Laser printer and a drum?

[Arthur Entlich]

As far as I am aware the difference between a laser and a laserjet is
that HP uses the name "laserjet" for their product line of laser
printers. In other words, a laserjet is a laser printer.

However, HP uses a self-contained cartridge system which has the toner
cartridge and the drum in one unit and you replace both when you run out
of toner (unless you refill the cartridge, using the same cartridge, and
therefore the same drum). This practice is used by some other brands as
well, but some are still using the separate toner and drum, or even
toner, developer and drum sections, although the later is fairly rare
these days.

One other comment. Six years ago, laser printers were being sold with a
different business model. Generally, that long ago, the printers were
selling for a bit more to acquire, and came with a full toner cartridge
and often a heavy duty drum. Today, laser printers, like inkjet
printers tend to be sold less expensively, but come with partially
filled (or starter) cartridges and with drums designed for one or two
refills before degrading.

The whole printer industry has gone to having the profit tied up in the
consumables like toner, ink, cartridges, drums, and paper and
supplementing the printer sale from those later sales.

Art

If you are interested in issues surrounding e-waste,
I invite you to enter the discussion at my blog:

http://e-trashtalk.spaces.live.com/

 

[Arthur Entlich]

There have been a number of incorrect statements regarding the internal
function of laser printers. I'm sure the best of intentions were the
motivation, but a number of factual errors in recent postings leave me
wishing to correct some notions.



Laser printers need a surface which is sensitive to light and which
changes static charge based upon exposure to light. The light source is
often a laser beam, or LEDs. Typically, this surface is coated on a
cylindrical drum made of aluminum, although some units use a transfer
belt which is a long film like belt which has a similar surface.

When the drum or belt is properly charged, the parts that will be
printing an image acquire a static charge which attracts the very finely
ground powder called toner. It clings to the surface of the drum of belt.

There are several different ways that the toner can be made available to
the drum surface. In some cases, the toner is presented at very close
proximity to the drum surface by a roller which is saturated in the
toner, in some cases, the toner contains very fine iron particles which
the toner is integrated with and this materials sticks to a magnetic
roller and the charge on the drum pulls in to the drum surface. In
older systems, the iron particles were a separate agent which the toner
coated and only the toner transfered to the drum surface, leaving the
iron particles behind where they were reused.

Typically, on newer laser printers, the drum is only about the diameter
of 1/4th of the paper length, so the drum surface is charged and toner
coated about 4 times to produce an image on one sheet of paper.

The way the toner gets transfered is a mixture of pressure and use of
static charges to transfer the toner powder from the drum to the paper
which passes directly in contact with the drum. Not all the toner comes
off, however, so a flexible wiper or squeegee removes the excess toner.
This may then go into a waste toner hopper, which is sometimes part of
the cartridge, or the toner may simply be recycled and mixed with the
rest of the unused toner.

Over time, the drum may lose some of it's light sensitivity, may get
damaged from bad paper feeds, bits of grit, poor toner quality, staples,
etc, may get worn from the continual wiping to clean it, etc. Some
companies do refurbish this drum by removing the old surface down to the
metal and applying a new light sensitive surface. Some companies
rebuild the cartridge and may replace the drum with a new manufactured
one, while they also refurb other components in the cartridge and then
refill it with toner.

In the final stage of printing, the paper, now containing the toner, is
passed through some more rollers, including a highly heated Teflon
coated one. This is called the fuser,a sit fuses or melts the toner
onto the paper surface. Some printers have a cartridge or wiper with
fuser oil on it or in it, so that the toner, as it melts, doesn't stick
to the heated roller or other components. Usually, this roller is
heated by a halogen lamp which sits inside the aluminum fuser cylinder.

With color laser printers, some have 4 drums and go through this process
4 times, usually placing each color in sequence onto the paper but only
doing one fusing process per page. However, some lay all the color
toners down on the transfer belt and then transfer that final image to
the paper before fusing. Those models usually have one transfer belt or
drum rather than one per color.

I hope this helps to clarify some of the internal operation of a laser
printer (photocopiers work similarly). As a disclaimer, I have
simplified things regarding issues like how the static charges are used
to get the image to the drum and then the paper.


Art


If you are interested in issues surrounding e-waste,
I invite you to enter the discussion at my blog:

http://e-trashtalk.spaces.live.com/

 

[postretro]

Then you must be almost right then <BG>

The HP/ Canon (the originator) types - and 75% of all, have a toner hopper
with a magnetic roller which dispenses toner in a thin toner film. The
static image on the drum opposite has an attraction for the toner which it
pulls across the few mm gap to form the print image on the drum. These and
the fuser roller close to one end of the paper tray are constantly turning,
and the drum polarity changing as the paper has the toner heated to 350
degrees, and pressed into the paper.

How can you do duplex (two sided) printing without melting the toner on the
front of the page? The toner also polymerizes as it is fused, and won't melt
a second time at that temperature.

These technical marvels were first put together by Xerox in the 1970s, who
'only marketed the laser printer inside Xerox' according to one Xerox
propeller head. They also developed, but never originally marketed the
graphic user interface - the DNA of WP and desk top publishing.

Canon missed the boat by licensing the product to HP in the 1980s which
seized control of the market by the simple means of giving any software
developers, all their proprietary driver manuals and floppy diskettes for
free.

These are two little examples of why sales and marketing people make more
money than technical staff.

 

[Gregg Hardin]

On Sep 8, 2:15 pm, "Ato_Zee" <[email protected]> wrote:
> > If you are looking for LASER then all laser printers require TONER and
> > DRUM for laser printer to work.
>
> Some toner cartridges have plenty of toner but the wiper/doctor/scraper
> blade that returns surplus toner to the hopper fails early in life, so
> you soon get dark smudges and repeated images spreading
> down the printout.

I realize I'm slightly off topic with this comment, but laser printers
seem to be a pain to operate with all the potential failures and
expensive parts. The inkjet is so cheap and reliable if you have a
cheap source of ink to refill. The only real advantage I see for the
laser is where people let the printer sit unused for months.

It all depends on how much you print and what you want to do with the printer and the quality of the prints that come out. I have a black and white laser printer that I absolutely love using. I have used up a drum as I have printed close to 12000 pages over the 7 years that I was a student. I haven't heard of an inkjet lasting that long. the cost of buying a laser printer is getting to be less as the technology improves. Inkjets spray on a fine mist and lasers on the other hand, kind of heat up the toner and fuse it to the paper. I am a technical writer and I need good quality documents. Many businesses use lasers because the quality is better than inkjet printers. LIke I said it all depends on the quality of the work and how you want your documents to look.