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HP L25500 :: Print quality issues (spitting?)

Discussion in 'Hewlett Packard' started by GP, Jul 17, 2013.

  1. GP

    GP Very Active Member

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    Every so often, when printing adhesive vinyl (in this case 9751RA) - we get these low quality print results, almost as if the heads are spitting.

    As you may see from the pictures, we were running some color tests. The green, which happens to be on the outside edge of the material roll has the spitting issue. The pink, which is just inside the that snipe, has a consistent ink pattern/resolution. I am not positive that this edge is the issue (contamination). In the past, it can be randomly throughout a large print.

    Any ideas what causes this? Heat/humidity?

    It is currently 75 degrees in the print room with a 53% humidity.

    Thanks for your time.
     

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  2. P Wagner

    P Wagner Very Active Member

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    This appears to be ink coalescence that is occurring. It is more difficult to control the media temperature on the edges of the printer platens than toward the center, due to air flow and other considerations. When the edges of the print media are cooler in the print zone than the center, ink can coalesce (this is where larger drops can form by merging smaller drops together). The question then becomes, what to do about it? 1) Attempt to raise the heater setting in the Drying Zone - but this heater maxes out at 131 f. 2) Print at a higher pass count - this puts less ink down per pass and gives the heater more time to dry the ink, but it slows down throughput. 3) On the L26500, use the Inter-Pass Delay value introduced in the latest printer firmware. I don't believe that HP has put this function into the L25500 firmware yet. (Ink Menu > Image Quality Maint > Inter-Pass Delay). 4) Build your media profiles to use less ink, or minimize the use of large dots. 5) Print toward the center of the media whenever possible.
     
  3. dypinc

    dypinc Very Active Member

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    Is that on Avery material. I have seen coating problems that look very much like that. You could do more passes, unidirectional, or redo your CM for lower ink levels.
     
  4. GP

    GP Very Active Member

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    Thanks to you both.

    I was printing 9751RA on a slightly modified 9551 profile (which quite frankly, always had the same results).

    In those attachments, we printed 10 pass. Boosting to 12 pass seemed to do the trick, even on the edges.

    But I will try to experiment with ink usage to nail a 8-10 pass. I really need to find some time to optimize our profiles. All of them are a little off in one way or another - but on top of being too busy - I find profile management intimidating.
     
  5. The Sign Factory

    The Sign Factory New Member

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    Solve it?

    I have been dealing with this for months now. I was wondering if you found an answer that worked for you? We and HP and a few others keep trying but no real answers. Thanks! DeAnn
     
  6. GP

    GP Very Active Member

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    Yes - I just increased the number of passes. Since then, I haven't had a problem. Nor have I had the time to properly profile the material at 10 pass, unfortunately.
     
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