Miller dimension NT450

[angrybird61]

Hi everyone, I'm new here and have done a search with no results, so now I'm asking for your help. At work we have a Dimension NT450 as stated in the title. The shielding gas stops coming out after about 3 seconds of welding, when on the mig setting. The cylinder is full and the regulator is set to about 25 or so cfm. We are in an enclosed shop so wind is not an issue. The ball inside the flowmeter completely drops and the weld becomes very porous after a few seconds after holding the trigger? Is there a gas solenoid inside the machine that may be causing this problem? Any help would be appreciated. Thanks in advance.

[H80N]

Maybe a piece of lint/crud/fluff between the gas bottle and the regulator..... not uncommon if somebody was a little sloppy when they changed out the bottle

[ryanjones2150]

can you hear the solinoid clicking on and off? Surely that machine has one.

[angrybird61]

I'll have to listen for a solenoid tomorrow. I can hold down the trigger for about 3 secs before gas stops flowing. I can count how long it takes gas to stop and it's the exact same amount of time each time. At first I thought there was a sensor of some sort that would stop the gas from flowing if there was no arc. A coworker noticed it when he was messing with wire speed. But we started running beads, and the gas stops flowing while welding too.

[H80N]

I'll have to listen for a solenoid tomorrow. I can hold down the trigger for about 3 secs before gas stops flowing. I can count how long it takes gas to stop and it's the exact same amount of time each time. At first I thought there was a sensor of some sort that would stop the gas from flowing if there was no arc. A coworker noticed it when he was messing with wire speed. But we started running beads, and the gas stops flowing while welding too.

Was not kidding about the possibility of crud... that is why you are supposed to crack the tank valve for a moment to blow out any debris that may have deposited in transport...before reconnecting the regulator...
...........the described symptoms would fit

Maybe a piece of lint/crud/fluff between the gas bottle and the regulator..... not uncommon if somebody was a little sloppy when they changed out the bottle

[ryanjones2150]

I'm kind of paranoid about getting crap in the lines. Even if I disconnect the fitting end from the machine, I purge the lines before I reconnect them.

[H80N]

I'm kind of paranoid about getting crap in the lines. Even if I disconnect the fitting end from the machine, I purge the lines before I reconnect them.

I have been bitten a few times over the years... a victim of my own brainfade or laziness.... where I forgot to crack the valve to blow out debris....
and drove a slug of crud into the regulator...

https://www.youtube.com/watch?v=x4Aoanbe0NI

Some of the newer regulators have a sintered bronze filter in the nipple to prevent this type of damage

[digr]

Take the hose off the reg and turn on the gas and see if you get flow if so take the hose off at the machine and try again, at least you will isolate the problam

[angrybird61]

I checked for debris, there was none. I also unscrewed the hose from machine and it does get uninterrupted flow. I did notice a clicking from inside the machine when the flow stops. Sounds like a relay or solenoid. An airgas rep is gonna pick up the machine and check it for us. Our boss doesn't want us to open it up for warranty reasons.

[ryanjones2150]

Ah cmon! Tell your boss to grow a pair! He's no fun.

[angrybird61]

Yeah that's what I said. Lol. His response was," it wasn't your 8000 dollars for the machine". My rebuttal was "it wasn't yours either". He walked away a little angry.

[ryanjones2150]

Probably be an easy fix for the tech guys anyway.

[cruizer]

There is crud (likely teflon tape) in the feeder screen where the gas comes in. Quite common.