Display article   Subject:  Laser Accessories Life Cycles
   04/30/97   19:18:42


LASER ACCESSORIES LIFE CYCLES

Many questions have come up concerning the life of laser toner
and other replacement kits.  Listed here are the "published" life
times of the products we sell.  When considering these life
times, you must be aware of the many different things that can
severely affect these page counts.

How is Life Measured?

First, each manufacturer has their own measurement.  It is
usually expressed as "xxx copies at x% print using x type of
paper at xx-xx degrees temperature range with a humidity of x%
using the built in default font."

This way of measuring enables the manufacturer to be consistent
from one time to the next.  This is the only way to accurately
predict the number of pages.

You can see right away that there are going to be varying numbers
achieved by different users simply because of the grade of paper
used, or the temperature in the room where the printer is
sitting, or the humidity of the room or paper when it is fed into
the printer.  Just by varying these three factors a user can
change the number of copies by as much as 50% one way or the
other.  You may find that some users get as few as 1000 copies
from an LP 1000 toner cartridge and that some get as many as
3000.

Toner and Toner Cartridge Life

One contributing factor is the length of the print run, which
means the number of copies that are printed right after each
other.  For example, writing ten letters and printing them each
as a separate print job is not the same as printing one letter
with a print instruction to make 10 copies.  The latter will take
less toner to accomplish and will deposit less toner in the
spillover tray (Kit B on the LP 1000).  And even further,
printing 10 separate letters, one each day for ten days, uses
even more toner than printing ten separate letters without ever
turning off the printer.

To help explain this, think about what happens when you turn
on a laser printer.  It first cycles through a complete
revolution which does indeed activate the toner system to clean
it.  That causes toner to be used and that cleaned toner to be
deposited into the spillover tray.

Similar things happen when printing is done one page at a time.
Even though the toner that actually ends up on ten pages of paper
is the same whether it is printed one page at a time or all at
once, the amount of toner needed to accomplish the job is much
different.

When ten pages are printed continuously in one print job, each
page follows the other right through the system in a systematic
pattern without the drum having to accomplish extra cycles for
cleaning.  When each page is printed separately, the drum must be
purged of bad toner.  This is because it may have sat on the drum
for days since the last print job -- the printer doesn't know
whether the last print instruction was accomplished one minute or
one month ago.  Therefore, before each page is printed, this
purging is accomplished using more toner and depositing more
toner in the spillover tray.  In addition, each print instruction
that is separate causes the drum to turn additional turns which
also uses more toner.

To explain it another way, think about a painter that is painting
a room.  How much paint will be used if he paints it all at one
time versus stopping for a day between brush strokes?  Obviously,
the brush will have to be cleaned every day of the old paint
before starting the new day, which causes more paint to be used
and the garbage can to fill up quicker.

Paper Grade and Toner

Another important factor in toner usage is the quality or type of
paper used  (not to mention the size -- a legal sheet will take
more toner than a standard letter size).  This one factor is the
hardest to explain since the measurements are not something you
will run into every day.

There are several factors in paper that will determine how well
it reacts to toner:  weight, smoothness, porosity, opacity,
surface resistivity, stiffness, moisture content, thickness, and
dimensions.

If you want to give a technical specification on the paper for
the LP 950 for example, you would have to use:

Weight                       60-80g
Smoothness                   FACE greater than 20 seconds
                               (BEKK method)
BACK                         greater than 18 seconds
                               (BEKK method)
Porosity                     greater than 7 seconds
                               (BEKK method)
Opacity                      greater than 77%
Surface resistivity          greater than 5.0 x 10 to the 8th
Stiffness                    vertical greater than 17cm
Horizontal                   greater than 13cm
                               (CLARK method)
Moisture content             5.5% plus/minus 1%
Thickness                    75um - 110um
Temp/Humidity                20-25 degrees C
                             65 plus/minus 5% RH humidity


How confusing!  To achieve the maximum possible best printing
paper, you could use a special paper designed specifically for
Laser Printers.  This paper is not available through Radio Shack,
but is available from most office supply houses.  And -- it is
very, very expensive.  And even then there are several different
types of this special paper.

