G7 press calibration, best press conditions or average?
G7 press calibration, best press conditions or average?
- Subject: G7 press calibration, best press conditions or average?
- From: Paul Foerts <email@hidden>
- Date: Fri, 31 Oct 2008 00:57:47 +0100
On Thu, 30 Oct 2008 09:00:03 -0500 Steve Miller <email@hidden>
wrote:
> We have been using the G7 method of press calibration for two years. It has
> helped us tremendously. Each time we calibrate, (we have several presses) I
> have a discussion with the press room regarding the condition of the press.
> I have always recommended that the press be in the best printing state that
> the press can possibly be in. The press room has the opinion that the press
> should be in an average state. Meaning that after press maintenance has been
> conducted, the press should be allowed to run halfway through the time
> period before the next scheduled press maintenance is performed. Then
> perform a G7 calibration. That way they get an "average of press
> performance".
> I'm well aware of the Press Operators guide to color and G7 and the press
> check list that goes with it. I've shared these documents with the press
> room.
> Do any of you have an opinion on when the calibration should be done? Also,
> if it is best to calibrate soon after maintenance when the press is printing
> at it's best, how can I explain to the press room that this is the best
> press condition to calibrate using the G7 method?
>
> Thanks,
> Steve
Steve,
Well... (sorry for the tone, I couldn't resist):
A conventional offset printing press cannot be "calibrated". Presses are
"adjusted" by press operators.
Without "adjusting" operators, there is no "definable" printing condition
possible.
You may use the G7 "methodology" to aim at an ISO standard printing
condition. This methodology however cannot make a new press from an old one.
You can compensate for TVI but you cannot eliminate process variations.
Press maintenance is a basic part of process control.
Press manufacturers have advanced tools for evaluating the accuracy of their
presses. GATF has vernier tools available for DIY analysis.
If the deviations in color to color register surpass a certain limit, you
(the press of course) need "maintenance".
When it is no longer possible to aim at your standard printing condition you
need to find the cause for this failure. Why would you use the G7
methodology for this?
The presses should always be kept in their best printing state. The standard
printing condition may be "average". This way all presses may be able to
satisfy.
I suppose this is what the press room meant.
Paul
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden