Mig Welder Caught Fire

A bit late, but. . . Where studs run through plastic/tufnol/.. bushes the nuts that clamp the connections should not rely on the compressibility of the bush for a good connection. i.e. fix one wire on with a pair of nuts, then lock the stud in place with another nut, then finally with another pair of nuts lock the wire on the other end of the stud. This way if the stud runs warm and the plastic starts to deform, the electrical connection remains OK even if the whole thing gets a bit floppy.

Frank

Thanks to all for the replies. Like a lot of chinese stuff its a design fault or shortcut, in that the brass bolt carries the full welding current and gets hot, plastic sleeve melts, bolt shorts on bulkhead, plastic insulation catches fire!!! Its fixed now.

Regards

Dave Tointon

Just a thought - but if the fitting/insulation got so hot it caught fire is the wire/fitting sized correctly? Could be undersized perhaps? Manufacturer trying to save money. Not unknown!

Here in the UK the weather is rubbish one day, and cr*p the next. Just thought I'd mention it, not at all envious of you Aussies.

Chris

Edited By ChrisH on 04/03/2012 12:43:46

Slighty OT story to brighten an otherwise dull day but still MiG related.

Many many moons ago I bought a Migatronic MiG welder of 200 amps capacity, lovery machine only marred by the fact it used a propiatary torch which after an accident being run over got changed to a standard Binzle torch.

Now this machine was used commercially and it did some serious work, no idea how many 15kg reels of wire went thru this machine but probably geater than 60 -70 ?

So one day it died, horrible gurgle, smoke and lay on it's back ith it's little tiny feet in the air, heart breaking to watch. So went in for repair and the rectifier bank had died, new bank fitted and new lease of life.

Fast forward another year and same happened, went in S/H unit fitted as there were no spares now for this and back out again. Later same happens again.

Sounds bad but it wasn't as this machine was earning serious money inbetween very minor breakdowns but now getting obsolete.

So I took a look at this rectifier block and all it consisted of was a heat sink with 4 stud rectifiers on it to form a bridge. So the over engineering part of me thinks it's probably running right on the limit for 1/4" stud rectifiers.

Sooo, consult the RS book and find some very reasonabbly price stud rectifiers with 1/2" x 20 studs rated at 1200 amps each. Loverly, ordered two pairs andd made a new heat sink out of a big lump of 1/2" alloy plate.

Fit said rectifiers, check with a multimeter for operation and fit. Quick test run and fit the side panels later.

So welding away great and all of a sudden there is this blinding flash equal to two Hiroshma's, one Nagasaki and a terrible pain in my left leg. The rectifiers had exploded and the bits of one had stuck in my leg !!

So much for over engineering and that got consigned to the scrap heap to be replaced by an expensive British made unit waht was a bigger hear of crap from da one, but that's another story.

John S.

Hi David, I'm not trying to run your opinion down, but you don't say if this welder is an industrial one, or one that is aimed at the DIY market. If it is a DIY type, you may find it's duty cycle is non continuous, which is common with DIY type welders, especially at the top end of the power settings. This is not a design fault or shortcut, but a means to make such things afordable to the DIY market.

The duty cycle is something anyone should consider before buying a welder of any short, in that it needs to be within the range you expect to use it.

Apologies if this is not the case.

Regards Nick.