The 3D printer I want to made uses a ink jets to print a chemical onto a building platform. The building platform goes down as a new layer of powder is spread onto it. Then a chemical is sprayed from the print head that will cause powder to bind. If you want more information on these kinds of printers look here
My printer of choice was an old Epson Stylus C63 for these reasons:
1. The ink cartridges only supply ink, they do not have ink jet nozzles themselves
2. I can attach rubber hoses or some other form of tubing that allows me to print another chemical of my choosing
3. The print head nozzles uses a piezoelectric material to produce droplets of ink (lasts much longer than thermal inkjets)
4. Most service manuals for Epson Printers come with a detailed schematic of the main board.
Note: Due to certain circumstances, this printer had already been pulled apart.
The first thing I needed to do was get my printer running so I could plug my logic analyser in and look at the signals, the problem was that I was missing one ink cartridge so the printer refused to print, or do anything.
Due to my budget (jobless and about to start university) I decided to try and Emulate the missing cartridge, or all of them using one microcontroller, thus allowing me to move forward and using water for the print head instead of ink that stains.
Video of the finished result:
New updated video: (HD)
Step 1: Getting familiar with it
Inside the print head, there is a circuit board with pads mapped out that are an exact mirror of the pads on the ink cartridges and a ribbon cable that connects this board up to the main board on pins 1 to 6.
A quick look at the schematic for the main board reveals that pins 1 – 6 are named CVDD, CSDA, CRST, GND, CSCK and COI.
With these signal names I decided it would be best to draw out a schematic of the connecting board as it was not present in the service manual. This revealed that CSDA, CSCK, CRST have 100KOhm Pull-Down resistors, a bit unusual in my opinion as it’s not like I2C (uses Pull-Up Resistors typically 1.8KOhms to 47KOhms). The COI signal connects serially to the ink cartridges but on the end is shorted to GND. Curiously I tested the continuity of the pads on the ink cartridges and found that they are shorted, this means that when COI is grounded, all ink cartridges are present.