Mimaki JV33 head starving problem with bulk system ....

[rofo]

We have Mimaki JV33 running with bulk system (refillable cartridges with floater inside to keep constant ink level) and for a long time we have a problem with head starving. We did a lot of thing to find out what´s the reasone for this issue, anyway nothing helped.
For your information printer is having new head, dampers, capping station and pump. It is running in 2 x CMYK and we made also "tuning" as each position has its own tube leading directly to the cartridge. All 8 cartridges are used at the same time, electromagnetic valves are bypassed.
The problem is the we still have random dropouts during printing. In one pass we loose one position on the head completely, no one nozzle remain. One normal cleaning is enough to print again. It happens randomly after some time as well as it happens on a random position of the head (MCYKKYCM). Some positions are more sensitive than the others. For example, during the week left magenta do that once only but the right one eight times.
Any idea what´s the reason for this issue?

 

[Robert M]

Gravity

Any way to adjust where the carts are in relationship to the print head. Moving the bulk system up and down can change the way the ink flows to the heads.

 

[rexsee]

i have the same problem before, and it's still a problem now, although specifically in a yellow ink

I have the original thread here
http://www.signs101.com/forums/showthread.php?p=723489

artbot has and other people has discussed this in detail, hope it helps

 

[Stan B]

heat and humidity? (I was suggested that)

 

[rofo]

To Robert M.: Bulk system has floater inside the cartridge, but it doesn´t change anything as we tried to change ink level step by step from minimum to maximum. Also different bulk system was tried where the cartridge is used only as an extension to the ink bottles so the ink level is let´s say 20cm higher than in the cartridge but the problem is still the same ....

To Rexsee: Thanks, I´ve read it before but I didn´t find a solution and you moved the thread subject to white ink, so I´ve tried it again.....

To Stan B.: I don´t think so. Temperature is about 20-25°C, doesn´t matter if it is summer or winter, sunny or raining. Mutoh Spitfire staying 1,5m far away from Mimaki printing with the same ink is working perfect without any problem in a same conditions ...

 

[Stan B]

I'll tell you this. We have 4 JV33 in the same room, 2 older ones and 2 brand new ones (one is sitting and 3 are printing)

and we expirience similar problems as you are. Color will randomly drop out every 10-15 feet on random channel on all three printers. The fact that it is happening to all 3 printers at the same time, regardless of firmware and printer age, suggest that it is an outside force, or the ink it self, casing the problem.

I personally think that with summer and being too hot viscocity of the ink changed and heads are drying too fast because ink is not as liquid as it should \ drying too fast.

 

[rofo]

There must be a a reason why does it happens and I will find it As the channel stops the printing in a second it can´t be drying. It is not like a drop out when you loose the channel continuously during 10 centimeters. Summer, winter, hot, cold, rainy, sunny - I really didn´t find any correlation between drop outs and described conditions.

 

[artbot]

if the ink chemistry is an issue, you could add a tiny percentage of butyl carbitol to the ink and it will incrementally alter the dry time without affecting the opacity whatsoever. such as over a liter of ink, add a 1/2 teaspoon of butyl carbitol. this solvent has the cutting ability of watered down alcohol. and takes eons to dry. so add carefully. i developed a clear varnish for my 160sp the other day and it required almost 1:1, carbitol to cellosolve. that tells me that triangle already has a lot of carbitol to the mix to achieve the match. carbitol is already in the mimaki ink, it's just a matter of adding a little more.

i'm not saying that this will solve the drop out issue. but if dry time in hot weather as stanb mentioned is suspect, then there's only one way to fix that. fix the ink.

 

[Rooster]

Perhaps the maintenance settings could be changed to have the printer perform more self-cleaning cycles?

When these drop-outs occur is it during a point in the run where that ink hasn't been in use or does it happen even if that channel has been printing fine up to that point in the print?

 

[rofo]

To Artbot: This is not about the ink chemistry. Or let´s say that your idea will not help in our case. For example left magenta channel had no drop out during two weeks, the right one did it maybe 15 times in two weeks. Same ink, same ink level, same conditions, same consumption on both channels. One is running OK, second not ...
To Rooster: channel is printing fine up to the point of dropout. And if it possible color stripe on side of print is used on every job ...

 

[Stan B]

sabotage?

 

[artbot]

i'd just start diagnosing the starvation. first off when you do the cycle, instead, pull the damper to get a better feel of the resistance inside the tube during the failure, when the failure occurs, is the ink receding in the line? or is the damper full as always, when you look at the damper, is the membrane concave or relaxed? i once had a horrible starvation problem the only way it cleared up was flushing the ink tubes in reverse (pushing cleaning fluid backward into the carts. maybe there was a little chip/clot of cartridge rubber or something in the piercing nipple??? i'll never know, but it was gone in a minute after a lot of headaches.

 

[rexsee]

ArtoBot: Since you mentioned adding butyl carbitol in the ink itself, I have a question, I have been experiencin problems with the black ink, and the tech itself suspects the black ink has a problem, well, meaning their ink itself, every now and then I get clogging heads on the black ink that needs to be flushed which is very costly, the suspect is the black ink BS2 is too strong for the head, do you think adding butyl carbitol would help?, btw, I have changed printhead (under warranty) twice already in one month, and that is because of clogging in the black which comes to a point where it cant be removed.

