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Uneven Print length on JV33

Discussion in 'Mimaki' started by Rooster, Nov 8, 2009.

  1. Rooster

    Rooster Very Active Member

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    Feb 22, 2008
    Edmonton
    Here's the deal. Customer supplied artwork for a pop-up trade show display.

    Printing the graphics on Intellicoat's PosPro300 polycarb media and the print lengths are coming out different by at least 3/8ths of an inch between panels. Since the graphics contain both horizontal headers and footers that need to line up as well as text that runs across multiple panels this difference is unacceptable.

    I set the artwork up with an outline around the entire print area so that the media would always only move the amount necessary for the next print head pass. ie: There are no blank areas that would see the media advance to the next area that has something to print.

    The media has a matte finish coated print surface, but a glossy polycarbonate back to it. All panels were printed at the same time and used the take up reel. No adjustments were made to the media feed compensation other than the initial check prior to printing the first panel.

    Printing was done @ 720x1080 bi-directional 12 pass using wasatch rip.

    Has anybody had this issue before? Did you manage to solve it?
     
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  2. insignia

    insignia Very Active Member

    Did you try printing without the takeup reel to rule out tension from it causing it? And I know it sounds obvious but start with the basics, are you 100% sure each tile is the indentical size?

    I will say that PosPro 300 and 200 are very very finicky when it comes to media compensation on the JV33. On our JV3 we have no issues with it, just dial it in and go, but we've noticed that's not the case on the JV33 and throughout the length of a print we may need to make adjustments to the media comp a few times. The takeup reel makes this worse.
     
  3. Rooster

    Rooster Very Active Member

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    Feb 22, 2008
    Edmonton
    Yes, all the files were created from the same multi-layer photoshop document. Identical file resolutions, sizes, etc. The files all line up perfectly on-screen. I saw no indication of banding anywhere on the prints that would indicate slippage and as mentioned in the original post the media compensation was adjusted just prior to the start of printing, but not during. Both panels were printed as a single ripped file. I double checked the layout file and no scaling was inadvertently applied in the rip.

    The strange thing is of the two panels I've printed, the first panel which didn't use the take up reel until it had printed far enough to reach the take-up reel, is the longer of the two. I would have expected the exact opposite with the tension applied from the take-up system creating longer prints and not shorter.

    The 6 - 8 foot tall vinyl banners printed on smooth finish 13oz double sided show a maximum of 3/32" difference, but they were not all created from the same master file. Most are within 1/16th - 1/32nd of an inch of each other across 8 feet. This certainly hints that the PosPro media could be the culprit and are within a range that would workable on this project if I could get the same results from the PosPro.

    My service manual lists nothing in the way of print length or media feed calibration. Is there any way to calibrate this to make sure you're getting the right length prints? I know it was possible on my older epsons.
     
  4. Rooster

    Rooster Very Active Member

    1,209
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    Feb 22, 2008
    Edmonton
    Update, taking the take-up reel out of the equation brought everything within tolerances and all the panels now line up within 1/32nd of an inch to each other over the 8' height.

    I moved a work table over to front of the machine and had the prints roll out onto a bunch of old 3" tubes to further reduce friction and prevent the pieces from bunching up on the floor and gathering dirt. Think assembly line or shipping rollers to get an idea of the quick and dirty set-up I came up with using old media rolls.

    The poly media was definitely part of the problem. I think the smooth finish back prevents the friction feed rollers from gripping properly. I did another job that had 8 - 8' vinyl banners. Just for shits and giggles I did two without the takeup reel and then 6 with and they were all the same length.

    This worked much better than my local Mimaki tech's suggestion which was (of course) "buy a flatbed printer".
     
  5. insignia

    insignia Very Active Member

    Awesome, good to know. The takeup reel can cause that to happen, especially if you have the clutch tightened down too much so it's pulling too hard.
     
  6. Printhead

    Printhead Member

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    Dec 1, 2008
    I have this problem too on my JV5. I guess you found the source of your problem, but let me add, I've seen significant (.25" ~ .5") length difference when comparing tiles, and the reason was I let some of them too long in front of the heater. Since the clutch is pulling constantly it can stretch tiles. So, if you have an external heater you should be careful about heating all of the job equally.
     
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