Color dropping out on Mimaki JV33-160

[KellyP12]

One of the yellows keeps dropping out randomly while printing. At first, I assumed it was caused by air in the lines somewhere. So I syringed it and it would work for a time and then drop out again. I then replaced both the yellow dampers. Problem still happened. I just tried swapping the yellow and cyan dampers. After an ink fill to flush the lines and a nozzle wash/cleaning, the issue stayed in the same location rather than following the damper. The yellow is now printing fine during the test draw and the cyan (now located in the yellow's location) has dropped out. So I now know (I think) that the problem is not anywhere before the damper; i.e. an air in the line issue). Can anyone help me figure out what my next move should be? Do you agree that it is a post-damper issue? What should my next steps be to troubleshoot / solve this?

 

[Solventinkjet]

The membrane that keeps the channels separate in the head may have been breached which would cause this issue. You could test this theory by flushing cleaning solution through the yellow channel with a syringe. If you push the solution through one channel and it comes out of 2 channels, the head is fried. If you push the solution through one channel and it comes out only 1 channel, something else is happening.

 

[KellyP12]

I don't think that could be the problem. If I'm understanding you correctly, this would be if the channels were mixing. The channels remain separate. Its just the one specific channel drops color, no matter what damper I have in that channel. Also, I'm not sure that it makes a difference, but I left out before that I'm using a bulk ink system with only 4 cartridges. This is split into the 8 channels after the cartridge.

 

[FLAGLOFT]

I have a mimaki ds-1800 that has had a similar problem. I turned out to be the pump on mine, or the cap could be clogged.

 

[Solventinkjet]

I don't think that could be the problem. If I'm understanding you correctly, this would be if the channels were mixing. The channels remain separate. Its just the one specific channel drops color, no matter what damper I have in that channel. Also, I'm not sure that it makes a difference, but I left out before that I'm using a bulk ink system with only 4 cartridges. This is split into the 8 channels after the cartridge.

Woops. I was thinking of a Mutoh color configuration not a Mimaki. You are correct. If the membrane was broken you would see cross contamination in the yellow.

It could still be damage inside the head causing the issue but I would start with a new cap top and check that the pump is working correctly. If the head is on the older side, 4 years +, it could be ink build up in the manifold causing the ink flow to be choked. Flushing sometimes fixes that issue and I have also fixed it by just replacing the manifold. This is only something you want to do as a last resort because it is not a standard procedure recommended by the manufacturer and it can cause more damage.