Alan King wrote:
> 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
>
>
>
>
>
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>
> Basic operation, in most laser printers, is based on electrostatics a
> old art, thanks to zerox. The drum or image roll is coated with a
> photoconductive coating. Which is charged with a high voltage as it
> rotates. The laser beam is modulated with the data image and shot
> onto the drum. That beam causes the photoconductor on the drum to
> conduct and discharge thru the coating to the drum ground. The next
> step in the drums path is the developer which lightly dusts the drum
> surface with toner. While there are several styles in this
> operation, the end result is the toner sticks to the drum where it is
> held by the remaining charge. Then next step is the image transfer.
> Or whats known as the transfer station in the drums path. The drum
> now meets up with the paper, both moving at the same speed so the
> image remains stable and clear. With the paper between the drum and a
> high voltage charge on a corona wire, the toner jumps off the drum
> thru the air toward the charge and ends up landing on the paper. The
> paper then travels to the preheater and into the fuser area of the
> printer and is pressed into the paper using a hot roll along with a
> backup roll. The hot toner melts into the paper. What us home pc
> makers are trying to do is keep the toner from sticking to the paper
> so well. Fuser oil or coatings on the paper keep the toner from
> locking down. Getting that drum image transfered to a sheet of
> copper will be a feat. The copper has to be moving at the same speed
> as the paper would be. The electrostatics for image transfer are
> critical for focus. The sheet of copper will be like a brick wall to
> the corona wire charge. After transfer takes place the left over
> toner and charge have to be removed. Sometimes another corona wire
> with a diffrent charge is in the drums path, some times a cleaner
> station to brush the left overs of the image off the drum. Then the
> drum is ready for a repeat for the next scan from the laser. While I
> don't know how to get that image on to a pc blank, I do know that is
> won't be easy or quick.
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