Spray powder wearing plates on 2nd pass

Discussion in 'DI Presses' started by Britishprinter, Jan 2, 2013.

  1. Britishprinter

    Britishprinter Member

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    Hi everyone, new to printing on a Heidelberg quickmaster di classic.
    I'm having problems when printing on a 100 gsm bond , side one runs great with spraying set on 2, with a silicone coated spray powder.
    When I print the reverse the spray powder transfers from the paper to the blanket and then the plate, wearing it out causing light spots over the entire image.
    I can't run the spray any lighter as it starts to set off.
    Anyone experienced the same problems and any solutions would be greatly received.
    Forgot to say im using Toyo inks.

    Thanks again for reading.
     
  2. Bill Borcicky

    Bill Borcicky Senior Member

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    is this only on longer runs or will it also happen on short runs? I also have had powder build-up at times, I had noticed my powder get clogged at the end of the lines which allowed powder to spray one direction on one side. Powder would build-up and create a problem such as that which you have. I had to wash off the blankets by hand to clear the powder until I had time to work on the powder unit. I had tried the automatic blanket wash but found that I had to clean that as well after a few runs. I now run ( AS-160 ) powder from Nikkalyco (Nikka ) which gives me less problems.
     
  3. Britishprinter

    Britishprinter Member

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    Hi Bill,
    Thanks for your reply. In answer to your question, it's usually on a run of about 5000 but have to wash the 1st blanket by hand every 1000 sheets when backing up.
    I understand that there are two types of spray, coated and uncoated . Was wondering if this has any bearing or the micron size ?
    As I said earlier have been an litho offset printer for many years but a learner on waterless plates and DI machines.
    Thanks again for your feedback.
     
  4. Bill Borcicky

    Bill Borcicky Senior Member

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    as for the spray powder, I have always used one type for all, if it works on coated stock it should work on uncoated as well { my opinion } I have never changed, one stock to another and have no problems. My rule of thumb : if you can put the powder in a cup and swirl the cup around a little, if the powder moves like a liquid swirling, the powder should work fine. Fine micron works better with DI presses { my opinion }
    One thing to remember, when adjusting to the DI machines, plates don't last as long as one may think they should. I have found that they may last in the area of 20,000 impressions on average. if you find yourself in the range of 15,000 - up, I believe that should be acceptable to cover costs.
     
  5. Paul Cavanaugh

    Paul Cavanaugh Senior Member

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    Powder in the 23 micron range helps dramatically. The Nikka powder worked well in most instances. As always, run the least amount of powder you can.
     
  6. Britishprinter

    Britishprinter Member

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    Thanks for that Paul,
    Will try and find out what micron I'm using at the moment. It just says fine spray on the bag. I was just wondering of the silicone coating on the starch spray powder was too hard for the plates as opposed to just starch on its own. I realise with no water involved in the process it wouldn't disappear but thought that the moisture in the air might help soften on 2nd pass.(just a theory?)
    Thanks again for your advice, need all I can get at the moment.
     
  7. Paul Cavanaugh

    Paul Cavanaugh Senior Member

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    If you have enough moisture in the air to disolve a starch based powder, I am guessing you are going to start having rust problems soon... :)
     
  8. Bill Borcicky

    Bill Borcicky Senior Member

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    I would be thinking that with the silicone, it would create a problem by sticking to the plate ,as would the fine threads of silicone do when you burn a plate and the plate is not cleaned properly. { just a thaught , though I had never really used silicone powder }
     

  9. ryobidave

    ryobidave Member

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