About "average" press condition and calibration
About "average" press condition and calibration
- Subject: About "average" press condition and calibration
- From: Roger Breton <email@hidden>
- Date: Sun, 02 Nov 2008 09:29:10 -0500
This is another ongoing argument in the trade.
For my part, I favor starting with new blankets, new, fresh fountain
solution, fresh everything. Squeeze needs to be re-adjusted between the form
rollers and every simple adjustments checked. I know some tradesman advocate
calibrating in an "average" condition but that, to me is not the true spirit
of calibration which is, as was repeated many times on this List by many
contributors, the idea of putting the device in a *known* condition. As Mike
said, when the ***it hits the fan, it's always possible to fall back on some
known state and ask the question, what is it that changed? Otherwise, it's
not possible to know what changed. Because there are no documented reference
point.
The one problem I keep seeing on presses of all kind is the lack of controls
on the all too critical ink/water balance, as part of press calibration.
There exists some ink film thickness gauge that can be used, when the press
is stopped, to sample the ink film on the oscillator. But that's hardly
"online". The problem is that every press operator will set the dampener
system according to their judgement and experience (and taste too). Most
operators I know will take the time to walk up to the units and observe the
plates in rotation, as the press runs, and if they see a satiny look, when
looking at the press from an oblique angle, they'll know they don't have too
much water on the blanket. Some will go as far as making the press scum and
then raise the water back up until it does not scum anymore. That's another
trick. But that's hardly scientific. And to think that newer presses now
have these auto plate loading system, that completely hide the plates as the
press runs, some other heuristics has to be found, obviously. I don't know
how these pressmen do but this ink/water balance issue, when everything else
is in control, can easily derail any characterization or calibration
efforts. Let's not forget that some paper absorb more than others and need
more water than others. The trend with precipitated calcium carbonate
coating being used more and more in manufacturing to cut costs down is
another nice wrench thrown into the mix. I wish there was some way of truly
monitoring the ink film characteristics as the press is running. Gosh --
even ink suppliers are dumbfound by this issue : no one has the definitive
answer. And say that wew presses keep coming out with the same illogical
ink/water designs, it's like no one is learning? Hello? We have PDF, ICC
profiles, Device Link Profiles, GMG RIPs, the G7 method, the iSis, wide
gamut LED monitors but we're still in the stone age of controlling something
as basic as ink/water balance?
I think I'll have that second cup of coffee now...
Roger
> If the press is in its best condition with new blankets you have a
> reference baseline to return to when things go awry. You can't say
> the same of "average" condition.
>
> Mike Strickler
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