Toning problems on Mithsu D3000 6-color

Discussion in 'Mitsubishi Printing Presses' started by Miniwheat, Oct 3, 2013.

  1. Miniwheat

    Miniwheat Member

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    I've started having toning problems in all 4 colors. Magenta is the worst, but cyan and yellow are problems as well. I recently took 8 working days off to deal with a death in the family, and since returning the toning has shown up. I've checked form roller stripes, changed fountain solution (currently around 2000 conductivity), and now I'm at a bit of a loss as to what else I can do. Any help would be appreciated. Room temperature is usually around 75-78 degrees, humidity between 40 and 50%.
     
  2. turbotom1052

    turbotom1052 Senior Member

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    couple
    of things to check....
    1) temp. of fountain solution in the water pan as well as in the tank. I like to see it @ around 60 to 62 farenheit but we keep our shop at closer to 70 degrees so in your case id say you want to see around 69 to 70 fahrenheit in the water pan.
    2) temp. of roller chillers if so equipped. This i run @ around 68 fahrenheit, but again we keep our shop much cooler than yours and 68 may not work for you. You may want to try 72 degrees as a starting point.
    3) 2000 seems pretty high to me as a starting point for conductivity unless your water is measuring 1000 plus coming out of the tap. We run RO water so we mix our solution to start at 1000. The rule of thumb is to mix it to about 800 over your tap waters starting conductivity. You may want to monitor your tap water over time to be sure that you have some consistency you can count on, and if you see alot of variation think about doing something to condition your incoming water. Again we us reverse osmosis water so our dosatron always hits 970 to 1000 when starting out with a fresh batch. We do not have auto dump so i like to drain and replace if conductivity exceeds 1600.
    4) try and determine if this toning issue began with a new batch of plates as ive seen bad plates be the cause of this sorta problem.
    3) a good calcium rinse of the rollers wouldnt be a bad idea.
    Good luck tracking down your problem and keep us all posted.
     
  3. juanjo

    juanjo Member

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    Hello my name is Juanjo, good for three years working as an instructor for mitsubishi distributor in Spain and I have 15 years as a graphic machinery technician Kba, Ryobi and Presstek.
    The problem that could also be due to the rocking motion of the form rollers if your machine has them.
    Another cause could also be due to the roller bridge linking the inking system and dampening system, when the roll does not turn smoothly because the system that leads inside is defective can take that problem too.
    I hope it helps.
    Greetings.
     
  4. Miniwheat

    Miniwheat Member

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    So at last here's an update to my toning woes. I'll begin by addressing turbotom's points. My fountain solution temp. is around 62 Fahrenheit and my roller chillers run around 59 Fahrenheit. There's been no changes with those, so I don't think they're the problem. Next, we did dump the fountain solution and remix to a conductivity of about 1500. We also use RO water so there is no variation when we dump and make new. I gave it a good calcium wash (no effect) and if it was bad plates we've run through them long ago.
    Investigation of the metering rollers revealed that every one of them is low (shrunk) on the ends, so adjusting them to not wash out on the ends produces such tightness through the middle that I must run them in the 60+% range to print. I replaced the magenta metering roller with the one new one that we had and it now runs in the mid 30% range. Problem (mostly) solved.
    Next I restriped every roller in every unit. That made a HUGE difference.
    Lastly, I've discovered that by moving the dead point forward or backward I can make what little toning I still experience go away...usually.
     

  5. turbotom1052

    turbotom1052 Senior Member

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    when you adjust your metering rollers to correct the shrunken ends are you making a skew adjustment or a parallel adjustment? Ive found that when the ends shrink you need to adjust the skew to bring the rollers closer to parallel. Changing the dead point although effective is just putting a bandaid on a gunshot wound. On a final note id like to say that after many years of running many different manufacturers presses I've found the the mitsubishi diamond presses to be the very worst for holding roller settings. This is the reason for checking and adjusting on at the least a monthly basis.
     
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