White spots Roland 308 printing 4/4

Discussion in 'Man Roland Printing Presses' started by Piotr, Mar 24, 2012.

  1. Piotr

    Piotr New Member

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    I have serious problem when printing 4+4 on Roland 308.
    The side printing on the first 4 units looks terrible. I have a lot white spots which made my prints without contrast, and solids ( blue, red ) look grainy. The situation is worst if printing dark colors.
    If I print 4+0 everything is OK even with perfector. It looks like impression cylinders make all white spots. Printing 4+1 I have less spots. I checked all units from 5 to 8 and fund that each cylinder added spots. I observed that picture from the first side transfer to impression cylinder. Cleaning and applying Huber Cylinder Past doesn’t help.
    I use Novavit 918 Bio inks, Alcohol 4%, Fount Printcom S 201 Q, pH 5,5 – 5,8, conductivity 1900
    I attached pictures from microscope x40 and x200
     

    Attached Files:

  2. Meny

    Meny Senior Member

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    sounds like

    you should look for you first side ink on your 2nd side impression cylinders...

    check your jackets on the 5-8 impression cylindersmake sure you are at right pressure

    check your ink tak and good luck
     
  3. Reyltech

    Reyltech Member

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    I have seen this many times with the Miller machines. A Roland 300 series is a Miller TP74 design with all the Roland updates. Many times in this situation it can come down to a few things. Printing Pressure as Meny suggested. the other and is more than likely one of of the issues is the cylinder surfaces. Over time the actual flashchrome texture can get plugged with dried ink and what happens is the surface now becomes smooth and therefore the wetside will tend to pick off on to the cylinder. There is one solution and I only recommend this to be done every once a year. Take some Oven cleaner and clean the textured cylinders thoroughly. Make sure once cleaned you wash them really well with water to neutralize the caustic soda that is in the oven cleaner. Try this and if you still get some of the same effects as indicated, speak to your ink supplier and get a faster setting perfecting ink. Those are my thoughts on a possible solution to your problem.
     
  4. John Van Hoorn

    John Van Hoorn Member

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    Are you printing coated stock?
     
  5. Piotr

    Piotr New Member

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    Yes, mostly on coated stock. The problem concerns only coated stock
     

  6. John Van Hoorn

    John Van Hoorn Member

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    That press was designed to perfect uncoated stock. You can make it better but you will not completely solve the problem.