Powder make my printed sheet rough

Discussion in 'Heidelberg Printing Presses' started by Daniel AK, Apr 13, 2017.

  1. Daniel AK

    Daniel AK New Member

    Joined:
    Apr 2017
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    Location:
    Indonesia
    Hai,
    I'm Daniel from Indonesia. This is my first time i write a thread.
    I have a problem with powder used. I used mix 10-30 micron coated powder.
    My printed sheet is feel rough when it dry. I try to clean using dust remover machine, but the result is still rough.
    Anybody can advise something to me ?
    Thank you.
     
  2. turbotom1052

    turbotom1052 Senior Member

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    retired to panama
    Instead of mixing 1o micron and 30 micron powder you may want to stick with a single smaller size. For most commercial applications you should be able to get by with something in the 25 micron range. You may want to gradually explore running less. Is your press equipped with an aqueous coater? If so running coating should allow you to lower your powder usage. In addition I would be looking at your total ink densities, not exceeding about 280 percent. If you keep the TID at 280% or under you will lessen the need for excessive powdering of the sheet. You may also lessen the amount of powder needed by racking the printed job as it delivers.
    I know my suggestions do nothing to fix the current overuse of powder, but they are offered to prevent future problems.
     
  3. Daniel AK

    Daniel AK New Member

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    Apr 2017
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    Location:
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    Hi Turbotom1052,
    I print Cigarette box, use carton paper 210-250 gsm. The most ink is Black with density 2,30-2,50 (i print with 2 printing unit).
    I test the thickness of the ink is around 15-20 micron (using thickness gauge).
    I heard from my friend, if your powder is to small (less the the tickness of the ink), the powder will drawn in the ink and can't pill off using dust remover or other. Is it true ? He suggest me using 45 micron powder, but i worry it will be more rough than before.
     
  4. turbotom1052

    turbotom1052 Senior Member

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    I hadn't realized that you were a packaging printer. Being that you are, I would say that a 30 micron powder is not excessive. As a matter of fact you might do as your friend suggests and run a larger size. Perhaps you need to test the limits of your powdering by cutting down the dial a little at a time until you reach the point where you see setoff. One you begin to see a bit of offsetting then you can increase it a bit.
    Also the fact that you are doing multiple passes on a 2 color press doesn't help matters. Have you experimented with running a non coated powder? Is your press equipped with an infrared dryer, and are you using it properly? Last but not least you might want to explore the strength of your inks. The easiest way for SOME ink suppliers to cut costs would be for a reduction in pigment. The pigment in an ink is the most costly component. By cutting down on the inks pigment the ink company saves money on raw materials, and then winds up making money by selling you more weak ink. These weakly pigmented inks will need to be run at a thicker film ,to arrive at the same densities as a stronger pigmented ink. The heavier ink film will require the application of more spray powder to avoid setoff.
     
  5. alibryan

    alibryan Senior Member

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    May 2014
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    Location:
    Pacific NW

    Hi Daniel,

    Since you haven't mentioned any set-off issues I'm guessing the only problem you're having right now is with the rough feel of the sheet after printing. Without having to change anything that you're currently doing; the easiest and best solution to your problem is to run your sheets back through the press with the impression of one of your units turned on.

    After you've finished putting the last pass on your job, do a dry run as if you were printing again but this time with no water or ink (and no powder of course), using only the impression. This will collapse (or smash) the powder capsules on the sheet and make your sheet smooth again.

    I realize it's an added pass through the press and that it will take additional time, but the good news is that you can run the job as fast as you like - and it works.
     

  6. mantman

    mantman Member

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    Location:
    Greece
    There is a new batch of coating powder that is water soluble, meaning that you can print one pass normally and second pass with water on plate to take away a large portion of powder from sheet, also there is the option of drying additives
     
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