Hello Mars. I am also a part time reprapper, although not as active recently. On the reprap forum I post as the rocket_scientist.
Yes, it would be VERY nice if we could just stick a board into alignment jigs on a Mendel and lay down a resist mask. The problem is that most current designs use somewhere between 10mil and 5mil design rules. That translates to 0.127mm. I have made some glass nozzles for extruders, so I remember the current size. The 3mm raw material extruders have about 0.5mm orifices, going down to about 0.3mm. I know that some people are using a much finer gauge plastic 'wire', so they may have extruder nozzles down below 0.2mm, but probably not smaller than 0.127mm The next problem is that when you extrude the plastic above the copper surface, assuming the copper is perfectly flat across it's whole length and width to less than a single layer, when you squeeze out the plastic filament, it MUST press hard enough against the copper to bound, and that will make it spread sideways just a bit. SO to reliably make 5mil lines and spaces, you need about a 0.08mm extruder, and stepper motor absolute precision to match. I don't think the current repraps are quite that good yet, but if you tighten one up and use microstepping on the stepper motors, you might be able to achieve it.
As for removing the resist after etching, if PLA can stand up to the etchant, than we all know that boiling water will remove it, followed by a little acetone to remove any residue.
The best part, particularly for us old timers still using through hole, would be to mount a small DC motor in place of the extrduer to drill all the holes. And of course the same device can be used to mill out the copper traces for isolation well pcb, but now you are talking about going from 34mil drill bits to 7mil diameter carbide end mills, which are much more fragile and expensive. Still, it is possible to make boards this way, but initially not at full toner transfer resolution.
I hope this helps.
Mike
(rocket_scientist)
--- In Homebrew_PCBs@yahoogroups.com, "Mars Bonfire" <mbonfire@...> wrote:
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> I must admit I enjoy reading this group, not the least of my enjoyment from the diversity of ideas on how to make pcbs at home. I am a toner transfer practitioner which suits me fine. I have done photoresist many moons ago when I had access to the coating chemicals.
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> Currently I am working on building a 3D plastic printer (google reprap if curious) and it occurred to me that printing plastic (or a meltable material that would resist etchant) on a pcb would be yet one more way to put down etch resist...any I won't bet someone has not already tried it. Now you won't catch me trying it but...any thoughts?
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