Homebrew PCBs

Stefan Trethan wrote:

> 
> I did execute the described experiment.
> 
> i taped a stripe of aluminium foil on one half ot the page.
> then i printed a page with X all over.
> cut the power as it was halfway through.
> 
> 
> Inspection of the srum shows just what i thought.
> 
> before point of contact:
> clear image, thick.
> 
> after point of contact on paper half:
> very faint residue, if you don't know what it is you couldn't read it.
> 
> on aluminium half:
> about half the amount of toner still on the drum.
> image printed on aluminium foil but not as dense as on paper (holes too).
> 
> 
> for me this shows my guess with "charge shorted but some toner still 
> transferring"
> was very close, even the 50/50 is about what i see here.
> 


   After reading through the HowStuffWorks, the copper/aluminum being conductive 
is the problem.  The paper isn't oppositely charged from the drum.  The toner is 
positive, the drum is negative to pick up, and the paper is then more negative 
to attract the toner from the drum.  The paper has first the charging corona and 
then another discharging after to unstick the paper from the drum.  The paper 
underneath will keep the copper from directly shorting the charge/discharge 
wires as long as they are on the underside, but the copper on top will equalize 
the charge on that side or short if they're on top, so once it gets to the detac 
wire it'll have both neg and pos and be whatever shade of neutral the relative 
charges on the wire make.  50% less sounds about right, they may not need as 
much opposite on the detac just to unstick the paper.

   Note with a copper board there would be no tendency to wrap around the drum, 
you could remove the detac wire and possibly get an excellent print with a fully 
charged copper plate, just watch out for the static charge near any electronics 
afterwards since it's not being discharged during the printing.

   Now I really want to find a good upright printer as in their drawing that has 
a straight mechanical path with a little case modification.  I'm now fairly sure 
the direct to copper can be made to work, and the fusing part is just a matter 
of heat and slower speed to get that working so should be easy enough.  As good 
as toner transfer is damn it'd still be nice to not mess with the paper.  The 
amount of toner etc on a normal page would be fine if it were all on the copper 
and fused well, so I don't think other mods would really be necessary.

Alan