Mimaki JFX200 2513 Clear head keeps dropping nozzles

[CN Spots]

Has anyone had any issues with clear heads on their JFX losing nozzles? We have a Mimaki Tech (several, actually) who has been fighting this for over a year now. We are on our 4th! head and each one seems to only last a few days/week before a similar, but not exact, number of nozzles fail. They have tried everything they and I can think of to remedy this aside from a logic board replacement.

The last one was replaced Tuesday. Wednesday morning's nozzle test was perfect at 8AM. By 2PM the clear head was missing over 30 nozzles. It stops there. Never gets any worse or better. No amount of cleaning, flushing, purging or refilling does any good to bring them back.

The only noticeable change that they ever made to a failing head was increasing the voltage to the head. That brought a bunch back but not all of them. Mimaki HQ claims to have never encountered this issue before.
Any help would be appreciated! Thanks!

 

[Solventinkjet]

After the nozzles start to clog, do they come and go or is it the same clogged nozzles every time? If it's the former, I would suspect a pressure issue, sub tank issue, or other ink flow issues such as a clogged filter, bad valve, or air leak somewhere. If it's the latter, I would suspect a bad filter, contaminated ink, or possibly even the head is getting flashed with light somehow and clogging the nozzles. When was the last time you changes the primary filters?

 

[CN Spots]

Same ones go out and stay out but not the same ones for each new head. We DO print on foil from time to time but the original head lasted for years w/o issue. This last one saw no foil at all that day and showed the same symptoms in just 6 hours that the first head took years to develop. They know what we print on and how and said that nothing we were doing should be causing this.

Throughout this whole process they have replaced almost everything. Filters, back flow preventers, flushed out the entire clear ink system and added new ink, etc. The air purge valve on the front was suspect this time (small leak) and was replaced as well but did not help.

Another printer operator I work with thought maybe a wire had gotten crimped/damaged and that might be why the voltage increase helped somewhat?

 

[Solventinkjet]

Another printer operator I work with thought maybe a wire had gotten crimped/damaged and that might be why the voltage increase helped somewhat?

If that were the case I think you'd be blowing fuses left and right. Unfortunately it sounds like one of those tough ones. It doesn't seem to be a flow issue. And missing a few random nozzles would be very rare, if not impossible, to be electronic. That only leaves clogging in my opinion.

Do you know if they checked if the head carriage is level? Did they check the head height adjustment pin to make sure it's reading properly? If the head is too high, it can cause the lamps to cure the ink in the nozzle. If it's not level the same thing can happen. The fact that it's not happening in the other colors is interesting as well. Maybe the cap top and/or maintenance pump for that head is failing?

 

[CN Spots]

We had it leveled about a year ago. The white nozzles are fine and have never been an issue with any of the heads that were replaced. I should have mentioned this is a CMYK/ClearClearWW config.

During the last repair the tech did an ink wash with some higher strength cleaner and we noticed that there was some white ink flowing into the clear reservoir above the head (damper I think it called?). That prompted the back flow preventer replacement. We thought we had found the problem but that was not the case.

The fact that we get most of the nozzles back after increasing the voltage is the kicker. I'm looking at this like maybe it has a bad voltage regulator/gauge/senging unit.. whatever it uses. Could it be saying that its XX voltage when it really at X voltage and just needs more juice? And yes. I'm grasping at straws!

 

[Solventinkjet]

We had it leveled about a year ago. The white nozzles are fine and have never been an issue with any of the heads that were replaced. I should have mentioned this is a CMYK/ClearClearWW config.

During the last repair the tech did an ink wash with some higher strength cleaner and we noticed that there was some white ink flowing into the clear reservoir above the head (damper I think it called?). That prompted the back flow preventer replacement. We thought we had found the problem but that was not the case.

The fact that we get most of the nozzles back after increasing the voltage is the kicker. I'm looking at this like maybe it has a bad voltage regulator/gauge/senging unit.. whatever it uses. Could it be saying that its XX voltage when it really at X voltage and just needs more juice? And yes. I'm grasping at straws!

In that case maybe it is an electrical issue. The HDC board basically controls the heads so if there is a bad voltage regulator or something similar that could be the case. It's just weird that it works for a few hours and then starts to clog again.

If ink cross contaminated like you describe, that brings me back to pressure. Sometimes the pressure will be in range so it won't give you an error, but if it's fluctuating a lot it can cause issues. I'd check that just to be sure. It should fluctuate somewhat but not very far from it's base pressure.

Unfortunately this particular model is a little harder to diagnose without being there as well. There's just so much it could be!

 

[CN Spots]

I think that what the other operator was getting at. Like a it has a pin that's damaged or loose and only shows problems after it's been shook around for a few hours. On our previous JF1610 the ribbon cables had gotten damaged from being tossed around all day and had to be replaced. I made a bracket out of foam board with slots in it that cradled the cables preventing them from moving. Perhaps the newer machine has inherited this problem?

If you are referring to the pressure that is adjusted by those two small screws on the back left panel then yes, they adjusted that as well. It would bounce around between .5 and 1.0.

 

[CN Spots]

The tech replace the back flow preventers and flushed the system again. The clear head was cleaned and recovered all but about 8 nozzles. Those were mapped out and the voltage set to about 3/4 max. This resulted in us being able to print some clean swatches. After a few weeks it appears to be holding. The missing nozzles are still out but the number has not grown.

The plan now is to wait a few more weeks and monitor its progress. The tech will then return and lower the voltage to normal and see if that causes any more nozzles to drop. If it does not, he will install a new head (#4) and we'll blame all this on residual debris in the lines after the last back flow preventer was replaced.

 

[CN Spots]

Update: It does appear that it was the back flow preventers/debris causing the problem. It has been 2 weeks now on the newest head and all the nozzles are still firing. We have also implemented a maintenance procedure where we print a 3x3' swatch of clear every couple of days. I had seen this advised in other threads involving clogged clear nozzles that got little use. If anything changes, I'll report it. Hopefully this will help someone in the future.