Display article   Subject:  All About Ribbons
   04/30/97   19:17:59


ALL ABOUT RIBBONS

The number of characters that a particular printer will print
using a black printer ribbon is a subject that has `no good
answer.'  It has also been a subject of discussion among
customers and manufacturers since the dawning of personal dot
matrix printers and even a subject of discussion in mainframe
computers for years and years.

It is as hard to define as how many miles a particular car will
get per gallon of gas.  The number of variables involved is
amazing -- all which can drastically alter the number of
characters significantly up or down.

This `magic number of characters designation' can be affected by
such things as:

1. Quality of paper printed on -- since ink is a liquid of sorts,
the more porous the paper, the more ink is absorbed into the
paper.

2. Print mode of the printer -- graphics characters take much
more ink than do letter quality characters, which in turn take
more ink than draft characters.  And even the pitch of the
printing can alter the number of characters.

3. Temperature of the ribbon -- there are obviously limits to the
highs and lows, but a cold ribbon will print fewer characters
because the ink will not `flow' as smoothly.

4. Method of printing -- printing for continuous periods will
result in fewer characters than printing one page at a time, or
several smaller print jobs.  Once again, since ink is a liquid of
sorts, it migrates from all parts of the fabric used in the
ribbon.  When printing continuously, the ink doesn't have time to
migrate from the outer edges into the center of the ribbon.  It's
kind of like when it rains on the highway and a long line of cars
drives over the wet spot continuously -- the road where the tires
meets the pavement dries more quickly.

5. Also, the acceptable darkness of the characters when someone
decides that the ribbon is `used up' varies greatly from person
to person.  This one factor can change the count up to 50%.

6. Type of ink used -- the ink used in the ribbon also
contributes to how many characters can be printed.  Simplifying
this a bit -- some inks are designed for continuous printing and
some are designed for short print projects.  Some are designed to
last for months and months in an unused state, and others are
designed to be used immediately.

If you can imagine the different types of customers that purchase
our printers, it would be impossible for Radio Shack to
specialize in one kind of printing application.  Some of our
users print literally hundreds of pages at one print session, and
others print only one page a month.

You can see that ribbons must be designed to offer the most
flexibility -- the ink must last from hours to basically a year
or two without completely drying out because of non-use.  At
Radio Shack we have tried to give our users the best possible
solution to fit all situations evenly.


Other Items of Interest

Some ribbons are wider than others, like the DMP 133/134 ribbon
versus the DMP 300.  This wider type of ribbon actually has a
`mobius twist' and actually passes through the printhead upside
down on alternate passes.  In addition, this `wideness' is
intentionally designed into this printer to allow the ribbon to
absorb lots of ink (remember that ink migrates).  Since the
DMP 130 series printer is typically used for very small print
jobs, the ink has plenty of time to migrate from the outer edges
of the ribbon.

The DMP 240 printer is designed for a specific purpose -- that is
to have color capability.  This, then, precludes the same design
on the ribbon as with the DMP 133.  (A color ribbon cannot have a
mobius twist or the colors would reverse!)

Color ribbons typically have shorter life spans than black
ribbons.  In fact, color ribbons do not have a specific character
life associated with them because they are typically used in
printing graphics which tend to use much more ink than just plain
text.  In addition, color inks tend to have more `solids' in
them, reducing the printing life.

Ribbons like those used on our 24-wire printers are typically
rated at 2 million draft characters.  And if you think about it,
if that character number was applied to a typewriter ribbon and a
person typing at 60 characters per minute, it would yield over
111 hours of typing.  Applied to the number of pages -- it would
yield about 1,000 pages of draft text at a cost of about one
penny per page, compared to current costs of about 3-4 pennies
per page from a laser printer.  All in all, the costs are
reasonable.


Printer Ribbon Suggestions

Use letter quality mode only when absolutely necessary.

Keep older ribbons to print draft documents where darkness and
quality are not required, and print all draft documents in draft
mode.

Keep a separate `letter quality' ribbon that you pop in when
printing final versions of important documents.  Then when this
ribbon becomes too light in letter quality mode, change it to a
`draft mode' ribbon.

Don't keep large numbers of extra ribbons on hand; use the local
Radio Shack store as a stocking location where the turnover of
ribbons is much greater.  This will insure the `freshest' ribbons
when you purchase.  The shelf life of a ribbon is approximately
one year, and performance will start to deteriorate after this
period.

Radio Shack continues to look at this area of printer ribbons.
We are constantly trying to improve performance and still
maintain that delicate balance for the myriad of printing
requirements that exist with purchases of dot matrix printers.
There is no one single answer for everyone.  Unfortunately, with
the current situation in the oil industry (petroleum is used in
the ink and plastic) finding an economical way to increase print
life is becoming harder and harder.

Remember, "old ribbons never die, they just draft away."