Most users use standard copier paper, while some use typewriter
paper, and some use their own letterhead.  The toner required for
the same amount of printed lines on each of these will be much
different.  Think about a smooth sheet of paper versus a special
(very elegant looking) letterhead on paper with a weave-like
look.  It obviously would take more toner to "fill in" between
the weave of the elegant looking special letterhead.  The more
porous a paper is, the more toner it will take to print a
character and the more toner will end up in the spill tray.  And
standard copier paper is sometimes the absolute worst at using
toner because it is generally very poor quality paper.

"at x print"

The other factor from our "measurement line" (the second
paragraph of this article) is "at x% print."  This refers to the
percentage of the paper that is actually filled with toner (i.e.,
how much is black versus how much is white).  For example, the
LP 950 is rated at 4% print.  This means that only 4% of the
physical page will be covered with toner.  Or 4% of the actual
page will be black versus 96% will be white or not printed on.

Don't let this measurement fool you into thinking that 4% isn't
much.  It is really a lot of the page considering that most pages
have margins on the left, right, top and bottom, and that there
are blank spaces and blank lines, and that each character only
takes up a small portion of the square that it prints in.

If you think in terms of a 9 wire dot matrix printer, for
example, the letter "c" uses 11 of 72 dots or 15% of the space to
create the letter.  So if that "c" was printed on every possible
space on a piece of paper, the "print percentage" for the whole
page would only be 15%.  Now take into account the margins and
spaces of a normal letter and you get that magic 4-5% number that
is used in most laser measurement specifications.

With the 4-5% above in mind, it should be fairly obvious that
there are several factors which can alter the page count from a
toner cartridge.

1. Any graphics on a page will lower the page count considerably
as graphics use much more toner

2. A page with all capital letters will use more toner than a
page with varying amounts of capitals and lower case

3. A bolded font will use more toner than a standard weight font

4. A large point size font will use more toner than a smaller
size font

As you can see, even the type of printing or font can seriously
alter the amount of toner that is used.  AND -- the more toner
that is used to print, the more toner that is deposited into the
spillover tray and the fewer number of copies that a drum is good
for.

Some Other Factors

One point worth mentioning is that some users automatically
assume that the developer or drum needs changing just because
there is something wrong with the printing quality or a spot gets
on the printed page.  The more often a drum or developer is
changed, the more toner that falls out of the tray into the
printer causing less copies to be printed.

Another item to consider is that some users change supplies
because of a printing problem when it is simply the shield plate
(LP 1000) or the transfer or main charger wire that need
cleaning.

How Many Copies Was That Again?

In conclusion, is there any magical way of determining how many
copies a user should be getting out of a toner cartridge or a
developer kit or drum kit?  The answer is YES if you can
absolutely guarantee that each of the printing specifications is
adhered to without fail 100% of the time.  And obviously no one
can do this.  This can only be accomplished in a special
laboratory environment where everything can be controlled.

As a vendor of printing products, we can no more guarantee the
life of a toner cartridge than can the automobile manufacturers
guarantee miles per gallon.  There simply are way too many
driving habits and printing habits to do so.

So why do we bother to publish "life" numbers for our products?
Because it is a finite way to measure and does at least give a
reference point for comparing against different products.  There
is no average customer environment or average customer paper or
average customer printing habit to base these numbers on.  And
remember, the entire printing industry uses a measurement
standard based upon similar laboratory results which gives the
customer something to compare our products to others.

Life Cycle Listings

Cat. #    Description                     Rated life

26-2804   LP 1000                         180,000 copies
                                            Max 3,000 per month
                                            Max 1,000 per day
26-2807   Toner                           2,000 pages
26-2805   Kit A                           20,000 pages per kit
26-2806   Kit B                           10,000 pages per kit

(Based on 5% print using Ricoh PPC 6000/Xerox 4024 paper at 23
degrees C at 60% humidity.)


Cat. #    Description                     Rated life

26-2838   LP 950 Laser Printer            200,000 copies or
                                            5 years (whichever
                                            comes first)
26-2841   Toner                           3,000 pages
26-2842   Drum Cartridge                  50,000 pages
26-2843   Developer Cartridge             25,000 pages


(Based on 4% print using paper specified above at 20-25 degrees C
at 65 plus/minus 5% humidity.)

Note: The LP 950 monitors everything electronically and will tell
the user when to change supplies.
