Set-off on LS440

Discussion in 'Komori Printing Presses' started by Richie, Aug 8, 2012.

  1. Richie

    Richie Member

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    Hie guys we running a komori LS440 & we having problems with set off on the tail edge, in the corners of the paper. Have checked the nozzles & they blowing ok. Have also inrceased the quantity of our spray powder but the problem still there. The feed pipes are clean, we are running on IR and we using medium coated powder from Varn. The ink we using is Hostmann Steinberg Maxxima, running alcohol free on Varn Premier Fount GP. On paper we using Hi Q Titan. Anyone had a problem like this before or with idea on how to solve it will be greatly appreciated. Our paper joggers are knocking just enough to give us a good stack.
     
  2. NotAGooner

    NotAGooner Senior Member

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    Wedges in the corners might help but put them at the beginning and don't move them.
     
  3. Komory

    Komory Member

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    No alcohol is not very good.
    The main thing-is quicly drying inks,fine powder and rear(last but one) fans speed set to minimum .
    We used Flint 990 protect.(ls440
    machine without the long dryer and IR)-at any speed on any paper -never set off..
     
    Last edited: Aug 13, 2012
  4. turbotom1052

    turbotom1052 Senior Member

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    have you checked to be sure your powder unit is powdering the sheet all the way back to the tail? Some powder units are adjustable for sheet length via the powder unit itself. Other units interface with the press size presets and automatically adjust powdering length. Still others must be adjusted by a cam in the delivery to powder the full length of the sheet. If everything checks out with powder unit id be looking at how the sheet is delivering. As Komory mentioned you want minimum fan speed so as not to blow down the sheets too hard onto the pile. I also prefer to keep my pile height high so that the sheet doesnt have a really big drop to the top of the pile. Last but not least are you running reasonable ink densities with no more than 290% total ink build on your rich blacks? Keep in mind that if your inline varnishing you must add 100% to your total ink builds!!!
     
  5. Kaoticor

    Kaoticor Senior Member

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    Just as a side question, are you using coating? I'm guessing not but if you are, look there.
     
  6. Richie

    Richie Member

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    Thanks guys for your response, we seem to have overcome the problem. We have been using wedges and since we stopped using them things have changed for the better though we yet to be ok 100%. My question to Komory is that will fine powder be ok for matt paper? We using coated medium powder and we are not coating. As for our ink densities they are ok K= 1,10 C=0,85 M=0,90 Y=0,85. I appreciate guys.
     
  7. Komory

    Komory Member

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    I don't remember powder brand. some fine-grained from UK. suitable for matt paper. tried to use medium-grained,
    but it may lead to set off,especially starch-based powder.
     
  8. presselectronics

    presselectronics Senior Member

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    "we having problems with set off on the tail edge" this is a classic problem on Weko sprayers that were not timed properly. Also I would recommened to turn down any exhaust fan and use the smaller sealed powder bags in the 25 micron range.

    BTW, if it's a Weko, remember to clean out the powder bowl regularly and blow out the powder delivery lines to the spray bar a few times a year. Also make sure you clean BOTH filters on the Weko pump - people quite often miss the small carbon filter inside the pump.
     
  9. proslack

    proslack Member

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    If using a weko 1st. absolutely check that the spray bar has been timed correctly for its mounted position, at the vari-cam. the unit should come on and turn off at a precise location of the chain delivery gripper bar to the spray head. You can check if the unit is shutting off too early by manually increasing the duration length at your control panel. if that helps you might re-time the sprayer duration based on the varicam. 2nd. absolutely make sure your filters are clean, then at the weko unit manually check on your "P" functions that the air pressure expected is the air pressure that the unit is getting from the pump. Not more. The unit will blow the powder too hard essentially blowing it off the sheet, creating excessive overspray, and no matter how much powder you throw at it you will get set off. 3rd. if timed correctly, clean filters, proper air pressure, passing a black sheet through the press, you can inspect the powder transmission on to the sheet with a yellow light with room lights out. If you are not actually getting a good spray, you can increase the percentage of the powder delivery from the weko console "P" functions changing the ratio to higher than the factory setting. You say "what good is this i can just turn it up on my press console and I still have set off"?, changing the internal ratio of the weko delivers a different amount of powder at each rotation of the cam below the cone. try it you may like it.
     
  10. Yorkshire Gripper

    Yorkshire Gripper Senior Member

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    I've seen this on a 40 before, it was caused by air turbulence making the corners of the sheet flap. I got rid of it by disconnecting the micro on the back of the swan neck (naughty) so I could open it and see the sheet whilst adjusting air controls, as is usually the case in printing, less is better. Also changed the customer to a fine coated powder, result - sprayer setting down to normal, better sheet control, no set off plus the minders didn't look like flour graders after a shift :)

    YG
     
  11. Richie

    Richie Member

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    We using a GRAFIX DIGITRONIC 2000 not a Weko. Since we stopped using wedges the problem seem to be gone, we just have a little sett off maybe one sheet after 1000 which a layman can hardly see. But all the same will go through the settings again just to make sure we on track. Thanks guys
     
  12. Kaoticor

    Kaoticor Senior Member

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    I'm sure you have already checked it, but remember pile temp! Very important for setoff control
     

  13. turbotom1052

    turbotom1052 Senior Member

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    when i ask about total ink densities i misspoke. what im really referring to is total ink percentages. That is to ask on areas of rich black image what is the total value of the combined screens. This number should not exceed 290% when printing on a gloss coated sheet. A matte or silk coated sheet should be a little less and certain smooth surfaced uncoated sheets even less yet.
     
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