Slashdot Mirror
Creating Your Own Printer?
hajo asks: "I am in need of a Large (60" plus) printer which can print onto any thickness material for a specific art/robotics project. I loved the earlier Slashdot story where the two students used two motors and an inkjet can for large mural prints; but I need a higher quality end result. I can build a plotter mechanism with two PC controlled stepper motors; But I would like to find out how to use head the parts from a cheap inkjet printer. Where can I find info on the hardware and drivers for such a project. I have a hard time believing that I'm the first who wants to use the ink jet head parts of a printer to do something with them. Any hints, tips and URLs deeply appreciated. I believe this project will make for an interesting read and as thanks for any help I will keep the Slashdot community informed of any results."
We do something kind of similar at work, where we print stuff 24/7 on huge presses running hundreds of feet per minute.
For some of the variable imaging there is row of hacked inkjet cartridges, I think Lexmark with the removable ink-sponge cartridges. They snap off the ink cartridge, and snap in a custom plate with a tube running to a pump and bucket of ink. The electronics are all custom.
I haven't worked directly with them, but even if I did I couldn't tell you any more. I guess you could take it as proof that it's possible...just grab a printer and start playing with a multimeter and power supply. Once you get the right voltage and pin mapping, you're ready to design a solution. If you talk to a professional ink supplier, they may be able to get you an ink formulation that will work in the cartridge...it has to be special. These can work for a long time at a pretty good speed.
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I don't know that I'd try to use commercial print heads at all, because these are precision devices designed with the idea that they have complete control over the print media - level and movement. You're dealing with devices that operate in terms of thousanths of an inch. I just don't think you're gonna get that level of precision from a custom built device and it would be reflected in the output. In particular, I wouldn't think Color would work very well.
It's fairly simple to build something providing the surface you're printing on is flat. You can build a sturdy 2-d frame to hold the printheads across a flat surface, it's the variable height stuff that is a problem. You could rig something up with sensors that could move the print-head up and down, but I wouldn't try it in anything other than unidirectional myself.
For something of this size, I think you'd be better off trying this with something old. Modern ones would kill you in trying to get the head to be just close enough and at just the right location along the surface.
"Why don't you just use a paintbrush?"
There, that should get me a +3 Insightful.
"Derp de derp."
Commercial inkjet carts will be worthless in this application. Very large format prints are typically done at 70 dpi, I've seen billboard proofs as low as 15dpi and they look great (well, when seen from billboard distance).
You want something that can blast out huge dots, not microscopic 1440dpi dots. Plotter mechanisms are difficult to engineer with precision at that size. Most of the largest format printers use a rotating drum like Iris inkjets. You should see Metromedia's custom printers, they use drums the size of railroad boxcars. It is much easier to keep a drum spinning at a constant speed and just run a printhead past it at a fixed speed, than to accurately advance paper in fixed increments through a conventional printer mechanism. Trust me on this, I used to be an Iris technician.