Help! Need Mimaki JV4 advice.

[TBFL]

Hi All,
If anyone knows JV4 I have a situation for ya:
4 heads not firing, only the LC and LM on front and back are working. If the printer sits a while (hour or so) they fire great on a test. Run another test right after and I lose them. Clean does nothing. I have changed damper and I can draw ink through the capping station so I don't think ink is the problem. I know on paper this looks like an ink flow problem and I can't rule it out but it seems more electrical. Can cable or board issue be intermittent like this? Any thoughts? Thanks and any comments will be greatly appreciated.

 

[Andy D]

I know next to nothing about the Mimaki Jv4 but we have a JV34, and we were having a similar issue and called in a tech.
It ended up being one way valves (I think that's what he told us they were)
They are connected to the supply line, located right above the print heads.
He told us this was a known and common problem and they were pretty much useless,
so he removed them.

I posted a picture a while back in the Mimaki forum but can't seem to find it..

I just so happen to have the printhead cover removed, I will take a picture and post it when I get to work....

 

[WalkerP]

The JV4 doesn't have those valves mentioned before. Straight from cart>lines>dampers>heads>cap>pump>waste tank.

Make sure when you're doing a cleaning on those heads there is ink dripping into your waste tank. You may be able to pull ink from the bottom of the capping station, but the pumps may not be pulling hard enough.

Did you try changing dampers?

I don't think it's electrical.

 

[artbot]

place the LM and LC dampers over on your C and M channel and do the same test. if it starts working then you do have ink starvation or some kind of vacuum issue. if the same behavior
appears, then you are on to electrical. after that you are on to data swapping in order to rule out the slider board as the electrical cause of the issue.

 

[scrip]

there is a little L shape rubber in the pump that gets dry over time

causes the pump to do bizarre thing

 

[scrip]

look in the pump to see if that L is not broken

we used to have that small rubber part custom made for us
Cant find any at the moment

this place has a pump for 60$
http://www.robearle.com/parts/index.php

I do have a machine JV4 for sale

 

[TBFL]

Thanks guys!! I have replaced dampers no change. I don't see how it could be the pump since I can draw ink out from tube underneath capping station then immediately run a test. No print. Since the head has ink in it from the syringe draw I wouldn't think it's the pump. During a print how does the head get ink? From gravity? How do you get to the L shape rubber part in the pump? What electrical part would be most likely to short if say a cable was bad?
I appreciate all the comments!
Scrip, what size JV4 do you have?

 

[TBFL]

place the LM and LC dampers over on your C and M channel and do the same test. if it starts working then you do have ink starvation or some kind of vacuum issue. if the same behavior
appears, then you are on to electrical. after that you are on to data swapping in order to rule out the slider board as the electrical cause of the issue.

Artbot, when you say data swap do you mean switching data cables on the slider board with the known good channels?

 

[artbot]

yes.

 

[scrip]

Thanks guys!! I have replaced dampers no change. I don't see how it could be the pump since I can draw ink out from tube underneath capping station then immediately run a test. No print. Since the head has ink in it from the syringe draw I wouldn't think it's the pump. During a print how does the head get ink? From gravity? How do you get to the L shape rubber part in the pump? What electrical part would be most likely to short if say a cable was bad?
I appreciate all the comments!
Scrip, what size JV4 do you have?

have the JV4160
always used Epson inks in it
it has been sitting in the shop for a few month now

the L rubber part is inside the pump
its about 3/8H x 3/16W x 1/8D

 

[WalkerP]

"During a print how does the head get ink? From gravity?"

The ink initially gets to the head via the pump (or syringe as you have done). The ink line from the cart to the head has a vacuum in it. If X number of picoliters are fired through the head, theoretically if the vacuum is maintained, X number of picoliters will be pulled from the cart via that vacuum. If that vacuum is lost, which could be caused by a lot of things, you have to work to get it back. Gravity does have an effect too. If there's too much head pressure, you'll get dripping out of the head. If there's too little, you'll get starvation.

If the piezos aren't working or the nozzles are clogged, that's a different story. All of the advice on this thread is good. Swapping dampers and ribbon cables will tell you if it's physical or electrical.

 

[TBFL]

Thanks walker that helps me a lot. I never understood that part. I will try the data swap and let you know what I come up with.

 

[artbot]

not really how it works. the ink lines have light balanced positive pressure in them. if the negative pressure remained in the line, all the ink would drain to the tanks (which can happen if
you pull with a syringe from the waste line but forget to break that vacuum by pulling the carriage to the left for a few seconds). the positive pressure is much like a chain hanging off a roof.
if you hang one link off the roof, nothing happens, but at a certain number of links, the chain will begin to pull itself off the roof by the balance of weight on and off the roof under gravity.
ink acts as a fluid chain. the printer is balanced as if each fired picoliter of ink pulls another one into position inside the head.

 

[TBFL]

Ok did the data swap and got bad result perhaps i did it wrong. See attached. Any thoughts?

 

[TBFL]

Ok I have new info: if I reboot the machine it will fire all heads 1-2 tests then drop out. every time I reboot they will fire. Anyone ?

 

[APCInk]

It has been quite some time since I worked on a JV4, but I believe 4 heads are controlled by the main PCB and the other two are controlled by an HDC board. If I had to guess there was probably a short somewhere in the main PCB transistors that is causing none of the heads on that board to fire after one or two test prints, but I find it weird that it isn't throwing a head error of some kind. It could also be a short in the trailing cables or static buildup from overspray. As you can see in the photo of the slider board there is a lot of ink mist laying on the head cables. I would start by removing the slider board and using isopropyl alcohol to clean the slider board and connections at the slider. This would remove ink mist that could be causing a short across connections. Make sure you power off the machine and unplug it from the wall before disconnecting any of the cables. I would also use compressed air to blow off any remaining alcohol before reconnecting it to the machine.

Good luck!

 

[artbot]

i can't tell from the photo but it looks like the data swap isn't done properly. maybe it is. are you sure you know this procedure. it's dangerous to your printer if done wrong. the ribbons have to be moved in full pairs. the printer should not be able to recognize that the data (in full, not a half channel) has moved to a new head. and the overspray looks bad. i'm surprised that the printer works like that.

 

[WalkerP]

I agree with the last 2 statements. I would say it's electrical and I am too surprised the printer is printing at all. That thing is coated in ink!
Get it cleaned up and do the data cable swaps in pairs as artbot said. Make sure the cables are completely seated in the head(s) and board. Make sure the contacts are not bent, damaged or covered in ink.

 

[TBFL]

Thanks guys!! Much appreciation! I will start by cleaning off the slider board and re-seating the cables. I did not do the data swap correctly. I did not swap in pairs. Will keep you posted once I have the board cleaned. Have a great weekend everyone!

 

[Rotary Ryosuke]

Finale?

Did the issue still remain? I have a printer that is doing the same thing. I want to try and see if I can rule out what it could be before I send the slider board to get repaired.