers at the front and can precoat, with a post cutter and sheeter for finishing.”
The press comes with a Kodak 900 Print Manager DFE, which can handle PDF, PDF/VT and AFP files. This is based around what is supposedly the latest Adobe APPE 5 RIP though Vandagriff did seem surprised when I pointed out that Adobe released APPE 6 last year. Nonetheless, this is backed up by Kodak’s proven Prinergy workflow and the Prinergy On-Demand Business Solutions, which also includes an MIS and e-commerce coupled to the Microsoft Azure cloud.
So far Kodak has sold one Ultra 520 press, which Vandagriff characterises as an early adopter rather than a classic beta site, saying, “We are working on terms with them.”
The press is available to order now but Vandagriff notes, “We want to roll this out in a more controlled manner. We are really focusing on who the right customers are. We want to go with a customer that has the kind of work that we want on this press. So our customer will take out a Komori offset press and two toner machines and migrate everything over to our press.”
I can’t publish who makes the toner machines involved at this site, but I can say that these were not light production machines but high end digital presses. Some of the journalists that I spoke to in Luzern were sceptical as to whether or not offset users would want to switch to inkjet. But if one inkjet press can replace an offset machine, a platesetter and two digital printers, with all the associated maintenance costs and workflow complexity then I suspect that more offset printing companies will be reaching for their calculators and looking at the numbers.
Vandagriff says that anything that is being done today on an offset press or digital machine can be done on an Ultra 520, adding, “We can do packaging. So we can hit all types of markets including home decor as we move broader and broader with our technology.” He continued, “We are looking to move large volume of offset work to our inkjet system as well. And we want to go from high quality and high speed and anything in between.”
It will certainly be interesting to see both what kind of print companies buy the Ultra 520, and what direction Kodak takes the UltraStream technology in. You can find further information on UltraStream and the Ultra 520 from kodak.com.
Published by permission from www.nessancleary.co.uk