--- In
Homebrew_PCBs@yahoogroups.com, "Steve" <alienrelics@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "James Bishop" <bishopaj@> wrote:
> >
> > This gave me an idea.. I wonder if it would be possible to replace the
> > laser diode in a laser printer with a uv one, and then run a
> > sensitised board through in place of the drum..
> >
> > What do you guys think? Am i crazy?
>
> Not crazy. I recall a past conversation on this but don't recall the
> outcome.
>
> I suspect exposure time would be a problem. Photoconductor drums are
> very sensitive, whereas photoresist is not.
>
...
> It seems that direct inkjet conversion would be much simpler,
> comparatively.
>
> But don't let anyone stop you from trying! There used to be lots of
> nay-sayers about direct inkjet printing, some of them quite vehement.
> All it really took to happen was the advent of pigmented ink and for
> someone to keep trying.
>
> Steve Greenfield
>
I too think that converting a laser printer would be difficult for the
reasons given. A steered & focused laser ∗could∗ work. The refinement
of the technology physicists apply to manipulate Bose-Einstein
condensates & quantum entangled subatomic particles makes etching PCBs
seem quaint. But it seems to me that the laser printer itself takes
too different an approach to printing to be reasonably modifiable. I
∗would∗ like to see someone prove me wrong, though!
What I was thinking of when I mentioned this was mounting a small
laser diode from a DVD burner in or in place of the inkjet head in a
salvaged printer, putting the whole works in a light proof box
(probably made out of black foamcore) and 'printing' directly on
photosensitized positive or negative type emulsion.
Thinking further about this, it seems to me that the printer
(depending on the model chosen) would probably have the necessary X &
Y resolution. The big advantage would be the ability to use the
existing printer driver for control. The manufacturer has almost
certainly done a lot of tuning to manage microstepping, motor
resonances, etc. The hard part might be fooling the print driver to
think that it has a functioning cartridge in place with a normal
supply of ink.
The distance between the print head and the emulsion would likely be
similar to but not the same as the gap between the DVD head and its
target. The focal length of the diode's optics is probably not
optimal. What may be important is the spot size at the emulsion. Too
fine a focus might cause problems, too. The finer the focus the more
optical energy is deposited in a given volume of emulsion. But too
fine a focus might create a halftone effect, depending on its
dispersive/absorptive properties.
Rotating media use closed-loop servo mechanisms to control tracking
and make fine adjustments. I believe they are working with much
tighter tolerances than we are, but I don't know. Tuning the
intensity of the beam could be managed with simple pulse width
modulation of the laser. I'm not sure what else might be involved, it
is probably time for some empirical tests.
-- Dave W