[choprboy]

Long time Jody watcher, first time poster... I am a self-taught hobbiest welder, to date mostly doing stick and a bit ofTIG on a bunch of different projects, but I need a bit of MIG practical knowledge help.

I recently picked up an old Miller Challenger MIG welder to learn that side of the equation. It was rather beat up, but the price was right and came with a full 15# owner CO2 bottle. I completely cleaned out the unit, replaced the original burnt-out M15 gun with a new M150 gun, replaced the factory 8awg ground with a new Dinse-connected 4awg, replaced the power cord, etc, etc...

I fired the rehabed Challenger up and can weld with it, but the arc is sporadic. At times I can lay down several inches of bead no problem with a nice continuous buzz, at other times there are lots of pops and arc starts/stops as the wire hits the work and then blows out. To keep any semblance of a continuous arc I have to keep the tip what seems like an extremely close distance (like less than half the diameter of the nozzle), so I can;t see what I am doing. Is this normal?

I think a large portion of the problem might be my gas flow, but I don't have MIG experience on what to expect. With the Challenger I have a large blast of CO2 when I first pull the trigger, but then seems like there is very little gas flow afterwards. My regulator is a new generic Victor argon/CO2 kit, set to 20CFH. My only comparison is to my Syncrowave where 15CFH of argon while TIGing seems to be more flow, but I don;t have a practical way to measure it.

Any other ideas on what I should be looking at? I am currently trying to decide between investing in a quality CO2-only regulator and swapping my nearly full CO2 bottle for C25 at the LWS.


Adrian

[gamble]

If it's straight CO2 which is what it sounds like it could be freezing up your regulator. Get a tank of c25 and see what happens.
Also wouldn't be a bad idea to open up the case, blow it out with compressed air and tighten all the lugs and terminals in there.

[choprboy]

I completely disassembled/blew out the case, undid/checked/re-tightened all the lugs, and replaced a couple wires/lugs when I rehabbed the welder. But my regulator is frosting up and spitting little bits of CO2 pellets after a bit of use. From what I have read, combo argon/CO2 regulators may have problems on straight CO2, so I wasn't sure what to expect. I just got back from the LWS and they suggested that maybe I have a CO2 tank with a siphon, drawing liquid straight into the regulator.


Adrian

[Otto Nobedder]

The C25 will be a big help, especially if you have a siphon in your CO2 tank (quick test, turn the tank over, and see if it improves... CO2 does "decent" welds when it's working right). If your regulator get frosty or very sweaty when used upright, that's a good hint. Any good regulator will "sweat" a bit with heavy use, but at 20 CFH, it should take a bit.

CFH for MIG should be closer to 35.

Even with the new ground wire, the clamp may be giving you issues. Grind your ground point clean, and clamp some copper-wool (from the cleaning/dishwashing section of your supermarket) between your ground-clamp and the workpiece, and see if that improves things. If so, Jody has a video with a fix.

Just some thoughts.

Steve S

[choprboy]

Yep, been thru the ground a couple times moving it around and cleaning. New Tweco bronze pincer-type clamp with the new ground cable.

My gauge only goes to 20CFH on CO2 so.... With the regulator hose wide open at 20CFH it will run about 70-90sec before the needle starts to get erratic and it makes gurguling noises/spits CO2. Tried my other regulator same result. I also already tried the tank valve wide open upright and inverted, plume of white CO2 either way so a bit inconclusive. I haven;t tried welding with it inverted yet.

It's about 108 out today. With the tank and regulator sitting in the sun it seems to be doing much better than last night, though I have been doing much shorter/intermittent welds as I'm grinding/finishing the previous welds. So I may be on to something.

[noddybrian]

OK - a couple of thoughts on this - if I'm way off the mark don't laugh - I'm not familiar with cylinders from across the pond - but 1st up - if it was in the UK very few CO2 cylinder are made with siphon tubes as it is not common to want liquid discharge for general use - only time I've seen them was for deluge fire systems ( mostly boat engine compartments - some computer rooms after halon was banned ) if this was the case the cylinder will usually have mounting orientation marked on the neck & the fire system maker ( such as Chubb ) + some coded stuff - if there is no mark like this assume it's a standard bottle - again in the UK around the neck would be some stamped info such as working pressure / test pressure etc - amongst this should be a cylinder weight empty & the designed fill weight - with CO2 there needs to be sufficient space to allow evaporation of the liquid to gas ( much like propane etc ) is it possible your cylinder is just over filled & has insufficient evaporation space - a quick weigh on the bathroom scales should confirm this one way or the other - if this is not the problem lets ask about the regulator - over here it is normal to use an adjustable pressure regulator & fix a flow meter / needle valve to it - to avoid gas wastage we set the minimum pressure possible to achieve a consistent flow - but in various posts here I see the use of these retarded flow gauge style regulators where only the needle valve is adjustable to achieve desired flow - the pressure is fixed - often high enough to use the dam thing as a cutting gauge like 40 > 60 PSI - now if you repeatedly pull the trigger on the Mig & dump 60 PSI in bursts with a nearly full cylinder I could imagine creating problems ( there has been at least one post on best practice to reduce gas surge wastage especially on Tig welders ) - more so if you do not have a heater - I've seen plenty of hobbyists use CO2 without heat for auto body repair & other non critical jobs - but long ago when I was in college I was told CO2 created various welding issues unless pre-heated - I have used it on occasion but I still have an old ( like probably 60's maybe 70's ! ) BOC pre-heater - this screws to the cylinder then the standard regulator screws to that - nowadays you can get a single heated regulator unit - in my opinion well worth it - weld defects aside the gas volume alters dramatically with temperature & by pre-heating - your cylinder will last way longer - although I don't like or use CO2 of choice there are odd times I will & you can get an acceptable looking weld - yes Argon mix is neater & more forgiving on machine settings - but you should get the machine to run with plain CO2 - much as Jodie demonstrated recently - OK enough with gas discussion - maybe Otto or Braehill will chime in as they are far better qualified to comment - I have at best a laymans knowledge + years of learning by mistake !

On the intermittent power issue unfortunately it could be a variety of places including machine contactor / voltage selector switch / main transformer tails / inductance coil / rectifier / power leads to earth connector / gun / hose assembly - only advice really is undo them all one at a time ( to avoid mixing anything up ) clean them & re-tighten - now try the machine turned right up - get someone else to weld while you watch - look carefully for any spark / heat haze or smoke indicating a hot spot - cheap infrared thermometers often find hot spots - if nothing is obvious - unplug the machine after welding for a few minutes & touch all the major components - it will obviously get warm - but is any part much hotter - still nothing ? watch the wire drive while someone else welds - is it erratic ? if so it could be as simple as a dirty potentiometer track giving varied wire speed - or a bad liner / torch / contact tip - hope some of my rambling makes sense or helps - sorry I can't be more specific as I don't see your machine over here.