RE: [CAD_CAM_EDM_DRO] Re: 3D printer fun with powder

In a copier the roller is in a cast plastic housing with a surface that if
continued would intersect the roller. The blade sits on this, mounted on
slotted holes so that a comparatively large movement off the blade on the
slots is a very small movement of the gap.

The roller is a tube with a magnet inside, the toner in this area also
contains developer which is finely ground iron filings. As the roller turns
the iron fillings stand up to form a brush which holds the toner powder,
presenting it to the photo conductor drum where it will stick where it is
charged.

All we do for setting the doctor blade is rotate the roller and watch how
the iron fillings stand, it it's too low you get patchy bald areas, too hi
and the brush is clogged with toner, just right and you see a nice smooth
black carpet like brush. (or other colour for coloured toners)

Most of those I have worked on the doctor blade is metal, these would be
Xerox, Minolta, Fujitsu, Epsom and a few others I don't remember. There are
plastic scrapers people will also referr too but these go on the drum, there
are two types, a very soft plastic that always wipes the drum, and a tougher
one that scraps thick junk off the drum which can occur with some electrical
faults. They both scrap excess toner after the image is put to paper and
drum charge erased which is pulled off into a collector bottle, this will
contain a little amount of developer (iron filings) but should not be very
much, you want the developer to remain in the toner unit so only toner needs
replacing and developer on rare occasions, but if the doctor blade is wrong,
or the magnet in the roller incorrectly adjusted the copy will look
reasonable, but the developer will erode at a massive rate.



I don't know whether that will help raise any ideas at all, but that's about
whats in a copier.



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: 22 June 2007 05:30
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: 3D printer fun with powder



Graham Stabler wrote:

>
> I tried a blade to scrape the roller last night, it is rubber and
> normally used for grouting tiles. I'll try it again with the bigger
> roller (now installed but I'm going out). I'll also try some mylar as
> per Jon's suggestion.
>

The doctor blades on laser printers are very carefully cut so
they leave a .005" or less gap all across the roller. I can't
even begin to imagine how they do this with cast plastic parts
in a mass production factory.

Also, controlling static charges is a big deal. Laser toner is
conductive, so it won't stick where it isn't supposed to. They
have various grounding connections on various things to prevent
parts of the machine from charging where it isn't wanted. If
your powder can charge up, it may be necessary to ground things
to prevent the roller and other parts from picking up a charge.

Jon





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