Newbie CET flatbed "ink prime" question

[artbot]

i'm wanting to pull some new ink into the machine for a spot channel. if i unplug all the pumps that i don't want to pull/waste ink, leaving just the one single channel/pump plugged in, then hit the prime button will anything bad happen?

i know that there are check valves on all the pumps. i'm assuming that i'll lose a bit of ink in all the lines. i just don't want to toss so much ink pulling one line.

thanks!

 

[Letterbox Mike]

So you're wanting to basically shut off all channels but one, in essence, or am I misunderstanding what you're trying to do?

If that's right, I don't think it would cause an issue, but why no just close the ink valves above the heads on the secondary tanks, wouldn't that accomplish the same thing? Actually, it seems like you'd want to close those valves anyway, otherwise you'll be siphoning ink through the lines and through the heads anyway, I think.

 

[Letterbox Mike]

I re-read your post. I think I'm understanding you. Are you just trying to ink/prime one channel but the others are good? I so, yeah, just shut the valves on the secondary tanks on the channels you don't want to mess with and prime away, or just dial down the negative pressure to -2ish and let it drip until you're done. Doing that to one channel alone has no affect on the others if your valves are closed.

 

[artbot]

unfortunately, i'm away from the printer today. so the secondary tanks have a valve, open/closed, on them. that sounds easier accept would the pump be pressurizing the lines up to the secondary tank and when the valve gets turned to the "open" the pressure would cause the head to weep a good bit as it relieves itself through the tank? or with the "under/over filled" issue it will compensate?

the turn the negative pressure option has me a bit confused. do you mean close the valves but to the one channel i'm priming, then let the lack of negative pressure more gently ink run its course through the system?

also,
thanks for all the help! i have a lot to learn.

aa

 

[Django]

Pump will not pressurize the lines because the pumps only activate when ink level in the secondary ink tank is low. If the valves are in the off position, no ink will be consumed.

 

[Letterbox Mike]

Correct, when you close the valves on the secondary tanks the lines won't pressurize because there is no demand for additional ink.

On the head carriage, there should be a knob (brass probably) next to or near the negative pressure regulator/readout. The negative pressure should normally be around -3.5 or -3.7, but you can turn that knob to adjust it up or down. -3.5 to -3.7 is normal operating pressure, but turning it down to -2 or lower you're are effectively opening the vacuum system, allowing ink to flow constantly from the tank through the heads. It's the same thing as pressing and holding the purge button. When you're inking up, or when you have some air in the lines or stubborn clogged nozzles, this is an easier way to flow ink through the heads than sitting there pushing the purge button over and over. And you can do it on all channels or just ones that need it.

 

[Nameci]

@Artbot,

On a 6x10 there is no valve in between the secondary tank and the printhead that could isolate each head if you only wanted a certain head to be primed.

This feature is only present on the latest and some of the 4x8 CET with KM heads.

By pulling out the ink pump power connection, you are basically disabling the ink pumps. There is nothing bad that will happen physically to the heads other than you are going to empty out the secondary tanks that have the ink pumps disabled if you prime too long.

Since the delivery lines have check valves in between the pump and the secondary tank, the ink will still be present on the ink delivery lines up to the secondary tank. You will only loose the ink on the secondary tanks.

 

[Letterbox Mike]

My bad, disregard everything I just said, I didn't realize the 6x10s were different!

 

[artbot]

okay. lots of reading and a bit of understanding. i'll be at the printer monday (maybe tomorrow a bit). i'll definitely need to come up with a quick way to switch between ink types on a few heads that's not too wasteful.

one other newbie question. i'm assuming that there's no way to manually syringe pull ink with the printer off in a similar way that one might pull ink in a solvent machine. would the ink pumps not allow ink to be (gently) pulled through by drawing ink at the top of the channel before the y-splitter?