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FM screening lines front to back of plate

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  • FM screening lines front to back of plate

    We have another plant thats required to do some FM printing and they normally don't.

    They are getting fine lines on the plate from front to back. They have tried changing micron size, Resolutions and rotating the file.

    They have also sent the tiff out to be imaged elsewhere on different equipment the lines are still there but are spaced slightly differently.

    They do their screening through nexus, so to me the culprit must be nexus. Never having done FM in nexus I don't know what else to tell them to try beyond what they have done already.

    Any ideas?

  • #2
    Re: FM screening lines front to back of plate

    Hi G_Town


    What plates you using?.........we are currently experiencing this issue's with kodak plates (Ultra), in fact we have had this issue' for 18 months.......have you made sure the plate is been develeped fully?..........have you checked the platesetter...is this laser Ok,.get your supplier to check it out?......... we are on our 3rd laser from kodak!!!

    Hope this makes sense!!!


    Dan

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    • #3
      Re: FM screening lines front to back of plate

      Yea I would think platesetter as well but they sent the files out and imaged them on another brand of setter with similar results.

      I believe they are using kodak golds.

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      • #4
        Re: FM screening lines front to back of plate

        This sounds familiar. See my previous post about lines on the Kodak plates. Suggestions were a "power sweep" of the laser. Prepress solution was to change the chemistry, guess it ate the lines away. This was not FM, but 175lpi. The lines were very fine, and looked like FM. It's been quiet lately.

        John Lind
        Cranberry Township, PA
        724-776-4718

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        • #5
          Re: FM screening lines front to back of plate

          We had a similar issue if I am reading correctly.
          The lines appeared on our plates about 1/8" apart. After several calls to Creo/Kodak, service tech came out and realigned head and corrected laser power. Lines were still apparent but not as bad. He then increased the replenishment rate of the developer in the processor which eliminated the lines. My gues is that the finer screen of stochastic perhaps needs a more potent dev applied. Hope this helps you.

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          • #6
            Re: FM screening lines front to back of plate

            I have been tracking the conductivity of the dev. Originally, we were receiving jugs that would read 88 microsemens. Now its seems like they are only about 80-82 as they come in. Are these older jugs?

            Additionally, we were told that Kodak would be introducing a new PTP and chemistry in the first quarter of 2008. As of yet I have not heard anything. Does anyone have any knowledge of this new plate/chemistry and when it will be available?

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            • #7
              Re: FM screening lines front to back of plate

              for all out there unsure about their lines on plates using Kodak/Creo Thermal heads.

              Laser banding means parallel lines on plates that run around drum. They are 2.24mm apart (224 beamsx10microns). Anything different is not caused by the laser.

              In most cases, it can be corrected remotely or onsite in max 2-3 hours
              For Staccato FM the laser needs to be setup first as there are special settings not used in AM.

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              • #8
                Re: FM screening lines front to back of plate

                We had a very similar problem here. We chased a bazillion different suspects, (laser sweeps, power, focus, chemistry, press blankets, impression pressure, paper...) What it actually turned out to be was the stitching pattern the rip uses to piece together the fm screening patches.
                Kodak reluctantly acknowledged the problem when confronted with one bit tiffs containing the afore mentioned issue.
                They have written a new version of screening using much larger patches. I have yet to see the software but look forward to it''s arrival.
                Hope this helps.

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                • #9
                  Re: FM screening lines front to back of plate

                  Adding some information regarding Michael's post.

                  FM screens are built like a mosaic made of tiles. "Tiling" is a visible artifact usually resulting from uneven ink transfer causing density variation within each Staccato tile which repeats with each neighbouring tile (~ 2mm). The result is a visible crosshatching artifact rather than as lines appearing to go in only one direction (around the drum). If it occurs it usually appears in the black printer. Even though there are huge volumes of presswork done worldwide on a daily basis using Staccato - this issue is quite rare, which is why it is often not immediately recognized. The new version of Staccato that came with Prinergy v4 eliminated the tiling issue, but obviously cannot resolve uneven ink transfer.

                  best, gordo

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