Outdoor Junior Printing Problem

[Rat_Fink]

Hello...
I have a Mutoh Outdoor Junior 36" Printer.

I have had a problem for the past couple months when the printer sits idle even for just a few minutes - it seems as if the Black & Magenta colors need to be "primed".

When I start to print - the magenta starts off really dark & then starts to print correctly. Once it starts printing correctly - it keeps printing fine till the print is done & it sits idle again.

The Cyan & Yellow lines do not seem to have this problem & the Black is not as bad as the Magenta.

It also seems as I have a banding issue that I did not have in the past - not sure if these are related or not. I tried the banding adjustment with no success.

The print heads, maint stat. & pump are fairly new.

I attached a pic to show what happens when I print a Magenta sample.

Thanks!

 

[Finishline Signs]

Mine did that a couple times, never did figure out what caused it. I ended up changing the heads about a month later and it hasn't done it since. Don't know if that had anything to do with it.

 

[Jackpine]

Generally a cleaning will fix that. I think environmental conditions have caused stranger results. I keep the temp and humidity in the print room in the normal range on our gauge. I would clean the cap station and the head and do a normal cleaning to start.

 

[Rat_Fink]

Thanks for the info...
I have run it thru many many cleanings (normal & powerful). Perhaps a head wash would help. Also - could this be a problem with the dampers?

Thanks
Mike

 

[CS-SignSupply]

Looks like an ink starvation issue that could be caused by low flow through the dampers.

Head cleans and washes may not resolve the issue. Replacement of dampers is probably a must.

 

[The Big Squeegee]

I'll second the dampers but not for the same reason...

The dampers are one way valves. If they loose the ability to keep the ink flowing toward the head only, then it will siphon back to the carts. This could be a slow leak. The mixing of colors indicate that the ink is flowing into the head from the cleaning station.

 

[CS-SignSupply]

I have seen on several occasions where ink from one line had siphoned into another through the cleaning station. If the damper was a one way valve, this would not be possible. If the cleaning station is saturated and one cartridge is 20% full and another 90% full, it is possible for the vacuum pressure to equalize to a 50/50 level, and allow ink to traverse back through the the cleaning station into a different ink color line. This usually means the printer has sit for a long time without any use.

The reason I think it is a starvation issue is that the damper may be slightly clogged and allow a slow flow of ink to the printhead, which is depleted rather quickly. If you were to wait 10 or 15 minutes and send the same print again, it should do the same thing.

Of course I may be wrong and either way, changing the dampers will probably fix your problem.

 

[The Big Squeegee]

I have seen on several occasions where ink from one line had siphoned into another through the cleaning station. If the damper was a one way valve, this would not be possible. ...

I have worked with dampers a bit. If I remove the damper from the head the supply ink does not drain back. If I loosen the fitting on the damper and let air in, the ink will drain back toward the carts. If the damper looses its ability to hold the ink from going back into the carts then it has lost its ability to be a one way valve.

 

[CS-SignSupply]

See your point and have run into that but you can connect a syringe with tube to each side of damper and push/pull ink through. Obviously don't recommend this but have done before.

Again, no issues here if I am wrong. Nice to share thoughts and experiences.

 

[Rat_Fink]

Thanks for the info - I'm going to switch the dampers to see.
Adding to what you are saying...
If the printer sits all night the first print will be messed up for prob close to ¾" - to 1". If I let it set for a few minutes & start another print - the beginning of the print will be messed up for the 1st ¼" or so.

It appears that once I have a steady ink flo - I'm OK, but once it sits for even just five minutes, the problem will come back a little.

I have just been printing a solid band of color before each run to get the inks flowing because I did not have time to mess with it.

I'll post the results once the dampers arrive & are installed.

Thanks
Mike

 

[P Wagner]

I would also replace the capping/ maintenance station if it's been more than 6 months since it was replaced. Sponges have a tendency to swell on the FO's and can cause cross contamination that you're seeing.

Bob

 

[bartman]

sorry, what did you find out after changing dampers?