Here is how our printer will work: we type any message in terminal then the message will be printed (as dot matrix) and after the message is printed the program will wait for another message.
For this magnificent printer you will need:
1) 1 x Arduino (I've used the Duemilanove)
2) 2 x H-Bridge (SN754410)
3) 3 x small dc motors from any cd/dvd drive
4) 3 x switches from the same cd/dvd drive
5) A pen or marker
7) Rubber string
9) Stick with round rubber like the rollers in a real printer, the wheels from a toy car should work.
10) Acrylic, wood or whatever you have to build the structure.
11) 5v and 9v power supply
If you have an old printer you can use its structure and save some time to build one.
Once you have all that is time to build the structure.
Step 1: Build the structure
All you have to do is to mount a "U" Structure and add two tubes where our printer's head will move, also add the supports for rollers and the sheave.
As said before, if you have and old printer you can use it and skip this step.