Why do these nozzles come and go?!?!

[x2chris7x]

So we've been having this problem for a while now... When running a nozzle check all nozzles are good, except 1 bank of black. Most times more than half of those nozzles are missing, but it never stays consistent... On Monday I ran a nozzle check before printing and all nozzles, even the bank of black that is normally missing, were there... Nozzle check was perfect!

I ran a few prints then another nozzle check, this time I was missing about a quarter of the nozzles on that one bank of black. I ran a few more prints and now i'm missing more than half... The prints are also noticeably lighter when the nozzles start to go out...

Anyone know what the problem could be? This is extremely frustrating!!

 

[rjssigns]

IIRC somebody posted in regards to black having issues. Something to do with the carbon black content of the ink causing nozzle drop-outs. Seemed to be a difference between OEM and 3rd party ink.

First thing I'd look at is how many "shots" on the head. If the count is low then I'd make sure cables are seated, captops are good and sealing etc... Check the easy stuff first.

 

[RG]

Make sure that ink is flowing freely through the cap top and pump tubes. Use a swab to moisten the rubber on the cap top. Make sure that nothing is stuck onto the printhead. Look for any air bubbles in the problem ink line. If the MS is in good shape, and if the drop-out is in the same bank every time, I would replace the damper and o-ring for that bank. I had a similar problem a couple of years ago. The Mutoh tech guy couldn't get all jets firing, so he replaced the printhead. Thank goodness for that warranty.

 

[x2chris7x]

We actually had the head replaced about 2 yrs ago... along with dampers... and Capping station. The nozzles are definitely not clogged b/c, like I said, on Monday I ran a nozzle check that was perfect... but the more we print, the worse it gets...

I was leaning toward dampers... but Im not sure.

I had read a post a few months ago that said that the lines on the capping station may be clogged and preventing the pump from being able to pull the ink through the head during cleaning... They said this could cause the problem we're seeing b/c the black ink is more dense than other colors... We disassembled the capping station and cleaned out all the lines, but that didnt not help.

 

[MuhammadOsta]

i had the same problem with black (on Mimaki), sometimes even soft cleaning will open all the black nozzles.. do a test print all fine, leave it for a couple of minutes and will start to miss a lot of them. print some files and miss some again.. i checked the black ink valves, tubes, dampers.. all seem fine. so what was the problem? it turns out that mimaki ****ed up with the ink patch! all the black ink from the same patch i purchased caused the same problem. changed the ink, do some fill-up and cleaning, never had the problem again. i couldn't believe it, so i re installed a new one from the same patch i had the problem from.. the same thing again! i ended up trying another three bags (each 2Liter, very expensive) and all got the same problem. by the way, the ink was "deep black" which is very different chemical than "black", i used to install expired "black" ink with no problem what so ever.. where "deep black" with more than 4 month left to expire did this problem.

 

[WalkerP]

Change your damper on that channel and see if that fixes it. Sounds like the culprit to me.

 

[Solventinkjet]

Inconsistent nozzle firing is almost always an ink flow or maintenance issue. I would replace the dampers, cap top, and wiper if they haven't been changed in a year or more and check the pump for clogs. Clean the bottom of the head where the cap top meets the surface to get rid of any ink build up that may be breaking the seal between the head and cap top. If the machine is in the older side, I would replace the cap slider as well as the pegs that it slides on erode and cause the cap top to not seal properly.

If all the maintenance parts are working properly and clean, and there is no air in the ink lines etc. the head should fire properly. If not, you could have a broken membrane inside the head which means it is unrecoverable. This happens on older heads, heads using full solvent inks are more separable, heads that have been flushed too hard, and sometimes just bad luck.

 

[cmwpmm]

Sounds like air in the lines to me. Usually when I get air, my test prints start out looking great and after some solid printing lots of random nozzles begin to drop out. I'd check there first.