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Date: | Mon, 30 Sep 1996 18:51:59 -0700 |
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Based on recent tests and discussions with International Light I can say that the use of any light meter like the 1441 and its probe is not relevent to the performance of dry film. I had an old 400 watt source and a 1000 watt source. The 400 watt source gave me 26 mj and the 1000 watt source gave me 90 mj. Interesting thing was that both sources gave me a step of 9+ on the 21 step scale. I called IL and they cleared it up for me that the Step Scale is the only real measure that is truelly accurate for testing dry film exposures and also performance. The IL input was that to test a specific unit and then zero in that unit with a step scale will usually work to then come back and check just that unit with the meter is OK and meaningful. But do not assume the mj reading has any relevence to performance of dry film because it responds to a wide range of light that your probe can not accuratly measure the true volume of light. Call IL and talk to their engineers. They are great and very helpfull on this subject.
Kerry Grimes
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From: [log in to unmask][SMTP:[log in to unmask]]
Sent: Monday, September 30, 1996 4:41 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re[2]: FAB: SPC of printer
Recommend using an IL 1441 - System Radiometer for measuring light
intensity in place of a Stouffer step. One procedure is to use 100
mj/cm as a constant and use the average of top and bottom lamp
measurements as the SPC data point.
______________________________ Reply Separator _________________________________
Subject: Re: FAB: SPC of printer
Author: [log in to unmask] at CCGATE
Date: 9/26/96 2:35 PM
In your message dated Thursday 26, September 1996 you wrote :
> TechNetters, here is another question about SPC.
>
> Is anyone using SPC at the board image printing operation? Our people
> here have been, at times and in an undisciplined way, been taking energy
> data from the printer. The gauge is put at 9 points in a grid and energy
> delivered thus measured. (These 9 measurements are made at approximately
> the same time, at the start of a shift, say.) To me, this approach
> seems to lend itself to SPC. Presumably, the measurements would be done
> on a regular schedule.
>
> Anyone care to comment or correspond? Lou Hart Quality Assurance
> Compunetics 412-858-6117
Hello Lou
This check does not need to be done very often. Once the characteristics of the
unit have been plotted and the step wedge difference in the corners and the
centre of the exposure area have been established, they are not going to change
significantly in a short time. You might want to recheck every 3 months but we
never find any change in the distribution.
All that needs to be monitored daily is the exposure step achieved for the light
units set, and the time it takes to achieve those light units. Time will
increase as the lamps age and although the step may still be within limits, the
image quality will deteriorate as the time increases.
Daily plot the exposure step, and the time in seconds. Keep the step within
recommended limits, and set a maximum time at which to change the lamp(s). This
should be not more than 50% longer than new lamps ideally, but you could stretch
them for longer depending on the type of work you are doing.
Paul Gould
EMail [log in to unmask]
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