for some reason i needed a mobile printer one day. it had to be movable, reliable and plug'n'print. to be more specific here's an unordered list of what it should be able to do:

- print on endless paper
- plug in into an existing network (with dhcp configuration) and print all new mails from a specific account each 10 minutes
- be heavy enough not to slide around all the time
- be light enough to be easily moved around
- no configuration, no login or whatever on startup, just push the button and it works
- easy maintenance (in case e.g. the cartridge is empty)
- low cost

Step 1: Setting Up the Printer

(sorry no pic. i'll keep this step short since i don't want to go too much into technical details - you guys who know linux are able to do this better anyway ;-) )
after purchasing a cheap old dot-matrix printer on ebay and checking for the matching drivers i installed a very basic debian system (non-graphical, just textbased) on an old computer i had lying around (400 mhz, 250 mb, 4 gb from 1998). configuration was easily done in cups via a textbased www-browser on the machine. as you can see here i'm quite a noob - didn't know how to do it better (but i'm sure there is a better way). after setting up and configuring a mailclient i wrote a simple script that invokes the client, converts the incoming mails the way i needed them and sends them to the printer. a cronjob then runs the script every ten minutes. so far so easy.

Step 2: What Not to Do: Start/stop the Whole Machine With a Switch

everything had to be as easy to start and stop as possible. starting it is easy: press the start button of the computer. the machine will boot and verything runs fine. the problems start when one wants to stop the machine: pushing the button again turns off the machine, but it also can crash the harddisk. at the moment the machine is still running that way, but any hints how to do it better would are greatly apprechiated (shutting down just with a single button)!

Step 3: Disassembling the Hardware

after measuring the dimensions of the printer and the parts of the computer i decided to mount everything on a single piece of mdf with wheels on the bottom. i wanted to take away the original cases to improve cooling. this was easy with the computer: take out a few screws and you're done. the printer was the harder part to disassemble (and, of course, to be able to reassemble it again without it's case).

Step 4: Reassembling and Mounting

after disassembling the hardware got mounted on the bottom of the case. cables and switches were added to allow everything to be put inside the case and to have just a switch and a wall-plug on the outside.

Step 5: Building the Case

the top part of the case was built with mdf and dowels. since i don't have a drill-stand with possibilities for adjustment i just wrapped a tape around the drill to know how deep i can go without going through.

Step 6: Wheels

after drilling all holes needed the wheels were mounted to the bottom and loose cables and the transormer of the computer were fixed with cable ties.

Step 7: Test-assembling

next thing to do was to test-assemble the whole thing to see if everything is in place

Step 8: Cutting Holes

test assembling was successfull so i took everything apart again to cut the holes for the fans, switches and the wall-plug

Step 9: Paper In- + Outlet

at this point i ran into troubles: i needed to makes slots for the paper transport through the printer. thinking i would be able to do it simply by using a milling machine i ended up with a slot like you see in the picture below.
thinking over it again i decided to add some kind of tracks to the inside of the panel to keep the milling machine in line. this worked out perfectly.

Step 10: Glueing

glueing it alltogether was quite easy. i used cheap paper tape to keep it all in place.

Step 11: Assembling and Testing

the last thing to do was to screw some pieces of wood to the bottom to prevent the top from sliding around. after this everything was put together and the printer was tested successfully. to keep it as nice as it was the case was painted (clear) afterwards.