Vein like Black Marks in neven vertical Pattern Running through Print - Help needed Please

[J4cko]

Hi Guys,
Hope you can help please.

We run the same media on all of our HP Latex printers ( canvas media )

On one of our machines, we have had black vein like marks traversing vertically through the prints, in an uneven fashion. Like a squggly vertical vein.
I have attached a couple of pictures, not sure how clear it is to see.
But it is black vein like pattern which is ruing the prints.
We have swapped rolls, and it is not the roll.

It looks almost like the media is puckering as it comes through the rollers.
https://www.dropbox.com/scl/fi/nk41...ey=tz4zyehhcyapvrkycaez2kh2o&st=zhxs4lwa&dl=0

Nothing has changed, no settings, no new parts, same media

It almost looks like the print head is catching on the print, and the print is cockling
No heat settings changed

Puzzled to what it may be ?

Any words of wisdom massively appreciated

thanks in advance
kind regards
Jack

 

[MNT_Printhead]

That pattern kind of looks like what happens when ink gets on one of the pinch rollers.

 

[balstestrat]

I would say clean the bottom of your carriage. Maybe you have a piece of vinyl stuck there or something.

 

[J4cko]

It looks too distributed for that to be the case ? and it looks clean as it comes through the rollers, and if we feed media through, there is no marks

 

[J4cko]

sorry, that last reply was @ MNT ....thanks balstestrat , ...how exactly would we clean the bottom of the carriage ?

 

[J4cko]

i have just been informed that on the pinch rollers ( the one on the right hand edge, by where the carriage returns to ) , as been replaced yesterday. Nobody knows where the old / missing pink roller from the far right hand side is ? Could it be that the new pinch roller is causing this puckering of the media ? and/or that the old pinch roller is stuck somewhere inside ?

 

[balstestrat]

Turn it off. Pull out the maintenance cartridge. Inspect and clean the bottom.

Now important. Move the carriage leftwards to the middle. Push the cartridge back in and start the printer.

 

[J4cko]

Thanks Balstestrat, much appreciated. What would you suggest using to clean the underneath of the carriage ? ( apologies for any naivety )

 

[balstestrat]

Just take a look first if you see anything that shouldn't be there.

 

[J4cko]

Hi guys, the issue has manifested again. We have checked under the carriage, cleaned the edge guards.
Im sure my engineer also cleaned some sensor, and the wipe blade
This appears to be intermittent. But seems to occur when we do long print runs, and not on isolated or short runs

Our media has been the same for years
Our settings on the machines havent changed
We are just concerned what would cause this issue all of a sudden, and more often, mid roll, when printing long runs

Any advice, massively appreciated

We are trying to print without the edge holders now, but have used these for years without issue

kind regards
Jack

Please see the attached photos
Anything else we can check ?
thanks guys