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Flexo distortion - out of register when combined with rotary screen?

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  • Flexo distortion - out of register when combined with rotary screen?

    Hello!

    Our narrow-web flexo press (a Gallus ECS 340) has the capability to print rotary screen in combination with flexo. Recently we've noticed on certain jobs that the screen printing is out of register with the flexo printing, as if the distortion is off. Specifically, the white screen ink doesn't line up directly behind the flexo ink--it appears to be off every other label.

    We've been using the same flexo distortion numbers for years (appears to be industry standard, per a Google search), but now we've actually developed a new flexo distortion chart specifically for this press (by trial and error on this one label project).

    Example:
    16.5" (132 tooth) cylinder, .067 DuPont plates
    Old distortion: 97.636%
    Old distorted length: 16.11"
    New distortion: 97.70%
    New distorted length: 16.12"

    Our screen material is imaged from a piece of film, which is imaged on a CDI Spark 2530. No distortion is applied to the screen file.

    Now we're finding that our revised formula isn't working--the registration is still bad on the same job, from one repeat to the next (this is an 8.25" repeat, two images around the cylinder).

    Does this sound familiar to anyone? I've never encountered an issue like this in 19 years of flexo printing (eight of it combo printing), where a new distortion formula was needed.

    Gallus provided us with a snippet of a manual explaining distortion and methods for adjusting it (attached)--it seems to suggest that revised distortions are sometimes required for combo printing (flexo & screen on the same item). However, since our newly-extrapolated formula isn't doing the trick, I'm on the hunt for any other potential causes.

    Any feedback is greatly appreciated--thanks!
    Attached Files

  • #2
    Bumping--any thoughts? Thanks in advance!

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    • #3
      Well that's just down right weird.

      Are you 100% certain your plate material or plate tape has not changed? Even if you are ordering the same stuff from the same supplier, some stock might have got mislabelled or specifications might have been altered?

      Comment


      • #4
        No changes to plate material or tape to my knowledge, and I work in the plate & mounting areas as well as in graphics, so I've dealt with the plating & mounting. We've had the press for about a year now, brand new when we purchased it.

        It seems to only be noticeable with combo printing (flexo/rotary screen), and particularly with one project where there's a small ® registration mark in flexo black, backed up by a halo of screen white. It's a 16.5" cylinder, 2 around (so a repeat of 8.25"), and the white behind the ® shifts position from one repeat to the next.

        Update: late last week, we tried a new distortion number (we run this same project probably twice a month), and it seemed to work best. It's right in between the numbers for our first & second revisions.

        Our policy has been to create a whole new distortion chart based on the results from this project, and just use it on this one press (our other presses don't run the same plates and/or stock widths).

        Comment


        • #5
          Originally posted by prepress labels View Post
          No changes to plate material or tape to my knowledge, and I work in the plate & mounting areas as well as in graphics, so I've dealt with the plating & mounting. We've had the press for about a year now, brand new when we purchased it.

          It seems to only be noticeable with combo printing (flexo/rotary screen), and particularly with one project where there's a small ® registration mark in flexo black, backed up by a halo of screen white. It's a 16.5" cylinder, 2 around (so a repeat of 8.25"), and the white behind the ® shifts position from one repeat to the next.

          Update: late last week, we tried a new distortion number (we run this same project probably twice a month), and it seemed to work best. It's right in between the numbers for our first & second revisions.

          Our policy has been to create a whole new distortion chart based on the results from this project, and just use it on this one press (our other presses don't run the same plates and/or stock widths).
          Using the same Press as you are with combo printing and we use the distortion K-factor of 0.37 which would be 97.76% for 132T. PM me your email address and I can send you our distortion chart that we use.

          Comment


          • #6
            Hello

            I have varnish machine distortion is a same ?

            Thank's

            Comment


            • #7
              Originally posted by StillWaiting View Post

              Using the same Press as you are with combo printing and we use the distortion K-factor of 0.37 which would be 97.76% for 132T. PM me your email address and I can send you our distortion chart that we use.
              Got it--thanks a bunch for the info!

              Comment

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