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Drum unit
replacement.
The drum unit contains Developer, Drum & Charge rollers.
Developer is rugby ball shaped carbon granules of a
predetermined size. Toner is added to the developer mix from the
toner cartridge, toner being negatively charged it is attracted
to the positively charged Developer granules.
Magnetic Brush / Development Roller
The developer and toner mix is agitated within the drum unit
where the developer being ferrite based it is attracted to the
Magnetic Development Roller, the Doctor Blade / Developer blade
limits the amount of Developer on the Development Roller.
 Monitoring
the Toner / Developer mix level
During this stage of the process the machine senses whether
there is enough toner in the mix and adds more if necessary.
This is done by inducing a charge in a coil of wire, when a
magnetic developer is rubbed against a coil it induces a
electrical charge in the coil. If there was no toner in the
developer mix then the developer granules would be closely
packed together on the development roller and would induce a
high charge. When toner particles are present in the mix the
developer granules are forced apart and a lower charge is
developed, this is how the machine maintains the correct toner
levels. As toner is transferred to the drum to form the image
the toner sensor voltage increases and the toner motor turns on
to add more toner until the sensor reaches its optimal value.
 Why
do I need to change it?
During the life of a drum unit the constant agitation of the
developer wears the granules turning them from diamond shapes to
rugby ball shapes. This then creates an air gap between the mix
and the toner sensor, because there is a gap a lower charged is
induced in the toner sensor coil which the machine interprets as
a high toner concentration therefore toner is not replenished as
required, the result is wishy washy solids, this effect will
intensify as wear continues. You will also find that the machine
starts to soot up with spilt toner that has not been transferred
to the drum properly.
OPC Drum Surface
The photo-conductor drum is a light sensitive coating on the
drum surface, this surface gradually gets worn by paper passing
under it, as it wears its sensitivity reduces and so it attracts
less toner, this compounds the developer problem.
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New drum is just like a sharp pencil, sharp
lines, strong colours. |
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Old drum is just like a blunt pencil, fuzzy
lines, weak colours. |
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 Fuser
Unit Laser
printers fix the toner onto the paper using heat and pressure
(Fuser Unit). The system employs two rollers the top roller
(heat roller) is a hollow aluminium roller coated in Teflon (the
roller is coated in Teflon to stop toner sticking to it).
Through the centre of the heat roller is a tungsten halogen
heater lamp (similar to a cooker) the lamp heats the surface of
the heat roller to approx 200 degrees. The fuser unit monitors
the temperature via a thermistor and turns on and off the heater
lamp. The lower roller (Pressure Roller) is rubber and is
constantly pressing against the heat roller.
 A
bit about paper Laser
printer / copier paper has a 5% moisture content, this is why
the wrapper is coated in wax to stop moisture penetrating, as
soon as a ream of paper is opened it will absorb moisture until
equals the atmosphere (which can be 25 – 30%)
Photocopying or printing on paper with a high moisture content The
hot roller runs at a slightly higher temperature then the lower
pressure roller, so the top side of the paper nearest the heater
roller will get hotter causing it to curl due to shrinkage. Also
the moisture absorption is not constant so shrinkage occurs at
different rates causing a corrugated effect. This is not cause a
problem on single sided copies. But if you try and print or copy
double sided, you will have several issues, jamming, creasing
and print rubbing off.
· Jamming
– because the paper does not enter the fuser unit straight.
· Creasing
– because the pressure roller will try to crush the curled
corrugated paper flat.
· Print
Rubbing Off – Print will rub off because the high moisture
content has stopped the paper reaching 179 degrees, the fusing
temperature of toner.
Example I
was asked to repair a copier that appeared to be reducing an
image on the second side. The image had a square border 1cm from
the edge of the paper, when you held the double sided image up
to the light it was obvious that the second side was 3mm smaller
then the first side. A lot of head scratching and checking was
done. Finally I held a copied sheet up against an un copied
sheet of A3 paper the copied sheet had shrunk by 3mm during the
copy process. Because toner is laid onto the paper prior to
fusing the first side was correct, during fusing of the image on
to the first side of the paper had shrunk.
Moral of
the story If
you want to a reliable machine ensure your paper is dry.
For the best results make sure the paper is recommended for
double sided copying. If the paper has an arrow on the end the
packet it usually means single sided use, it may well double
side but you may have problems. When you open the paper, open
the reams carefully from one end, any paper left in the packet
can be protected by folding the end of the packet back over and
putting the paper back in the box. This is especially true of A3
paper that may hang around for months before being used.
 Toners
Compatible ! why Oki machines work well with our compatible
toners
Oki machines are one of the few manufacturers whose toner
cartridges only contain toner. The Drum unit that is replaced
every 3 toners contains the developer, cleaning blade and drum.
The Oki toner supply system also suits compatibles due to it
being gravity fed system. A roller in the base of the toner
cartridge feeds toner into the drum unit as and when required.
We have been supplying compatible Oki toners for 4 years with no
detrimental effects. See our total
cost of ownership page
to see how you can save 33% on your running costs.
Toner Compatible? should I use them!
People assume a toner cartridge just contains toner, this is
only true in a few cases. Most toner cartridges contain three
components.
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Toner, the powder that is
fused on to the paper to form the image
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Developer, a graphite based powder that
regulates the amount of toner reaching the paper (similar to
the nib of a fountain pen).
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Drum, PCU, Photoconductor, a light sensitive
drum.
The reason compatible toners vary in price and quality so much
is down to the cartridge?
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Has it just been refilled
with toner.
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Has it been refilled and the Drum and
cleaning blade replaced.
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Has been remanufactured with new toner,
drum, cleaning blade and Developer.
The only way to know is to use the cartridges and find out what
happens!
The cartridges we sell are remanufactured cartridges, that we
will warrant is being fit for purpose, NO compatible
cartridge will work as well as an original.
If you
would like to book a service call ring 01293 537827 or email sales@digital-office-solutions.co.uk
| Local
printer sales, supplier new, refurbished, reconditioned
and used Crawley, Horley and Gatwick |
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DOS are a local printer
repair specialist, our experienced mobile technicians
offer an on site printer installation
Printer sales, supplier new, refurbished, reconditioned
and used Crawley, Horley and Gatwick, Digital Office
Solutions offer printers, laser printers, wide format
printers and plotters from Brother, Canon, Epson, HP
Hewlett Packard, Konica Minolta, Kyocera Mita, Oki,
Ricoh and Samsung in Crawley, Horley and Gatwick, West
Sussex & Surrey area. |
|
Printer sales, supplier new, refurbished, reconditioned
and used Crawley, Horley and Gatwick, Digital Office
Solutions offer printers, laser printers, wide format
printers and plotters from Brother, Canon, Epson, HP
Hewlett Packard, Konica Minolta, Kyocera Mita, Oki,
Ricoh and Samsung sales, supplier new, refurbished,
reconditioned and used Crawley, Horley and Gatwick in
Crawley, Horley and Gatwick, West Sussex & Surrey area. |
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