Mig Handpiece Problem

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Gents

I have a small CIG Transmig 135 Gas/Gasless which is around ten years old now.

Until recently, I've had no problems with the unit, but of late it seems I have to squeeze the trigger on the handpiece harder and harder to get the zappy bits to flow. The gas pours out quite nicely, just no juice.

I investigated the tap/switch mechanism in the handpiece and found a nice little copper disk on top of the gas valve actuator that makes contact with two little copper studs on a piece of insulating material. This forms the switch.

The disk and studs looked a little oxidised/burned, so a few touches of fine emery, a quick re-assemble and voila! it works again.

My question is - why are the contacts oxidising? Surely the switch is not carrying the full arc current (it couldn't be), so if it is only a switching current why would the oxidisation/burning occur?

Your thoughts would be appreciated.

Regards
Scott

[Grahame Collins]

Hi Scott

Its ten years old and playing up a bit.
I think you have had a good run. In all honesty those original handpiece units are hardly industrial quality. If it persists you can in all likelyhood pizz it off and replace with some generic handpiece like a Profax which could run to around $100.These are much better, substantially built units.

You are correct switching current is 32 volts (by law) so as if you drop a heavy plate on it and it cuts cut there is no lethal current.

Possibly your location (sea breeze? salt) may offer a clue to your corrosion problems.Do you bag up your wire spool when not in use.That would be one of the first things to corrode. Other than that not much to offer you
Grahame

[neksmerj]

Hi Scott,

If you don't follow "Le Experte", Grahame's advice, and you wish to retain your original hand piece, get the contact bits and pieces, gold plated.

Shouldn't cost more than $30 from experience. Just a thought.

PS. Grahame, how are the gumboots holding up?

Ken

[Grahame Collins]

Hi Ken
Well ,I will put it this way.
if theres any more rain more next project will sport a periscope.

Insurance is the word boys ,don't ever let it lapse.
The assesor has been an we are entitled to more than we anticipated.

Because the water was flash flood and contained sewerage things household items like fridges and washing machine are being replaced with argument. Wall cladding in flooded "living" areas will be changed out to 1200 high.In our case the whole wall of the walls as they are fibro (yes asbestos)

As it turns out theres a silver lining in every cloud so to speak.Her indoors hated the current washing machine cos it was too small in capacity.It is cheaper to replace our $1800 Asko with a top line Westinghouse.

Same with the bathroom which had a spa bath which she also hates.The always wanted a shower recess as it is easier to clean The assessor indicated that if the value was equal or less than building said shower recess-no problem -yahoo-- one happy lady.

Grahame

Grahame

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I suspected it may be a case of having had a good run with a cheapo piece-o-crap handpiece. I wish it had the Euro socket so I could simply change it over, but alas, it will be a rewire job.

Yes I am near the ocean, so it is a likely cause. I bag the spool in a garbage bag with a sachet of silica gel if I can find one lying around, and that seems to works OK for me.

When I was in Trade Tools on the weekend, I was looking at the 200 Amps inverter stick welders branded as Renegade. Now, I won't let the fact that I have never stick welded very well get in the way of a good story, but these little units are $288.00, which seems good value to me. I'm itching to try one. My thinking is that if the MIG is cactus, then one of these may just fit the bill - no consumables other than rods, I can weld in the wind, no gas bottle rental just sitting around waiting to be used.....

Does the fact that these inverter units have fine controls, and can quite happily burn up the thinnest of rods mean that they can do the job of a Mig for the home handyman/weekend warrior?

Regards
Scott

[Grahame Collins]

Hang on there Scotty
WHOA back mate!

Don't scrub the mig yet on the basis of a dodgy handpiece.
Maybe you can get away with a spare parts switch from another brand mig handle.

I am sure there must be a clever repairer around Brisbane somewhere.Dick Smith or one of the oppo electronic supply places should be able to supply something close.

Thin in your case will mean 1.6m rods but what do you Expect to weld. 1.6 th maybe 2 mm may be the thinnest.

As always, I refer you back to the mantra for buying cheepee chinese electronics welders which is warranty ,spare parts and available repair agents.
It maybe the bees knees but without the above she aint worth zip.

regards
Grahame

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Grahame

Thanks for the dose of reality mate, you are quite right of course, but you know what it's like - the shiny new flash model just HAS to better than the old faithful boring plodder.

I suppose the guy at the welding shop put the fear of God into me with his rough guesstimate of $150 for a new torch + fitting. I could probably bodgy-up a momentary contact switch from Dick Smith or suchlike as suggested, and I should at least give that a go first.

I agree wholeheartedly with your cheepee Chinese mantra, I should know better by now, but they just look so interesting! I said the same about most of the Chinese power tools I've bought over the past 5 years that now sit at the bottom of a landfill with new houses built over the top of them.

Anyway, she seems to be working well now after the touch-up with the emery, so maybe I'll have to think about it again in five or ten years.

I'll give her a good run on the weekend putting a new floor in the old box trailer. She always did love to run flat-out on a long welding run!

Regards
Scott