Side to side color variance

Discussion in 'Heidelberg Printing Presses' started by Steve_M, Dec 14, 2017.

  1. Steve_M

    Steve_M New Member

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    Heidelberg 102, 2002 8 color. The densities across the sheet are all even however the gray balance on the operator side is showing up much more red. We are doing a fingerprint. Any suggestions on why this maybe? We have all new blankets, all the rollers are set correctly. Print order is black, cyan, magenta, yellow.
     
  2. jmt

    jmt Senior Member

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    checked your dot gain maybe more slurring on one side of sheet. we have a same prob with are cyan unit on are cd. more dot gain on ds than os. wish they hurry up and fix it .
     
  3. Steve_M

    Steve_M New Member

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    I wasn't around for the fingerprint, I'm pretty sure that they were checking dot gain throughout the sheet. That's a good question I can ask the other operator that was working on the machine. As far as slurring goes, I don't think so. We had a tech come in the day prior and check all the cam followers and about a month ago checked all the timing of the cylinders.

    One problem I did notice, we run the vario on all the units. When we set the magenta unit with the vario off then turned it on and started running the operator side of the bridge roller. wasn't in contact at all. I'm not sure what is going on with that.
     
  4. Alex63

    Alex63 New Member

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    Hello!! Maybe you have doubling effect on your group no?
     
  5. turbotom1052

    turbotom1052 Senior Member

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    ill go with the dot gain theory as a starting point. It should be noted that the "fingerprint" you did on the press, and the pre press curve adjustments that were made during that fingerprinting, will assume that certain variables are under control. The list of variables are long but it would be fair to point at a few major variables. The first I would suggest you look at would be in the pre press dept. The curves that were determined during the fingerprinting process can drift even before the job gets to the press. You need to be certain that the correct curves are making it to the plate. Ive seen simple things like dirty CTP chemistry cause zonally different sized dots on the plate. Every plate your machine kicks out should include a scale to determine the quality of the CTP performance.
    The next variable to look at would be the paper the jobs being printed on. Believe it or not some paper manufacturers have trouble not only delivering consistency from mill run to mill run, but also problems within a mill run, and to take it one step further inconsistencies from one side of a sheet to another. A problem with uneven coating across a sheet has the potential to cause the very problem you describe.
    Lastly there is excessive dot doin on the press that may come from a few different sources. The mention of a slight doubling or slur by another poster should be looked into. The other issue worthy at a good look would be unstable ink water balance across the sheet. If one side of the press is printing with any instability then an over emulsification of the ink on that side could easily cause the symptoms you describe. As the ink water emulsion becomes waterlogged beyond the emulsion that was present during the fingerprint process things WILL print differently.
    Hope you resolve your issue, and please come back and tell us the outcome.
     
    aqazi81 likes this.
  6. pagey57

    pagey57 New Member

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    could it be the thrush bearings need replacing ? we had that problem
     
  7. KAB

    KAB Member

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    Could always be a thrust bearing check the ductor if its not set correctly it will cause a lot of problems, and try to run a gray field and see if it changes.
     
  8. KAB

    KAB Member

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    To eliminate some possibilities lock off the side guides and ink ducktors and pull a book. KAB/Hasbro/Milton Bradley
     
  9. asem alsafady

    asem alsafady Member

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    Dear Steve,
    I guess that you mean by (bridge roller) the intermediate roller.
    Then you have to readjust it to the dampening form AND the the first inking form roller (the white roller).
    I hope this will help.
    Please let us know.
     

  10. KAB

    KAB Member

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    You have to take it out of Vario first and then set.
     
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