VJ 1614E - Magenta problem - diminishing AFTER printing

[FaneDuru]

We use such a machine since 2011 and it worked well. Last year we faced a problem regarding black side of the head and it was obviously for everybody that the had is gone. But I found a way to transform any CMYK layout in CMY, using a specific color profile and the layout transformation is not visible for anybody. So even using a little more ink we could print well using this workaround and the old head...
Now I am facing the next problem: The Magenta side started to behave strange. I mean there are the next thinks looking strange:
1. After a good cleaning it works well. Printing let's say 1 meter length (about 1 meter width) it works perfect. After stopping the machine if I start it again with the same layout it prints wrong... Like some vacuum is created during printing and stopping the machine air is absorbed into the printing head.
2. If I start printing three such layouts it may be working well or at the end Magenta ink starts to diminish.

About two weeks before Magenta ink tank has not been filled on time (bulk ink system) and some air went into the printer sub-tank. I knew that small air quantity is not so dangerous and I printed well for a while. Now I remember that story and I thought that maybe that air can explain the above described behavior and I proposed myself to extract it. So, with printing machine Off I took out the Magenta damper and using a syringe and a Y tube I extracted all magenta ink and finally some air appeared.
But keeping air sucking a kind of vacuum has been created and removing the syringe even more air went inside the pipes... Ideal would be to open that specific sub-tank valve in that moment of having the syringe creating vacuum, in order to absorb all the air on the pipes, but HOW TO DO THAT? If I try the above described operation with machine powered On, when its sub-tank will be emptied the valve is automatically open and the air still remains on top of the ink. I need to open it only when the sub-tank is fully emptied. If I would try to power On the machine it will try to move the carriage to the cleaning station...
Is there a workaround or another idea to be used in such a situation?

Thanks in advance!

 

[FaneDuru]

I fount a way to take out the air. There is an option in Self-Diagnosis Mode to close and open the valve when you need...

 

[ewded]

Just repeat the process used with the black ink and update the profile and use CY instead of CMYK you should be fine.

 

[FaneDuru]

Very clever...
Usually when you want to loose time it's good you just sleep. We will not be informed about your tiredness.
I tried thinking and finding solutions based on logic. That process is difficult indeed and not accessible to anyone...

 

[ewded]

Black is gone, magenta is not working perfectly, maybe if you don't want to go below everyone on the market by selling 3 euro/sqm banners you could afford a new printhead every 6-8 years.

 

[FaneDuru]

Yes, we can. That machine head has been changed three years before.
But we have other machines in good condition fully loaded and why not keeping it like spare and using it in order to explore its possibilities? It is not loaded and we can afford playing with it in let's say didactic way. We usually print on it selected layouts not containing much of black. Sometimes was a good and necessary backup also for black background layouts. Don't you like to understand why thinks are happening in a specific way? If not, this is your choice and I do not care too much about that. I always use the knowledge obtained doing analyzing and just trying to understand...
Don't you like to have an explanation about what happens in the machine head after perfectly continuous printing and completely wrong after just stopping it? If not, again it's your choice. But let me try to understand, please...

 

[FaneDuru]

Finally I solved the head! I unclogged it completely...
I will briefly try to explain what I did, but just for people daring to do it.
Firstly the method is good to be applied just for a head not offering perfect nozzle check but the appearance of consecutive checks is different. I mean if one side of Magenta is not complete but each time the problematic nozzle is in a different position. Meaning that the head itself has all nozzles open but the head FILTER for that area is clogged and not enough ink can reach to fill all the nozzles.
The head assemble is made up by two separate pieces: the head itself and the plastic part connecting the dampers to the appropriate ink area of the head. That last plastic part contains very fine filters, one for each of the 8 ink zones. When your head assemble has the above described behavior this means that the filter of that specific area is clogged.
So, I did the next operations in order to make it usable again:
1. I took out the dampers and put each of them in a small plastic bag, hanging on the ink pipe;
2. I moved the head carriage in the left maintenance place and using a syringe I spread cleaning fluid through the head until each ink color disappeared. Very important: I used the same syringe in order to blow air until all the ink has been removed. This is important in the moment of dismantling when is not good to have any liquid on the head electronic board...
3. I removed the head assemble from the carriage. I wiped it very well. I also removed the small pipes connecting the dampers to the plastic part;
4. I dismantled the head assemble. Both pieces are kept together by three screws keeping also the metallic frame around the head. I kept the head side having the connection socket on the top in order to avoid an eventual leak on that sensitive area ;
4 bis. I put the head on a piece of lint-free cloth, well spread with cleaner in a small canon lid and I wrapped all that with stretch foil. I did that in order to avoid the ink drying on the period I will do something with the filter of the plastic side;
5. I used a small Chinese digital ultrasonic cleaner bath (We use it in order to clean the oxides from the electronic boards) and firstly I used isopropyl alcohol. I immersed the plastic part with the side towards dampers on the top. The alcohol level was enough to cover the device. I started the ultrasonic cleaner and from time to time I pulled alcohol using a 60 ml syringe. I firstly pulled in order to eliminate the clogged material on the opposite flow direction. After a while I started to push the alcohol in its normal flow direction. I did that for about ten to fifteen minutes. Because of the ultrasonic waves the alcohol became warm;
5. I removed the isopropyl alcohol, cleaned the bath and started to use Cleaner (WO 131). I must confess I do not know if the previous phase (using isopropyl alcohol) was really helpful but I describe here as exactly as I remember what I done... After starting the ultrasonic cleaner each small piece of dried ink started to be dissolved and passed into solution in some minutes. I repeated the 'syringe operation' (pull and push) for about 10 minutes. The cleaner became black and I change it with a fresh clean one. I did that three times until the cleaner remained almost clean (a very little gray, but without any visible particles...). I consumed 550 ml cleaner. I tried to use a pump (vibration pump) which worked well until the solution became worm. After that the liquid alcohol started to be transformed in gases inside the pump and it did not work any more (cavitation fenomena). I could find another type of pump but I estimated that what I did was enough. I could do that estimation based on the next fact: Initially the difference in force to pull the syringe handle was obviously bigger in case of problematic areas (Magenta and Black) in comparison to the rest of ink areas. After all that operation I couldn't feel any difference or a very small one...
6. Finally I pulled some clean cleaner through all ink areas in order to eliminate any small part of dried ink;
7. I wiped both pieces very well (print head and plastic side), I blew them with hot air and assembled them paying attention not to force too much the tightening screws.
8. I mounted the print head assemble on the machine, cleaned it in three cycles and it works like a new one.

Epilogue: This job is for patient people wanting to try in case of having some spare machines working well or the workshop is not too loaded.
It works only for the case of bad nozzle check on a specific area but HOLES NOT IN THE SAME POSITION for consecutive nozzle check.
I do not have any idea about how much time the head in discussion will work well...