C452 Light patch on halftone prints

[habik]

Hi There

Have MF451 (Bizhub C452) that has patching running on the bottom of the page. It happens on all colors.Turned paper 180 degree patching still happening on the bottom so it isn't the paper. 450k on Transfer belt but no visible patchy marks or any marks in fact what so ever. My eyes are sharp but don't see any obvious movement of transfer belt during the door open. Stabilization runs fine. Cleaned HV contacts on ITB + TR + inside machine( not on the back where HV board sits though). Cleaned IDC's front and rear- Re-run Stabilisation background reset and |Gradation. reboot - Trouble Reset - Checked again ITB for any broken/ cracked primary roller brackets. Nothing obvious. So I concluded either HV board or Transfer Belt or Transfer roller. Going to change ITB, just wondered if anyone had this so I don't run 3 times to a client.

Many Thanks see attached pdf.MF451 HALFTONE 1PC BK.pdf

[Max]

Re: C452 Light patch on halftone prints

measure the distance between the patches and take it from there. Is it the same on all colours or just K? I would say your K dev unit had it as the solids are very uneven. If i had to guess I would go for the image belt or fuser belt if the patches are not too far apart.

[habik]

Re: C452 Light patch on halftone prints

All colours same place same spot sloght variation in size




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[Dougtech]

Re: C452 Light patch on halftone prints

I see the sample has mixed colors - what do the individual CMYK test prints look like?

[habik]

Re: C452 Light patch on halftone prints





Back on site. Changed ITB and TR

problem persists


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[habik]

C452 Light patch on halftone prints

Replaced paper different brand. Problem remaining. Doesn't do it at all on A4. Tried running single color A4 cyan, magenta, yellow all good.

So it is definitely A3 issue as it happens on 2nd half.

Machine just passed 1 million. Data from Listoutput:

Transfer Roller 431k - Changed
Transfer Belt 48306 - Changed
CMY IU's - 1380M (43k) Changed recently
Drum K - 1521M (50k) Changed recently

Taking new dev and fuser as that is the last bit before I take machine apart.
Dev K - 700k -
Fuser 281k

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[EarthKmTech]

Re: C452 Light patch on halftone prints

fusing loop actuator clean and unbroken ?

tried increasing printer reg loop from tray 1/2 ?

Enormous groove worn into grey guide bellow IDC sensor housing altering paper path length ?

[habik]

Re: C452 Light patch on halftone prints

Thanks EarthKmTech. I will check that groove next time! And will keep your tips in mind.

It turned out to be fuser. I'll post pics later.

Funny bit is that when I run paper 3 times as blank copy and tried halftone the issue wasn't showing. Meaning paper got harder grains shorter so not much movement and that lead to the fuser but I never had one to go at 280k. They last 2x as much.


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[Max]

Re: C452 Light patch on halftone prints

measure the distance between the patches and take it from there. Is it the same on all colours or just K? I would say your K dev unit had it as the solids are very uneven. If i had to guess I would go for the image belt or fuser belt if the patches are not too far apart.

I new it :-)

[habik]

Re: C452 Light patch on halftone prints

I new it :-)

Well

My experience is that patches travel. Like drum length fuser belt length dev lenght ITB or TR length. So when you print 20 A3 in a run you'd see the patch moving. Since it looked like stain mark I thought it is paper.. Changed paper and stain was different in size and shape but still in the same spot.


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[hotfuser]

Re: C452 Light patch on halftone prints

Well

My experience is that patches travel. Like drum length fuser belt length dev lenght ITB or TR length. So when you print 20 A3 in a run you'd see the patch moving. Since it looked like stain mark I thought it is paper.. Changed paper and stain was different in size and shape but still in the same spot.


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Was the fuser unit rippled on the LFR (bubbling/coating coming off) this is quite common on high milage units.

[habik]

C452 Light patch on halftone prints

Was the fuser unit rippled on the LFR (bubbling/coating coming off) this is quite common on high milage units.

Yes. Not a heavy wear. The fuser done 281k only.

Whats the cause? Age!?


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[hotfuser]

Re: C452 Light patch on halftone prints

Yes. Not a heavy wear. The fuser done 281k only.

Whats the cause? Age!?


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yes mate it is just age

[habik]

Re: C452 Light patch on halftone prints

Getting old I am,
cheers everyone have a nice weekend!



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[EarthKmTech]

Re: C452 Light patch on halftone prints

This engine destroys fusers when used exclusively on A3, they will start to crumble the pink sponge under the sleeve at around 40-50k and by 100k the entire sleeve shreds. Absolutely nothing can be done about it either, had multiple brand new machines out of the box doing it at one customer till we gave them something with a real fusing unit - not this instant on induction rubbish.

The more A3 a customer prints the more likely the fuser is to fail before end of life.