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With all the high speeds and productivity
needed in today's sheetfed market, How
does the printer keep it all together?
20 or 30 years ago most of the process
was hand driven in other words all press
operations were completed by hand. If
you needed to adjust ink, you did it by
"tweaking" the "ink keys" at the ink fountain
which meant climbing up to the ink system
on the press. Most of the rollers also
needed to be engaged by hand. Ink levels
and print quality was left to the eye
of the press operator which of course
varied over the course of the day. When
a new job came to press, the press operators
had to "eyeball" the plate and make a
guesstimate as to where the ink keys and
fountain should be set - a trial and error
method. Today, however, is much different
as automation and computerization has
set in. Today's modern sheeted-presses
are fully automated with internal computers
do assist the press operator. Presses
can come equipped with a "plate scanner"
and computer consoles to do many of the
tasks the press operator did by hand years
ago.
Today when the offset plate comes to the
press, the press operator can scan the
plate on a "plate scanner" (if equipped).
The image densities are read across the
individual plate and the fed into the
press console which can then preset the
ink keys and the ink fountain (total ink
flow). The operator can scan the black
offset plate, for example, via the press
computer the black ink unit would be preadjusted
based on the readings taken from the plate
scanner. The same would be done for all
the additional plate colors such as cyan,
magenta, yellow and any other special
colors.
Plates
today can be automatically "hung" or mounted
as well as be removed without operator
interaction. Cleaning of the blankets
today also is fully automatic. Once the
plates are mounted make-ready begins.
While the plate scanner will be close
in color and density, the operator usually
has to make some small adjustments on
color and registration. Unlike in years
past, however, the operator can do this
electronically through the press console.
With a image scanner attached to the press
(closed loop) the press sheet can be scanned
using color bars. This device measures
ink density and relates it to ink film
thickness. The operator can read the results
via a computer screen. By electronically
activating the ink keys and fountain via
the press console adjustments are made
quickly and easily compared to years past.
Once the customer or press operator has
approved the color the press operator
can "lock" the values into the computer.
During the press run the operator will
scan sheets every so often on the scanner
to measure color. If a color starts to
shift out of tolerence, the scanner will
display that information and the operator
can "send" the data over to the press
computer which will automaticity adjust
the proper ink unit to bring the density
levels back in customer tolerance. Some
modern presses today even have the color
system "closed looped" fully so small
adjustments are being made continuously.
You can do the same with an off-line scanner
or hand held scanner, however, the press
operator will make a judgement call based
on their experience on changing the ink
level (via the press console). What has
this done? Well, it has speeded up make-ready
time by as much as 85% which in turn reduced
cost and increases productivity.
With any manufacturing process, and
printing is a manufacturing process, productivity
is a must!
This
unit is programmable from the press console.
A cloth material is installed in the unit.
As it washes, with press solvent also
being applied, the cloth material will
"wipe" the debris and solvent away. At
the conclusion of each wash the cloth
will advance. After a while the cloth
unit needs to be replaced with a new cloth
unit.
Important
Properties
- Paper
Consistency
- flat
and dimensionally stable
- Good
surface strength
- Surface
cleanliness
- Good
slitting/cutting - clean edges
- Accurate
and square cut
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