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  1. #1
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    C6500 Exit Section Causing Smudging?


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    C6500 Exit Section Causing Smudging?

    Hi all,

    Trying to solve another issue on the C6500 and wonder if I'm on the right track. The image is a 18x12 sheet of 280gsm (sold as 14pt) C2S board (grain short), with the leading edge on the left.

    Observations:
    1) About 14 inches along the feed length, there's a pattern of repeated smudges in all colors (sorry only M+Y in this photo), and then it stops.
    2) It happens at the same spot on every sheet.
    3) It's hard to see in this photo, but the entire image is shortened by about 1/8 inch compared to the "correct" print above.
    4) It only happens on this specific thickness of paper. I've tried 14pt C2S of a different brand and same problem.
    250gsm of the same brand (sold as 12pt), or anything lighter doesn't create the issue at all.
    300gsm boards which are much denser, so thinner, don't cause a problem either.
    5) It can happen on 12 x 12" sheets of this same material if I test with that. It happens at about 9.5 inches in that case.
    6) If I try 12 x 9" sheets (short edge feed, grain short) of the same material, it doesn't happen.
    7) I can usually get 1 or 2 sheets to print before it becomes an issue (like the top "correct" one in this photo).

    What I tried:
    1) Removing the finisher and relay unit. No change.
    2) Replacing the soft exit roller/B (A03U892600) with one from another machine (slightly used, but in much better condition). This improved it somewhat. The image isn't shrunk, and the smudging looks different, but still starts at the same locations on both sheet sizes.

    I already had a brand new exit roller/B on the way, and I just ordered the 2 one-way gears for the exit section (A03U909701, A03U909502), so going to swap all that out and try again.

    Has anyone seen this problem before? Am I right thinking it's the exit section? I suspect that mostly because of the image shrinkage, and the fact that it's the same location every sheet.

    If it is the exit section, are there any other parts in there I should be looking at? Maybe the other exit roller with the white coating?

    Thanks in advance!


    Last edited by vickash; 06-15-2021 at 04:07 AM. Reason: Extra info

  2. #2
    Service Manager 10,000+ Posts
    C6500 Exit Section Causing Smudging?

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    Re: C6500 Exit Section Causing Smudging?

    Quote Originally Posted by vickash View Post
    Hi all,

    Trying to solve another issue on the C6500 and wonder if I'm on the right track. The image is a 18x12 sheet of 280gsm (sold as 14pt) C2S board (grain short), with the leading edge on the left.

    Observations:
    1) About 14 inches along the feed length, there's a pattern of repeated smudges in all colors (sorry only M+Y in this photo), and then it stops.
    2) It happens at the same spot on every sheet.
    3) It's hard to see in this photo, but the entire image is shortened by about 1/8 inch compared to the "correct" print above.
    4) It only happens on this specific thickness of paper. I've tried 14pt C2S of a different brand and same problem.
    250gsm of the same brand (sold as 12pt), or anything lighter doesn't create the issue at all.
    300gsm boards which are much denser, so thinner, don't cause a problem either.
    5) It can happen on 12 x 12" sheets of this same material if I test with that. It happens at about 9.5 inches in that case.
    6) If I try 12 x 9" sheets (short edge feed, grain short) of the same material, it doesn't happen.
    7) I can usually get 1 or 2 sheets to print before it becomes an issue (like the top "correct" one in this photo).

    What I tried:
    1) Removing the finisher and relay unit. No change.
    2) Replacing the soft exit roller/B (A03U892600) with one from another machine (slightly used, but in much better condition). This improved it somewhat. The image isn't shrunk, and the smudging looks different, but still starts at the same locations on both sheet sizes.

    I already had a brand new exit roller/B on the way, and I just ordered the 2 one-way gears for the exit section (A03U909701, A03U909502), so going to swap all that out and try again.

    Has anyone seen this problem before? Am I right thinking it's the exit section? I suspect that mostly because of the image shrinkage, and the fact that it's the same location every sheet.

    If it is the exit section, are there any other parts in there I should be looking at? Maybe the other exit roller with the white coating?

    Thanks in advance!



    what thickness are you setting it for.

    lighter weight doesn't smudge but thicker does..clasicc sign there isn't enough heat to bond toner to media

    more than likely exit assmm is not to blame

    also look at dev units looks more like backgrounding

  3. #3
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    Re: C6500 Exit Section Causing Smudging?

