Actually just an adaptation of an existing guide to the better-available Lexmark E360d
I have been using the modified printer for a while now and I'd like to leave some comments on the actual usefulness of the project. PCB manufacture has been decreasing in its price, so I rarely use the “haxmark” anymore. It gets reactivated when I need a board fast and it does a very decent job.
If you already know how the process works, feel free to skip to the next section. For those of you who don't want to go three links deep to the full text, here's a short overview of how a regular laser printer can be used for PCB manufacture:
The goal is to be able to etch the PCB straight from the printer. I use regular copper-clad PCB material without photo-resist, so ordinary toner will be the etch resist. Basically the goal is to let the printer print on the PCB just the way it would print on paper. Regular toner is really durable, so there won't be any surprises when the PCB is bathed in chemicals.
From a mechanical point of view there are quite some modifications to be made. Because PCB material is a lot thicker and more rigid than paper, the printer's feed mechanism won't work and large parts have to be removed. Instead, the PCB material is placed on a thin metal carrier, which is pulled in at the front and ejected through a newly cut slot on the back. The optics and drum are still in place and the toner is transferred onto the copper.
Because a lot of the mechanics are missing, a lot of sensors are, too. Normally, the printer's brains will get signals as the paper is passing through the internals and will stop everything when something unexpected happens. Thus, if the printer should actually print and not only produce paper jam errors, these signals need to be simulated. A small PCB with a microcontroller functions as a replacement for all the removed mechanics by feeding the signals to the printer's main PCB it expects.
However, the printing has to function without the fuser. It wouldn't provide enough heat and certainly have problems with the thickness of PCB and carrier. The PCB exits the printer with the toner particles stuck on solely by electrostatic forces. Those are stronger than you might think, but obviously not string enough for the etching process. A simple solution is to place the PCB in acetone vapour which doesn't degrade the printing quality at all but effects great durability.
And that's pretty much all it takes. Etching works as it always does, but the process before it is greatly simplified.
I design my PCBs in KiCAD, but the CAD program of course doesn't really matter. These are my steps for etching a PCB from start to finish: