A problem in the second cycle of entering the paper for printing

Discussion in 'Heidelberg Printing Presses' started by ali 120, Nov 21, 2023.

  1. ali 120

    ali 120 Member

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    There is a problem that has appeared in the gto 52 dds machine
    When the paper enters the machine for printing the first time, the paper comes out of the machine in even colors and there is no problem.
    But when the same paper enters a second cycle in the machine with the same colors and the same product, a phenomenon occurs that the paper comes out of the second cycle with an uneven color.
    It has high and low colors
    The blanket has been changed
    The ink quality has been changed
    But there is the same problem
    There is a picture for clarification
    You will find that the colors are irregular after the second cycle
    https://www.raed.net/thumb?id=494215
    https://www.raed.net/thumb?id=494218
    https://www.raed.net/thumb?id=494216
    https://www.raed.net/thumb?id=494219
     
  2. Raf77

    Raf77 Senior Member

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    You have registration issue pal.
     
  3. ali 120

    ali 120 Member

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    Why do you mean there is a problem with registration?
    Knowing that the first cycle of color is excellent and there is nothing wrong with it
    The problem is in the second cycle
     
  4. Raf77

    Raf77 Senior Member

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    On the 1st pass colour will be the same regardless of registration. On 2nd pas if it's not registering correctly (dot to dot) there will be colour differences. It's like you'd print twice as much dots as at the first pass.
     
  5. ali 120

    ali 120 Member

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    What do you think is the solution
    Do you mean by registering to adjust the ink cylinders on the board?

    Or by recording, you mean adjusting the pad cylinder to the blanket cylinder
     
  6. Raf77

    Raf77 Senior Member

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    I don't understand what do you mean.
    Firstly check front lays and side lay - if paper is laying correctly on them.
    Then check the cam follower on impression cylinder.
     
  7. ali 120

    ali 120 Member

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    Is it possible to have pictures showing the places you want me to check?
     
  8. SAICPRINT

    SAICPRINT Member

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    It looks like from the photo you posted that your color is not consistent form sheet to sheet.
    The density in the magenta is stronger in some sheets then others, for example.
    I have had this same problem lately, and have tried different inks but no luck. My ink rollers looks like
    they need replacing so that might be the culprit, I'll try that next. On a side note the registration was correct.
    Have you tried adjusting the fountain solution?
    I have reposted the photo of your sheets for clarification.
     

    Attached Files:

  9. Raf77

    Raf77 Senior Member

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    Not at the moment pal. It's really simple machine - just check step by step every stage of sheet travel through the machine
     
  10. Raf77

    Raf77 Senior Member

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    You're talking about different problem
     
  11. ali 120

    ali 120 Member

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    What do you mean

    Have you tried adjusting the fountain solution?
     
  12. ali 120

    ali 120 Member

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    What do you mean
    Then check the cam follower on impression cylinder.
     
  13. asem alsafady

    asem alsafady Senior Member

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    Dear Ali,
    I don't understand why you want to print the same sheets with the same colors again.
    It's impossible to print dot over dot typically.
     
  14. ali 120

    ali 120 Member

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    Sometimes the paper needs to go through a second round
    It is assumed that when the paper enters a second cycle, it will have a fixed degree of color, but what happens otherwise is that one sheet of paper is a dark color and another sheet is then a lighter color.
     
  15. Raf77

    Raf77 Senior Member

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    But why you print one colour twice instead of changing the artwork???
    It's ok to do double hit when printing solids, but not screens.
     
    Raituss likes this.
  16. Raf77

    Raf77 Senior Member

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    And that 8s because of bad registration. You're doubling the amount of dots - that's why it's darker
     
  17. ali 120

    ali 120 Member

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    As a reminder, not all paper is dark in color, and also the dark color appears in the last quarter of the top of the paper.
    And how to adjust the intended recording
    Is it adjusting the ink cylinders or adjusting the printing cylinder with the blanket cylinder?
     
  18. Raf77

    Raf77 Senior Member

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    Check:
    - if plate thickness is correct
    - if blanket plus packings thickness is correct (as I can remember is 3mm in GTO)
    Even if your registration is correct (but I don't think so) then if your blanket is overpacked or if you print at too much impression your paper may be stretched. Just check plate and blanket - change it to 3 mm if needed and give it a try
     
  19. ali 120

    ali 120 Member

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    I checked the blanket and it is indeed 3mm
     

  20. Jack liston

    Jack liston Senior Member

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    Are you using the the correct grain for the paper is the paper crap
     
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