    Had similar problem few times.
    It mostly occur when thick paper is too stiff.
    Try this settings

    stiff paper.jpg

  4. #4
    Senior Tech 250+ Posts
    C6500 Exit Section Causing Smudging?

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    Re: C6500 Exit Section Causing Smudging?

    Toxic is right. This issue occurs with heavy media. Marking happens on the second transfer as the end of the paper comes off the registration roller. This causes media vibration and interferes with transfer.




    There is also under Process Adjustment for each tray, on the last page of the adjustment, the 2nd transfer and print speed settings. I've already gotten good results choosing:


    (Speed up)
    (2nd transfer pressure - low)
    (low CPM - low)




    The mentioned settings are the alternatives for your problem. If not, change the media.
    Nothing like day after day

  5. #5
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    C6500 Exit Section Causing Smudging?


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    Re: C6500 Exit Section Causing Smudging?

    Quote Originally Posted by tulintron View Post
    Toxic is right. This issue occurs with heavy media. Marking happens on the second transfer as the end of the paper comes off the registration roller. This causes media vibration and interferes with transfer.
    This is interesting, so maybe it's happening before the 2nd transfer, rather than after.

    I've tried CPM down and that didn't help. I already had the DC separation values at -30 from that guide. I'll try lowering the 2nd transfer pressure and see what that does.

    Thanks

  6. #6
    Certified Konica Expert 2,500+ Posts
    C6500 Exit Section Causing Smudging?

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    Re: C6500 Exit Section Causing Smudging?

    Are you asking about the light lines above the letter L in the pic?
    Swap black corona with yellow. Looks like a dirty Corona or grid that will show with extra voltage because it's set to thick.
    We know a thing or two because we've seen a thing or two.

  7. #7
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    C6500 Exit Section Causing Smudging?


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    Re: C6500 Exit Section Causing Smudging?

    Quote Originally Posted by Synthohol View Post
    Are you asking about the light lines above the letter L in the pic?
    Swap black corona with yellow. Looks like a dirty Corona or grid that will show with extra voltage because it's set to thick.
    Yes, those lines. I think I chose a bad example to explain the issue. It isn't the coronas. The entire image is 1/8" shorter on the sheet, as if the paper is being slowed down while the transfer roller still turns. It happens with all 4 colors.

    Quote Originally Posted by tulintron View Post
    Toxic is right. This issue occurs with heavy media. Marking happens on the second transfer as the end of the paper comes off the registration roller. This causes media vibration and interferes with transfer.
    Thanks for this clue. I noticed that on the 12.5 x 12.5 sheets, the defect was happening the same distance from the TRAILING edge as with the 12.5 x 19 sheets. I thought that was unusual, so I tried cutting slightly shorter 12.5 x 18.8" sheets instead. It ran 400 of those last week without a single problem. Still not sure exactly what's going on there, but at least I have a workaround.

  8. #8
    Senior Tech 250+ Posts
    C6500 Exit Section Causing Smudging?

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    Re: C6500 Exit Section Causing Smudging?

    Quote Originally Posted by vickash View Post
    Yes, those lines. I think I chose a bad example to explain the issue. It isn't the coronas. The entire image is 1/8" shorter on the sheet, as if the paper is being slowed down while the transfer roller still turns. It happens with all 4 colors.



    Thanks for this clue. I noticed that on the 12.5 x 12.5 sheets, the defect was happening the same distance from the TRAILING edge as with the 12.5 x 19 sheets. I thought that was unusual, so I tried cutting slightly shorter 12.5 x 18.8" sheets instead. It ran 400 of those last week without a single problem. Still not sure exactly what's going on there, but at least I have a workaround.
    Yes, you got a way to print without the marks. But this is characteristic of the printer when the paper is very stiff. If you test with another paper of the same size but lighter weight, the marks will not appear.

    I had a similar problem with a 250gm couche with inverted fiber. After cutting with the fiber in the correct position, the marks disappeared.
    Nothing like day after day

  9. #9
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    C6500 Exit Section Causing Smudging?


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    Re: C6500 Exit Section Causing Smudging?

    happens when you run stock too thick. maybe 256gsm but its too stiff. We found max weight on C6501 is 12PT. 14PT doesn't run. too heavy even if GSM is under 300gsm.

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