Xerox has this week shown something closer to a production version of the high-speed ink jet system they showed at IPEX last year. The unfortunately named Xerox Production Inkjet System (PIS) is claimed to be the first waterless high-speed ink jet press, although some might say that Miyakoshi has shown high-speed UV curable ink systems before and they are waterless.
Xerox is using an iteration of their phase change inks, and points out that by not having water in the system they can avoid paper cockle and drying problems. The phase change inks solidify on contact with the paper substrate and sit on the surface ‘just like offset inks and toner’. Our tracking of patents has shown that to achieve acceptable drop spread on the substrate, it must be pre-heated. The paper then passes over heated shoes opposite the printheads. With phase change inks the ink supply tanks, connecting pipes and printheads all have to be heated.
The printheads are arranged in a large 2D array and Xerox says they are automatically aligned. Certainly keeping them all in register with the thermal cycling within the machine must have been an engineering issue. The heads are operator replaceable and involve 2 screws and 3 connectors, taking 5 minutes.
The print speed is a very impressive 152 metres/minute, or 2.53 m/sec. At the quoted ‘up to 600 dpi’ this would lead to a nozzle frequency of 60.8 kHz. This may be achievable but my guess is the highest speed is at a lower resolution than 600 dpi. Incidentally the patents talk of 3.75 m/sec.
Something else the patents talk about is printing packaging materials. The problem then is finishing, with the substrate, creasers and cutters having to be heated to avoid picking up ink.
The system shown will print on to low-cost offset papers without bonding agents or pre-coats, says Xerox. However noticeably absent from the presentations I’ve seen was mention of coated papers. As phase change inks rely, like toners, on mechanical keying to the substrate, coated papers are likely to be more of a challenge.
And yes, I was too cheap to fly to Lucerne, Switzerland to see the machine at the Hunkeler Innovation Days 2011 show in Lucerne, Switzerland – I’ve just attended the virtual event on-line.
You might read into this post that I’m not a great fan of phase change inks and you’d be right. I’d like to love the technology, I guess I’ve just had my fingers burnt a few times handling the printheads!