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G8MNY > TECH 15.08.05 00:11l 115 Lines 5712 Bytes #999 (0) @ WW
BID : 58048_GB7CIP
Read: GUEST OE7FMI
Subj: Xerox Copier Principles 2/2
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Sent: 050814/2218Z @:GB7CIP.#32.GBR.EU #:58048 [Caterham] $:58048_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Comments Dec 04)
DRUM PROCESS
a/ The drum is electrostaticly discharged with a row of small lights.
b/ Then it is "charged up" with static from the nearby corona wire (10kV?).
c/ The well focused & in step light image falls on the rotating drum.
d/ The static is discharged were the light falls producing an electrostatic
drum image.
e/ This passes very close to the toner hopper where the black particles are
picked up on the charged areas to make a toner image.
f/ When the drum & image reaches the paper another static charge under the
paper encourages the drum to drop the toner image.
g/ The drum then passes a soft rubber scraper to remove surplus toner.
Depending on its diameter, the drum may rotate several times for a single sheet
of paper. The initial static charge, & image light level both affect the
contrast & are normally varied to get the exposure correct.
Electrostatic fields actually get stronger with finer images, so fine detail
(other than focus, unmatched speeds, toner particle size & paper grain) is not
a problem for the Xerox process, compared to some digital copiers.
PAPER HANDLING
Movable rubber pickup rollers in the paper box as well as & paper switch gates
for manual feeds all need sensors to make sure the paper is in the right place
before the copy process can start.
The flat feed tractor sometimes use fan suction to gently handle the paper &
loose toner image into the fuser unit.
As all these are very mechanical & liable to paper dust they do give trouble,
so clean them as needed with damp cloth/alcohol (meths).
FUSER UNIT
This is the last part of the process 8/, it has a heated roller tube normally
with a 1KW lamp inside. It is maintained around 100øC, THAT IS HOT & it is
reaching the running temperature that takes up the initial warm up time.
A seconds rubber pressure roller makes sure the outgoing toner image is fully
fused to the paper.
Often an economy mode is used to reduce the fuser temperature, but then it will
takes a minute or so to be ready to copy. The temperature of the fuser unit &
feed speed, determine what type of clear acetate OHP material that can be used.
LASER PRINTERS
These work much the same as copiers, except a laser & mirror scanning system
erase the charged drum with the image to form the white areas.
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Comments from Harry M1BYT @ GB7CFR...
Over time and usage the pickup rollers can become hardened and glazed by the
passage of the paper. If simple cleaning does not help and they retain the
glaze indicated by paper misfeeds, then they are quite cheap to replace though
often difficult to get at inside the works. One solution which has worked
several times for me, is to clean the rollers with 'sticky stuff remover'.
This solution seems to both dissolve the glaze and soften up the rubber to
make it as good as new, often without a great deal of dismantling.
Horizontal lines across the width of the paper and similar regular defects,
can be diagnosed by measuring how far apart they repeat. The repetion rate
will exactly match the diameter of one of the rollers, the drum, or the heated
roller in the paper path.
There is a school of thought which suggests the fine toner particles will pass
straight through a vacuum cleaner dust bag, so the use of a domestic vacuum
cleaner might not be advisable. Cold water on a cloth is the recommended
method of cleaning up spillages.... Not hot, as this melts the toner fixing it
and you will then never get it off. The same applies to clothes which has had
toner spilled on them, wash them well in cold water first, never hot.
The fuser rollers often prove to contain nothing more than a simple tubular
tungsten halogen lamp as the source of heat in the middle of the roller. Often
these can be bought much more cheaply as sold for there original purpose at an
electrical dealer, a T/H lamp as used for lighting up your drive.
Grades of toner can vary from machine to machine, but it is often possible to
refill a œ60 original toner cartridge combined with drum several times at a
cost of œ15 per fill. The process typically involves hot cutting a hole in
main hopper to refill it and cutting a second hole to drain the waste toner
section to drain that. Drilling can allow small fragments of plastic to abrade
the drum, so the method is to make the hole(s) with something similar to a
heated apple coring implement (ask SWMBO). A metal one rather than the plastic
ones which do tend to melt :-)
Once the draining (usually every 2nd refill) and the refilling is complete,
the hole is covered with sticky tape or similar.
The more capable printers often contain a fan and filter to prevent toner
escaping into the office atmosphere. This might need to be cleaned or replaced
at regular intervals.
As regards buying and running a laser printer, the best and cheapest to run
are the ex office machines. These can often be had for simply taking them
away, they are built to last and the cartridges are often 3 or 4 times the
size of the home lasers and cost not much more. Larger paper capacity,
probably more capable, reliable and much faster than a home model. Their sheer
size need not be a problem, you can put them out of the way if they have a
network card or install an after market network to parallel printer adaptor,
plus run a LAN.
Mine lives in my shack in the loft, always on standby, available to any of my
PC's on the LAN. Just one machine to be fed watered and maintained very
occasionally.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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