curling problem when running AQ

Discussion in 'Komori Printing Presses' started by glenn lamarche, Jun 20, 2011.

  1. glenn lamarche

    glenn lamarche Member

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    I have a problem with curl We run 60# stock most of the time curling when we apply coating does not seem to matter what speed or temp of the dryer or Ir setting I am going to try some low curl coating witch I did not seem to need before ? any one have any suggestions? I am running a komori LS29 six colour five years old I have been running this machine since it was new HELP !!
     
  2. RichardK

    RichardK Senior Member

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    Sounds like your viscosity is too high - have you tried reducing it? And what about your decurler, is it on? Is it clean? Is it sucking or blowing (don't laugh I had the same issue on our L626, seems like someone had left it in blow mode!)
     
  3. glenn lamarche

    glenn lamarche Member

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    decurler is not on the curl is up not down , and the viscosity is at the min 12 seconds on a number three zhon cup . the supplier sugested 14 to19 so we are below that ( what about the dryer )
     
  4. RichardK

    RichardK Senior Member

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    Decurlers don't just act in one direction. Regardless of curl up or down they still flatten out the sheet. Are you running the coating off the backedge of the sheet or does it stop short?
     
  5. glenn lamarche

    glenn lamarche Member

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    No the coating stops short of the back of the sheet do you suggest using the decurler ? We are running a C1S 60# sheet is it possible that it is the paper .We do not have curling on any other sheet .
     
  6. RichardK

    RichardK Senior Member

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    It'll probably be a long grain ... we get good results with short grain ie very little curl. And, yes, I'd use the decurler but take care to adjust suction so you don't get curl in the other direction.
     
  7. rolandman

    rolandman Senior Member

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    C1s has always been a fuker for curlin whenever ive run it, not sure if other have similar experience..
     
  8. turbotom1052

    turbotom1052 Senior Member

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    are you coating with a roller coater or anilox coater? if its a roller coater then i would experimenting with the amount of coating your laying down. Be sure coating is as thin as you can make it without slinging and try experimenting with your drying system. Measure how thin the coating is with a zahn cup and record readings so you can get repeatable results I prefer to run with very little IR and dry the sheet mostly with hot air. By turning down the heat you just might be able to help the curl as the sheet wont "tighten up" as much as the hot air hits it.
     
  9. Lignum

    Lignum Member

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    We stopped using aqueous coating on 60#, and now use toyo varnish, no curl anymore, dries extremely fast. We don't rack any job either, we treat it like it coating.
     
  10. Kaoticor

    Kaoticor Senior Member

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    One simple thing you can try is to double check your unit waters. I have seen some operators use the same ink/water balance with coated papers that they have used for a previous run of uncoated. If you are running a coated stock with a coating pass, you might be able to run with less water than with uncoated stock depending on your fountain solution. The little bit you can lower your balance can help out sometimes with the curl.
     
  11. Higgins428

    Higgins428 New Member

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    It looks like you've solved your issues on 60lb with the varnish but a couple things as a coating supplier that I've seen help. Depending on whether you have an annilox system or roller system, run your viscocity lower to reduce coating weight on either, but more importantly run a high solids coating to help avoid curl. Coating Weight is only adjustable with viscosity on your annilox system, but the roller coaters we've changed through pressure settings and roller durometer. Kaoticor makes a good point regarding water settings when running coating. Also run the coating as far to the edge of the sheet as possible to even the moisture on the paper fibers evenly. It tends to curl on the ends more without even distribution of moisture. Also load temps on first side pass are recommended to be around 95 degrees or a bit higher, but nothing over 85 degrees on second side pass. Air movement over the sheet will help a ton more than any IR heat with the coating. If you would like a troubleshooting guide feel free to shoot me an email and I can send one over to you. Hope this may help on other stocks if you are getting sheet curl.
     

  12. nightshifted

    nightshifted New Member

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    My quick guess would be too much IR and HAK. I, like Turbotom, prefered almost no heat at all when using a tower coater, which I am guessing you are using. Not thinning your AQ correctly will also bite you on the older tower systems. If you are thinning with straight h2o only, that will inhibit your coating drying. You may already know this but operators will do themselves such a service by just simply following manufacturers suggestions. Every coating maker I have dealt with says 75%/25% ratio of water to alcohol mixture for thinning AQ and try to stay around 17-20 seconds using #3 zahn. If you are constantly just adding a cup of water only, not only do you get the 12 second visc, but also a deep drying-inhibited coating. Slow curing will cause your corners to pull up and try to curl over itself, compounded dramatically as the wt of the stock diminishes. Add your HAK on high heat and acurling you go. 12 seconds using a #3 zahn, wow. With that viscosity, I am more surprised ink picking on coater blanket is not your #1 problem.
    I use 2 Harris/Bruno anilox coaters on my 840 perfector and we can get by using that low visc without picking off only because it is UV curing the ink before I hit the coater. But how you are doing it I cant imagine. Anyway, another suggestion is try a diff coating variety. Kelstar makes a w&t coating that is extremely user friendly, I believe it is 548. Get your coating rep in there pronto whether Kelstar or whomever you use. If he is worth a damn, he will be all over this. If not, other reps will for your business. That is what they are for. Use them. Anyway, hope this helps out some and it could always be worse. Someone out there is still no doubt using Kentyckyshine roller train coating through their last printing unit and trashing roller ends due to a helper that forgot to use the retarder he was told was extremely important to not forget. More so, especially since he replaced a fella who couldn't seem to remember the retarder either.
     
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