Stefan Trethan wrote:
>> The drum coating is a high insulator to hold the charge in place and
>>then
>>have the laser only discharge parts of it. Should be a much better
>>insulator
>>than the corona wire charge can do by default. Even though the charge
>>'equalizes' it may still do so by pulling the toner and charge off the
>>drum,
>>which is clearly how it happens for it to work..
>>
>>
>
> I think very along this lines.
> however in one of the recent links provided there is written about this:
>
> if the detach wire would have a dc voltage it would smear the image.
> so it has a ac voltage.
>
> Now, i really wonder a lot about this statement....
>
> But my IIID has no detach, and we need none because the copper is flat.
Hmm maybe that is why the ozone smell and feel on some older laser printers,
no discharge wire.
>
> Still, the charge equalizes, and is a dc charge (of course).
> so why then should a dc detach smear the image and a dc transfer not?
Since you don't know how much image you have exactly, the AC does a better
job of discharging since you don't know exactly how much charge to discharge.
It's just more 'guaranteed to be close to evenly discharged' than an opposite
charge vs not exactly known incoming charge. More less thought in the process
than great advantages I think, although a solid charge might move some toner a
bit etc.
>
> I somehow doubt the toner density can be increased so much that there is
> enoug
> even if only half is transferred. (nice sentence...)
I don't think it's needed, even half of what's on a page is fine to protect
the copper if it's even and well adhered. I've had plenty of prints where parts
had half still stick to the page but still etched fine. I think if we just get
even most of a normal print on the copper it'll be great, no real need to
enhance the amount over that. I'm thinking more towards getting it to print
right than making it more now.
>
> I wonder if the charge needs to be really high, i do not know how much of
> the 6kV
> of the corona wire is effectively charged onto the paper, or drum.
> maybe a lower voltage works?
>
> the second thing is how to charge the pcb, maybe a piece of wire dragging
> over
> the surface just before the drum may work.
> maybe also a piece of aluminium foil taped onto the surface would work...
>
> (I measured aluminium foil and both sides seem to have no oxyde at all.)
>
> All strange and funny things going on here and i do not really know what
> is to be
> done now. i will look out for a printer and think in the meanwhile..
>
> maybe we should try to convert a printer to get the pcb charged and see if
> there
> is more toner transferred....
>
Yep I'm thinking the same things, just a drag contact and maybe even try the
charge well over normal with a seperate supply. Shouldn't take much of a supply
since it's just charging to a static charge. May take some experimenting to see
what actually works but it looks like it should work well.
Alignment for doing double sided on a single board might be a bear though.
But still is no real problem at all. Get the thin laminate stock and print 2
boards, then just drill two corner holes for alignment and glue together and
drill etc as normal with your own laminated board. Should be easy enough, but
much of my stuff is designed single sided surface mount now anyway for ease of
construction.
Alan