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  1. #1
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    Question C75 White lines in gray

    Hello,
    I can't get rid of these 3 white lines, they are only visible on gray (100% black is ok), the CMY output is fine
    I've changed the developer assembly, the black drum, the fuser, but it doesn't affect the result. They always appear at the end of the paper (SRA3+, 320 460 mm, 12.6" x 18.1")

    If I use a shorter SRA3 paper, the last line is cropped down, but the first 2 lines are still visible.

    Any idea what causing this?

    (I know there are several other issues visible, but currently this is the most obnoxious)

    sra3plus.jpg

  2. #2
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    Re: C75 White lines in gray

    Process direction?
    Lead edge?

  3. #3
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    Re: C75 White lines in gray

    Quote Originally Posted by xcopytech View Post
    Process direction?
    Lead edge?
    The left side of the picture is the lead edge. The lines are formed on the trailing edge

  4. #4
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    Re: C75 White lines in gray

    Do you have this problem at 80gsm paper?

  5. #5
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    Re: C75 White lines in gray

    Quote Originally Posted by xcopytech View Post
    Do you have this problem at 80gsm paper?
    I only have this size in 250gsm and 300gsm, and they look similar.
    I've tried an A4 80gsm and a 300gsm, and it seems like the heavy stock have sharper lines (maybe just because its darker?)

    Left 80gsm, right 300gsm. both printed with A4 SEF (the 3 lines are not visible here, they only appear above A3 size)

    Fiery_Grayscale_002.pdf

  6. #6
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    C75 White lines in gray

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    Re: C75 White lines in gray

    Quote Originally Posted by Neocortex View Post
    I only have this size in 250gsm and 300gsm, and they look similar.
    I've tried an A4 80gsm and a 300gsm, and it seems like the heavy stock have sharper lines (maybe just because its darker?)

    Left 80gsm, right 300gsm. both printed with A4 SEF (the 3 lines are not visible here, they only appear above A3 size)

    Fiery_Grayscale_002.pdf
    are you declaring the proper WEIGHT on copier and file to print?

    the fact it prints good on lighter gram paper indicates TO ME that the weight isn't set right for the fuser temp/speed

    kinda hard to tell from your profile:

    are you a tech?

    what machine have you been formally trained on?

  7. #7
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    Re: C75 White lines in gray

    It's look like impulse banding.
    It should be visible also on other colors.
    Cyan defect should be first at app 20mm from lead edge.
    Print cyan, magenta 40% halftone on 300gsm paper and check for defect

  8. #8
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    Re: C75 White lines in gray

    Quote Originally Posted by xcopytech View Post
    It's look like impulse banding.
    It should be visible also on other colors.
    Cyan defect should be first at app 20mm from lead edge.
    Print cyan, magenta 40% halftone on 300gsm paper and check for defect
    Lead edge is on the right side
    magenta_40.pdf
    cyan_40.pdf

    Yes, there is a slight banding exactly 20mm from the lead edge. Thank you! Should I clean the ROS windows? Or run the SIQA Auto Density Uniformity tool?

  9. #9
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    Re: C75 White lines in gray

    The uniformity tool didn't fix it

    uniformity.jpg

  10. #10
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    C75 White lines in gray


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    Re: C75 White lines in gray

    Impulse banding is more of a "physical" defect, in that the paper (or a component) isn't moving quite as smoothly as would be ideal for best print quality. It can be quite problematic to fix for the end user. And in my experience, it can be worse for heavier papers because they are so much stiffer they tend to "jerk" around more as they travel through the machine. PARTICULARLY at the trailing edge of heavy papers, because as it travels through the paper path, which is pretty flat but not completely flat, as the trailing edge clears one set of feed rollers, or the transfer roller or whatever, it can "flip" up ever so slightly causing a physical motion that can impact the toner before it is fused. And also, since you are on nearly the largest paper, it is in contact with a LOT of various roller points at one time, compared to long-edge-feed 8.5 x 11, for example. Lighter papers are so pliant, they aren't going to cause the seismic vibration heavier paper would.

    So, I think it is probably (unfortunately) fairly unavoidable due to it being physical "rattling" of the paper inside the machine. I came to that guesstimate based on the following:

    * Heavy wright paper
    * Large paper size
    * On the trailing edge
    * Only in lighter shades
    * What the marks in your image look like to me

    I would recommend running the paper slower, but at 250/300gsm, I suspect you are already running as slow as the machine goes.

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