Mig Welder Caught Fire

[Dave TointonParticipant @davetointon92281]

G’Day All,

I was happily welding away with my chinese mig welder when it stopped working and nasty black smoke billowed out of the case. Fortunately I always have an electrical fire extinguisher close by and a quick squirt put it out. The cause of the problem : where one of the output leads emerge through a steel bulkhead via an insulated brass bolt has overheated and the insulation material has caught fire! The melted remains appears to be some sort of plastic, my question is What sort of material should I use to make a new one ? Needs to be electrically safe and hopefully inflammable. some sort of fibre stuff comes to mind.

Thank you for your advice,

Regards

Dave Tointon

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Dave TointonParticipant @davetointon92281]

[Dave TointonParticipant @davetointon92281]

Perhaps that should be NOT inflammable Sorry.

[Richard ParsonsParticipant @richardparsons61721]

Dave The real answer is ‘Ceramics’. I would have a look around for ceramic insulators. These are the sort of thing which was used on electric stoves. I do not know if you can buy them in the land where the ‘Cross’ hangs in the sky’. I used to buy them in an Aladdin’s Cave of a shop back in the UK. You could buy almost anything you useful could imagine there from a bicycle tyre valve to a replacement ether tube for your gas hob.

[Gordon WParticipant @gordonw]

If you are referring to the bushes which lead the LT thru’ from the transformer you can probably buy spares, I made my new ones from a bit of nylon rod. You might find plastic drain rods are the ideal size. BTW the problems on my old welder were caused by a loose hairy strand on the lead up to the torch, now fixed, and with a new liner, good as new.

[John McNamaraParticipant @johnmcnamara74883]

Hi Dave

 

If you happen to be near Melbourne I have some 20mm electrical fibre board. I will be happy to give you a piece to turn up on the lathe to remake your feed through.

 

PM me.

 

Cheers

John

[John Wood1Participant @johnwood1]

If it’s just a bush then I understand one can get machinable ceramic from (I believe) RS Components. I have made many insulation components in the past from Tufnol which is a woven fibre material rather like paxolin but not brittle and easy to machine.

 

Hope this helps – John

[_Paul_Participant @_paul_]

Is it the type that has a feed to the brass part from the welders internal windings then some kind of external “lug” nut to hold on the cable connector? if so it sounds like “Bakelite” (or it’s far eastern equivalent) with a brass connector cast in to it?

 

I would guess it has come loose internally through thermal expansion-contraction over a period of time eventually reaching the point where the resistance has caused enough heat for it to fry.

 

As to replacing it why not do away with it and wire straight back to the internal rectifier simply putting a grommet in the hole where it was to protect the cable.

 

Regards

 

Paul

[Neil GreenawayParticipant @neilgreenaway71611]

Hi There,

 

I would either make it from tufnol sheet with a brass conductor passing through, or you could maybe get some paxolin board from an electrical wholesaler.

 

Alternatively a welding supplies supplier may have insulated bulkhead connectors that could pass through a welder panel. Another alternative is to fit your welder with two dinze sockets on the front panel that can accept dinze plugs on your welder leads – see an example at http://www.ebay.co.uk/itm/panel-socket-connector-10-25mm2-100-200A-1-PCS-/110553434766?pt=LH_DefaultDomain_3&hash=item19bd7f8a8e.

 

Hope this helps,

 

Neil

[Neil GreenawayParticipant @neilgreenaway71611]

Here is a UK supplier – bigger connectors but lower price and supplier in UK.

 

http://www.ebay.co.uk/itm/Welding-Panel-Socket-Dinze-Type-35-50mm-Female-/160505308281?pt=LH_DefaultDomain_3&hash=item255edca479.

[Dave TointonParticipant @davetointon92281]

Thank You Gentlemen, many good solutions there. I found a bit of nylon kicking around so will turn something up out of that but will keep an eye out for something ceramic. Thank you for the offer John but I am in Queensland, Beautiful one day, perfect the next.

Regards

Dave Tointon

 

[frank brownParticipant @frankbrown22225]

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

[Dave TointonParticipant @davetointon92281]

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

[ChrisHParticipant @chrish]

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

[John Stevenson 1Participant @johnstevenson1]

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.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Dave Tointon on 04/03/2012 10:12:50:

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

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.

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