 

[artbot]

it certainly would be worth a try. i recently switched from SS2 to triangle. i did some dry tests before installing. from what i could tell the triangle dried a bit slower. i figured whatever. as soon as i got the ink in the machine, i went to the usual cleaning routine. with the SS2 i would commonly go to the cleaning station on the far left and clean off these little rings of ink (in the shape of the cap) from the bottom of the cap. keep in mind, i don't print very often (at least color) mostly solvent clears and whites, almond, soon silver, and uv clear from the special channel, etc. but that slight difference in dry time changed the maintenance of the printer. it now runs cleaner because of the slightly slowed dry time.

if you play around with the idea, buytl carbitol is odd stuff. once i mixed it too high in a two part urethane and the urethane would hardly dry under a torch. it can render a resin "un-dry-able".

you could either try switching the black to triangle only? or doing some testing, print some stock black patterns and some colors that require black. then mix up a small batch of custom black, with about 5% carbitol added. see if the print is a mess or fine, etc. also, a little trick, when i develop a new ink, i don't put it in the printer right away, i brush on very tiny crosshatch patterns on my substrate, and also put it in a mini-jet to to some quick tests. check for crawling, and always put the factory ink right next to it to visually match the viscosity and evaporation time.

 

[rexsee]

sorry artbot, what do you mean traingle?

it certainly would be worth a try. i recently switched from SS2 to triangle. i did some dry tests before installing. from what i could tell the triangle dried a bit slower. i figured whatever. as soon as i got the ink in the machine, i went to the usual cleaning routine. with the SS2 i would commonly go to the cleaning station on the far left and clean off these little rings of ink (in the shape of the cap) from the bottom of the cap. keep in mind, i don't print very often (at least color) mostly solvent clears and whites, almond, soon silver, and uv clear from the special channel, etc. but that slight difference in dry time changed the maintenance of the printer. it now runs cleaner because of the slightly slowed dry time.

if you play around with the idea, buytl carbitol is odd stuff. once i mixed it too high in a two part urethane and the urethane would hardly dry under a torch. it can render a resin "un-dry-able".

you could either try switching the black to triangle only? or doing some testing, print some stock black patterns and some colors that require black. then mix up a small batch of custom black, with about 5% carbitol added. see if the print is a mess or fine, etc. also, a little trick, when i develop a new ink, i don't put it in the printer right away, i brush on very tiny crosshatch patterns on my substrate, and also put it in a mini-jet to to some quick tests. check for crawling, and always put the factory ink right next to it to visually match the viscosity and evaporation time.

 

[artbot]

triangle ink

 

[rofo]

To Artbot: I´ve focused to the same idea. Dampers, ink tubes, nipple. As the ink is working perfect in Mutoh ValueJet which is using the same head I think the ink is OK. What´s the difference between ValueJet and JV33 is the ink system as JV33 has cartridges placed higher than the VJ and different type of dampers are used. As the issue we are experiencing with happens from the beginning I don´t think so there is problem with tubes or nipple but it is easy to flush tubes in reverse. Next thing we are trying is that we have a list of dropouts with dates and time for each channel. I´d like to exchange the damper on every channel which will be the most sensitive for dropouts. Dampers remains always full even in case of dropout. It is hard to see if it is relaxed or concave when it is seated on the head. My personal feeling is that when you manually suck the ink with the syringe through the damper some membranes are working better than the other. The other fact is that we are using 3rd party dampers but the issue happend from the beginning with the original dampers also ...

BTW: When you are talking about Triangle inks I´ve seen results and it is not the best choice you can do... My personal feeling only ....

 

[Stan B]

what about print mode \ speed? If it starves \ drop out in the fastest mode, did you try slower higher res print modes? Mostly all our ink troubles go away with a slower print mode but we can't afford it. Maybe mutoh has "thicker" ink lines and JV33 thinner so it simply can not get enough ink to print that fast?

 

[rofo]

540 x 1080 6 pass. Nothing special, nothing extra speed. With slower print mode you can reduce the troubles but in this case you are not able to make some money if you will print 4sqm/h ....

 

[artbot]

and you've adjusted the height of the ink supply. i've got my white cartridges mounted outside the machine and just raising them a 1/2" drastically affects the siphon. you can starve them or have them sweating white ink with minute adjustments.

remember that these inks are not under vacuum inside the lines. when you put your finger on top of a straw and pull fluid, the fluid is not under vacuum but it is held there by the positive fluid tension pressing against the inside of the straw not allowing the air to displace. the printer is just like that straw, your ink lines are that straw laying on its side. the way for the ink to escape is at the print head, thus raising the supply raises the fluid pressure inside the lines increasing it's ability to fall out. think of it as a chain sitting on the edge of a roof with a few feet dangling. and raising the cartridges is like increasing the incline of the roof making it easier for the dangling end to pull the remaining chain off the roof.

so concaved dampers are not good. it says that there is a resistant force pulling at the other end of the ink supply. the "chain" is nailed to the roof at the supply end.