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Thread: Random image shifting with mixed media

  1. #1
    Join Date
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    Default Random image shifting with mixed media

    Hi All,
    Hopefully someone has solved this problem already! I am running on a KM 1070 using CWS 5.8.
    Simple job = approx 30 pages duplexed onto 8.5 x 11 sheets. Mixed media is making pages 1-2 duplex from same stock (92-105 gsm range) from a different tray. So essentially a cover.
    The "guts" run and align perfectly, but no matter what tray I use, no matter how I duplex it (top or R-L), I get random shifts of up to 10 mm left on the cover page only. About 30% of the copies are aligned properly. I can make this work by running 8.5 x 11S, but I don't want to do that due to bad paper curl.
    Stranger still, during testing I ran 2 copies of a book: Copy 1 is perfect, Copy 2 shifted the front (?!?), again both guts are aligned perfectly.
    Anyone had this before?
    TIA
    Michael

  2. #2
    Join Date
    Feb 2013
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    Default [solved]

    ...It's nice to say "Solved". It happens all too rarely.
    So, it turned out the culprit was that I was printing onto preprinted stock that had a phrase printed on it. As it was setup, this stock was set face down (Preprinted side down) and when it ran through the machine, it would trip the "centering sensor" and cause the random image shifts I had experienced. I was curious because I saw no evidence of this shifting with any other job.
    Turning face up, meaning the preprinted side is UP and not going to face the sensor, my Tech and I were able to reliably prove this theory by running the stock in certain ways and watching this shift happen on only the pages face down with the preprint in the way.
    Hope that helps someone!
    Cheers!

  3. #3
    adam1991 is offline Fiery Forum Expert Contributor adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful
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    Default

    yeah, so the shifts were not, in fact, random.

    That's quite interesting. Thanks for the reveal.

  4. #4
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    Default

    Strictly speaking Adam1991, they actually were random - I noticed that the centering sensor sometimes nailed the dimensions correctly and the page would print fine, but more often than not it wouldn't. It was a real tossup whether this was a mechanical / RIP / InDesign flaw and this was hard to find, but with some help we tracked it down.
    So, while the experiment would yield predictable results, the copier, it seemed, was doing it's resolute best to center an image with only about 30% success. We surmised the preprinted image was barely clipping the sensor, enough to trip it, but not all the time.

  5. #5
    adam1991 is offline Fiery Forum Expert Contributor adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful adam1991 has proven very helpful
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    Ah.

    I will say, this is virtually 100% guaranteed NOT to be a RIP issue. Ever. There are no conditions where the Fiery would be randomly shifting the image.

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