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."
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.
This is not unlike asking, "I want to take the drive electronics off the hard drive and read and write to the platter with the existing head and motors. How do I do that?"
Not only are different print heads from the different manufacturers driven differently, printheads within a single manufacturer are driven differently. There are several ways to eject a drop of ink from the head, and several ways to adjust its trajectory in the air. I suspect the industry has largely moved to one or two methods that are similar, and I also suspect that the driving electronics are very similar, at least from a high level view.
What you'll find, however, is that each printer has a specific ink, a specific nozzle, and a specific distance to the media, such that you will probably find as many similarities as you will find differences between two printers.
Why is this important? This is the reason why very few people have done this sort of endeavor.
However, you are probably looking for a low resolution (100-200 dpi), and are only looking at doing one of these things. so go get a cheap printer and an oscilliscope and read the voltages present at the head when it's printing. You will likely need to duplicate the voltage and pulse length, but you can probably ignore the pulse shape and perhaps even the slew rate since you are going to have a lower resolution and you won't care if the thing breaks down in 1000 hours rather than 10000 hours.
If you trace the circuitry, you might find they use separate chips to drive the head, and will produce the right logic levels given a simple digital command - some judicious signal hunting will tell you all you need (or some good data sheets). This might give you an edge, since you wouldn't have to create your own drivers.
If you want to try and use more of the printer, then you can hack the sensor that tells it how far along the track it's gone. Just expand it (digitally or by building a new sensor) and then hook its stepper outputs to a higher current drive and have that drive the real stepper. Just magnify everything. You'll have to deal with a low ink output, though, so there's always some gotcha.
Then you get to enjoy trying to keep the print head exactly x millimeters from the paper across the 60" width. Usually this is done with a long, large, rigid drum os some sort and some tensioning drums.
You didn't give us much info though, so I can only answer the question you have, not solve the problem you have. What about your project makes a pen plotter type system inapropiate?
-Adam
An inkjet printer precisely moves a print head back and forth above the paper path. That's the part of the printer you want to keep. Another part of the printer precisely moves the paper, you want to replace that part of the printer.
Find the wires that lead to the stepper or servo that precisely moves the paper. Replace that with a larger motor that can precisely move what's left of your printer. You will probably need to boost the power. You can use the old stepper signals to drive opto isolators that drive some big MOSfets. (or a simpler circuit of your choice, that just happens to be how I used my Lego Mindstorms to control some much larger motors. Google for "y3md".)
If you can't dissassemble your printer so that the printhead can scan across your workpiece, start over with another printer. (that's why it is good that the printers are so cheap.)
The next challenge is getting each pass lined up with the previous pass. This is very hard. Don't even try. Instead aim to overlap each pass. At the start of each pass, precisely measure the overlap, and generate an appropriate image to render. It is far easier to measure something than to move something.
I looked into this a while back. Unless you have the ability to make tiny springs and gears, mold your own plastic and metal, you're not going to be able to make one of these things for less than you can buy one (or three!).
The specs for the off-the-shelf printheads are unavailable. And the interface is designed to be difficult to reverse engineer to prevent 3rd party printheads from becoming available.
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.
You aren't.
Take a look at Output magazine. It's the trade rag for the digital print finishing industry.
Ink jet printers have been used for everything from cake decoration (photo quality image made of frosting. Yum, Yum.), to etching brass and wood.
You can probably buy what you're looking for without having to be creative or inventive at all. Though that might take the fun out of it.