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MG Midget and Sprite Technical - MIG Misbehaving

Quite suddenly, when welding today the MIG began fusing the wire to the shroud and the wire feed tip.
Increasing wire speed didn't help other than to build up the unwanted pool of metal a bit faster.
Somethings gone awry, but what should I look for?
GuyW

If increasing the wire speed doesn't help, try increasing the distance between the torch and the work-piece.
Dave O'Neill 2

I don't think that's helping Dave. It's sparking between the wire and the shroud instead if the wire and the workpiece. Something changed, just not sure what!
GuyW

Have you looked at the tip and the shroud to see if there is anything there that shouldn't be? Something might have gotten stuck there that is causing the problem. Or the shroud might have come loose a bit (if it's threaded on) causing misalignment.
Martin

Neither of those things, Martian. WHen it first happened it had fused itself to the tip so solidly I couldn't unscrew the shroud to get the tip off. Had to dismantly the gun to get it apart and reassemble with new tip and clean shroud, All looked fine there.

I was welding outside in the cold so not inclined to investigate further. But now I am indoors I wonder whether the problem was with the earthing of the workpiece so it was earthing to the next best thing - the shroud. The earth clamp was secure but I didn't check back down the cable or conections back to the unit.
GuyW

My MIGs been doing something similar lately but I think it may be a "sticky" wire feed whereby the wire stops momentarily and welds to the tip. I've removed tip and shroud countless times to clean it up but I think the torch liner is worn and needs changing - easy on a Euro torch but I don't know about non-Euro ones. Also wire feed may be sticking off the spool or through the feeder.
Bill Bretherton

While I don't think this will solve your problem Guy, I use an anti splatter spray and squirt a little up the nose of the gun and it helps to stop build ups sticking to the tip/shroud.
I think it is a 'Murex' ? product (BOC) came in a lever action squirty bottle.

Similar to this stuff :-

https://www.wellyweld.com/products/Antispatter-Binzel-Protec-500ml-45095.aspx
richard b

Guy,
Your shroud should be insulated from the main body of the gun and therefore unable to spark to it.

If it's arching to the shroud there must be a breakdown in the insulation somewhere. Have a good investigate looking for bits of weld or damage at the back end where it attaches to the gun. I sometimes get a bit of weld at the bottom of the shroud that bridges the fibreglass insulating ring.

Best of...
MGmike


M McAndrew

I have some Murex anti spatter spray but never found it to work very well so it tends not to get used, for the tip and shroud I use Tip Dip like https://www.ebay.co.uk/itm/SIF-Anti-Spatter-Tip-Dip-Gel-Paste-500g/220441224989 . That's just one make, various others make/sell similar stuff.
David Billington

Clearly needs investigation.
The pertinent thing is that this started to happen quite suddenly. I have done a lot of welding over the years and this particular set up has been in use for the last 2 years at least, and with no problems. Something has changed. Its not weld build up inside the shroud because I fitted a new tip and shroud when it first arc'd but that didn't cure it.

I think it is going to be either intermittent wire feed (variable speed) as Bill suggested, or inadequate earthing to the work piece.
GuyW

Are you gas or gasless wire Guy
William Revit

Gas. Argon/CO2
0.6 wire
The only other thing, it was pretty cold and damp. Not raining but one of those still days when any cold surface gets a coating of condensation. I wonder if that maybe was causing the rollers to slip on the wire.
GuyW

I'd say you are on the right track.

From personal experience a few times, it's a wire feed problem. When the wire feeds too slowly for the current, it fuses to the tip.

To check. Pinch wire between finger and thumb. If you can stop the wire easily, and the feed motor doesn't slow down, then it's likely the pinch rollers or the liner. If you can slow the motor easily, you may need another motor, but that is less likely.

The rollers can be dirty or worn, (could be moisture, try cleaning and increase the pressure). The top is flat and the bottom, driven by the motor is grooved, .6mm and .8mm. Inspect the top roller for a 'wear' groove. You can buy them (it's just a small bearing), or you can just reverse it on it's spindle, thus presenting a fresh surface to align with the groove in the bottom roller. Make sure the bottom roller is clean.

The other likely problem is the liner. If plastic, eventually they get damaged by debris carried through by the wire. Change it for a metal liner.

As I say, personal experience, and the first signs are suddenly blobby welding, followed by wire constantly fusing to the tip. New tip solves it for a very short while, and then it begins again.

anamnesis

P.S. Mine's a Clarke but I would think the same issues apply to other makes.
anamnesis

There is new scientific evidence from the International Agency for Research on Cancer that exposure to mild steel welding fume can cause lung cancer and possibly kidney cancer in humans. The Workplace Health Expert Committee has endorsed the reclassification of mild steel welding fume as a human carcinogen.
Alan Anstead

Doesn't surprise me at all. I often get an irritated throat and a bit wheezy if fumes get under my mask. Hard to avoid unless outside or with an air fed mask I guess.

Does that research apply to occassional/ammateur, or just full time pro useage?
anamnesis

This thread was discussed between 01/12/2020 and 03/12/2020

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