JV5 cross contamination

[Robert72]

Dear Fellows,

I don't know if this is a known problem, but from time ago, I suffer ink cross contamination on the JV5 printheads. I start printing and the yellow begins printing black some nozzles till it's completely yellow after some passes.

This behaviour have ruined lots of prints, as even if I pause for cleaning, after that cleaning, the yellow starts again printing some black bands. This is not in every head, it's mainly on 3 and 4.

Can the dampers be guilty? May the damper valves don't close 100%? or is it due to cappings? All capping and pumps tubes are clean.

Thanks,
Robert.

 

[Vinylman]

Unless I am totaly mistaken the ink lines from the cartridges to the print heads are totally separate.
Therefore, any contamination is happening on the print side of the head. This can be caused be many things. Have the heat, humidity changed inside your print area recently? Controling static electricity is VERY IMPORTANT! It could be as simple {YA, RIGHT} as static build up on the bottom of the print head. It does NOT take much static to deflect the micro burst of ink from one or two jets to be attracted thus causing a contamination issue.

Something else to consider is the cleanliness of the print heads. Are they totally clean?
Are the "wiper{s}" new and perfect?
Is there ANY build up around the print head of old ink, or dust particles? Cleanliness is paramount to getting good results.

Maintenance is everything!

 

[SE SignSupply]

The problem you are describing happens occasionally on the Mutoh valuejet series (same printhead). We find that weather changes, or a low cartridge often are the root cause. Low pressure forms in the ink lines, or high pressure in the machine environment, backs up waste ink into the printhead.

Users that run their machines more frequently tend to avoid the problem.

 

[Jeff South Florida]

This is common with the new Mutoh and Mimaki 1 head and 1 cap system. The ink is wicking from one color to the other. Usually a lower volume cartridge gets contaminated. Check the bottom of the head is clean. Make sure there isn't a fiber on the nozzle part. Next would be the cap is hitting the bottom of the head. Check that the center of the cap is not swollen or contaminated.

 

[Rooster]

Reset your cap height. It's sucking ink up off the waste pads.

You just need to seal the head to the capping station's rubber lip, but not so far as to have the head contact the sponge(s).

 

[thewood]

Does the JV5 even have a sponge in the capping station?

 

[Robert72]

The thing tells Rooster can make sense because I've seen the cappings go really high when parking the printhead. They push too much against the printhead.
Regarding the pressures, the JV5 has valves on the cartridges to close the lines when not printing. Also, the dampers are different. They have anothe valve which open under the printhead demand, so the default state is closed to avoid ink spill because the cartridges ares higher than printhead adn the gravity would make the ink drain down. So I don't think the cross contamination can be due to different pressures at cartridges level.

Anyway, I'm trying to exchange the 32 dampers for new ones, but the price of the originals is way high to me, and the aftermarket I've tried don't seem to be very reliable.

Thanks to all. I'll keep informed.
Robert.

 

[SE SignSupply]

The thing tells Rooster can make sense because I've seen the cappings go really high when parking the printhead. They push too much against the printhead.
Regarding the pressures, the JV5 has valves on the cartridges to close the lines when not printing. Also, the dampers are different. They have anothe valve which open under the printhead demand, so the default state is closed to avoid ink spill because the cartridges ares higher than printhead adn the gravity would make the ink drain down. So I don't think the cross contamination can be due to different pressures at cartridges level.

Anyway, I'm trying to exchange the 32 dampers for new ones, but the price of the originals is way high to me, and the aftermarket I've tried don't seem to be very reliable.

Thanks to all. I'll keep informed.
Robert.

Interesting...learned something new today!