Color doesn't hold on edges.

Discussion in 'Komori Printing Presses' started by Milehighking303, Jan 22, 2020.

  1. Milehighking303

    Milehighking303 New Member

    Joined:
    Jan 2020
    Messages:
    1
    Location:
    Denver
    Have problems with color dropping on 1 side. If I run a small book no problem. Its when I run a larger book it dips. If I rise my keys same thing happens. I replaced all rollers. Still same problem. I'm out of ideas. I don't see any excess water on edge . I'm out of ideas. Thanks ahead of time.
     
  2. alibryan

    alibryan Senior Member

    Joined:
    May 2014
    Messages:
    217
    Location:
    Somewhere
    It’s helpful to know first, what press you’re using? And even though by itself it may not solve your problem, it may help to try to remember that there’s usually only two things present in the printing process; ink, and water. There’s probably either going to be not enough of one, or too much of the other.
     
  3. turbotom1052

    turbotom1052 Senior Member

    Joined:
    Oct 2008
    Messages:
    1,044
    Location:
    Vermont
    "Seeing" excess water on the edges, as the press is running, is becoming more and more difficult when you consider all the safety guards, and the high speeds modern presses run these days. I think a better indicator would be to look for a scum line at the very gripper of the plate, where the plate cylinder bevels from the clamps to the actual cylinder. If you notice an even scum line that continues to the very edges of the plate then id say you've got good water control right to the edges. If you find that the scum line becomes washed out the last couple of inches of plate width then id be looking at a skew adjustment to dampener, and if no such adjustment exists on your press, then perhaps you need to look at crown in the pan roller. You could also use the dampening systems air curtain bars if so equipped to control the edges.
     
  4. alibryan

    alibryan Senior Member

    Joined:
    May 2014
    Messages:
    217
    Location:
    Somewhere
    I’m curious what your thoughts might be on skewing the pan roller, and/or having a crowned dampening roller already in the dampening system. I know what the theory behind it is and what it’s designed to do, but I think that like so many other things in the printing process, people seem to have different thoughts and ideas about what it actually does.

    I’m really not wanting to try and debate it in here, I’m just curious what you think. I also wanted to say that even when people agree or disagree on something (myself included), it doesn’t always necessarily make it a fact.
     
  5. turbotom1052

    turbotom1052 Senior Member

    Joined:
    Oct 2008
    Messages:
    1,044
    Location:
    Vermont
    As mentioned before, it is my feeling that between all the safety guards, and the high press speeds of modern presses, the days of a visual inspection of a printing plate while running is no longer possible. That being said all that your really left with to determine if your dampening settings are correct would be to look at the plates gripper when stopped. This is why Im a firm believer in not missing a single opportunity to do just that. If im stopping the press to wipe off a stubborn hickey, im checking that unit for a scum line. If im stopping the press to check roller settings during a run, Im checking the scum line. Any time, for whatever reason, im going into a printing unit im not passing up the chance to check for a scum line.
    The OP mentioned washing out on the edges of the printed image after a bit of running. I believe that Komori presses like many other manufacturers allow for skew adjustment in order to lay an even film of fountain solution. This setting tends to be a very slight adjustment from one extreme to another. Being a very slight adjustment tells me that there will be no really glaring effect over the short term. Its over the course of running for a bit, that an excessive water feed on the edges would have a tendency to creep up and wash out the images on the edges. Were all familiar with the way that a pressman can chase color because of an uneven water film. If it turns out that the regular visual inspection of the plates gripper shows the plate washing out on the edges, and tightening up on the metering roller is doing nothing but drying up the middle, then I would say its time to put the pan roller more parallel to the metering roller and perhaps speeding the dampener up a little if required.
     
    Last edited: Feb 2, 2020
  6. alibryan

    alibryan Senior Member

    Joined:
    May 2014
    Messages:
    217
    Location:
    Somewhere
    Thanks
     
    Last edited: Feb 5, 2020

  7. Yorkshire Gripper

    Yorkshire Gripper Senior Member

    Joined:
    May 2012
    Messages:
    79
    Location:
    UK
    I go around fixing these problems all the time. Usually comes down to settings. People tell me that the settings are correct 95 percent of the time they aren’t. If it’s ok on one side but not the other it’s settings
     
Loading...