Textures/Lines in screens

Discussion in 'Heidelberg Printing Presses' started by DeluxeBD, Dec 27, 2018.

  1. DeluxeBD

    DeluxeBD Member

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    I have a problem with my SM52. On primarily one of our towers, we're having issues with textures or lines showing up in background screens. The angle of the lines may change, or it may look different on one side of the sheet versus the other. Sometimes it may only show up on just one side, and sometimes it may not show up at all. The picture I'm including shows snips from 3 different jobs. I think we've been able to narrow it down to just the one tower. At a time we thought it was more prevalent when we'd run our Reflex Blue, but we've since had a couple of different greens that produced the same type of effect. We've gone up and down this tower, we've pulled and checked rollers and bearings, made sure we have the correct roller stripe settings. We've also looked for excessive endplay in the rollers to try and find a solution, but we can't seem to find the cause. Has anyone seen or experienced anything like this with their machine. As always, any and all help is greatly appreciated.

    I should also add that we have replaced the blanket and made sure we're packed right while chasing this issue. We're set up identically to the other towers, so it feels like it may be something mechanical happening, but I could be missing something that I should be looking at.
     

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  2. turbotom1052

    turbotom1052 Senior Member

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    Id begin by lifting the ink form rollers off of the plate, one by one, on the suspected printing unit. If that doesn't narrow it down then Id try swapping out the water form from another unit.
     
  3. junker1984

    junker1984 Senior Member

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    Run a breakaway dry solid, in order to determine if it’s in the inker or dampening. Looks like gear chatter to me (not cylinder gears) but do the breakaway first, then if need be, pull the cover and look for wear/shavings in the inker drives.
     
  4. DeluxeBD

    DeluxeBD Member

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    Thanks for the tips fellas... we will try those things next time it rears its ugly head to see if we can narrow it further. And thank you for the clarification (and the analogy ;)) on the term tower... we're more of a "production factory" than tradesmen, so I'm sure there is a lot of incorrect terminology floating around my head and in this building! Dohicky and thingamabob come to mind... :)
     
  5. realaqu

    realaqu Member

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    to me, this looks like a plate problem, did you recently get a new batch of plates?
     
  6. junker1984

    junker1984 Senior Member

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    Isolated to that unit each time?
     
  7. DeluxeBD

    DeluxeBD Member

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    Thanks for the reply, but we know it's not the plates. The pattern is inconsistent and will change through the run... it may come and go, but we know it's not a plate issue, because we'll move it to a different unit with the same plate and the problem goes away. I've asked my operator to try the things that have been suggested when it happens again... he did have a screened image on that tower yesterday afternoon, but it didn't do it on that job. o_O Go figure... It'll be back though. Next week should be slow here, so we should be able to pull the sides and do as suggested.
     
  8. junker1984

    junker1984 Senior Member

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    Be sure to first pull a dry, breakaway solid to see if it’s coming from the inker before you start removing covers. Also, you mentioned going through the rollers, does that include the damps? Is the chatter across the whole image area?
     
  9. DeluxeBD

    DeluxeBD Member

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    Yep, will do. Yes, we've had all the rollers out to check the bearings, etc. and went through and restriped the inkers and the damps. These forms are ran 2up across a 17" sheet, sometimes the lines, or movement, or texture (It's not always the same) will be across the entire image, sometimes it will only be on one side and the other will look fine, and other times it might only show in an area on the sheet, and it will come and go. Startup and run several hundred sheets fine and then it might appear for a while then go away again or it may not. The thing that's difficult for me to understand is the consistency of it... if we're calling them lines, the lines that appear aren't necessarily parallel to the sheet.... sometimes they might angle up from L to R, and sometimes they may angle down. I have a sample in my office where on one side of the sheet the lines angle downward, but on the other side, it's not really lines, but there is a movement in the screen that is angled upward. It's strange, but we'll do the things that have been suggested and try to sort it out.
     
  10. asem alsafady

    asem alsafady Member

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    Hello Deluxe,
    Can you send clearer pictures please.
    Then we might have a solution.
    Regards.
     

  11. NotAGooner

    NotAGooner Senior Member

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    Could be bad impression grippers on that unit or bad cam / follower, try heavier stock to see if it disappears?
     
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