Inverter arc weird arc direction.

[Dr pepper]

I've a messer 140 little inverter machine for general maintenance and the odd fab job.
The machine has worked well untill the last couple of days, the arc seems to travel away from me as though its being blown by compressed air, and the result is a tricky weld ok on one side, but tall on t'other.

Why?

 

[shenion]

Sounds like arc blow. Weld one side and the metal gets magnetized.

It is a black art. I'm and EE and could not tell you without complex calcs and models of a piece of work what would happen in any case other than a flat bar.

In general, try moving the return lead around. Keep it close to the weld or alternate it on opposite ends (or try the center.) Switching the lead polarity can help sometimes.

Sometimes it can still be difficult. In some cases, the return or work lead can be wrapped around the work to neutralize the field. Saw on of the "Biggest Fixes" episodes where they wrapped about 10 turns of the work lead around a 5' pipe to neutralize a natural occurring magnetization.

Using AC will get rid of the problems, probably one of the few advantages of buzz boxes.

 

[Dr pepper]

I'm an EE too, not quite my field though.
I just noticed the leads to my rig are coiled up and shoved under the carry handle from the last job, I'll try again with all the lead straightened out, I spose a slight inductance is significant at the switching speed the rig uses.
I was only welding two bits of 2" angle, never seen this before, must be a reasonable field to drag the ionized zone, the arc looked just like the tip of a gas welding torch.

 

[Drains]

You can get arc blow (or what passes for it) with damp or under-dried rods, especially 70xx, and badly manufactured rods where the metal isn't central to the flux.

And on inverters with an easy-to-turn current control, an accidental knock can turn the current down, for a rubbish weld. Very annoying.

 

[oilcooled :)]

whats an ee

 

[Drains]

whats an ee

Something we used to take at clubs in the 90's, iirc (or more likely, i've forgotten)

 

[oilcooled :)]

ah no seriously is it electronic engineer or something ?

 

[shenion]

Yes, Electrical Engineer.

 

[oilcooled :)]

i should have copped on to that sooner, im studying mechanic engineer.not trying to change topic but can mechanical engineers be fabricating bits nd bobs or is the end job all p*** hard maths

 

[decepticon]

Have heard a few times before that when plates magnatise its effects can be lessened if you hammer the plate a few times. this works better if plates are hot but may be worth a try anyway
cheers

 

[Dr pepper]

My earth wire was coiled up 20 times or so, I was doing some tacks before and it seemed ok, so maybe it was that.
I'd no idea that damp could cause this, the rods I keep at home stick like mad for the first couple of arc ups due to the damp in the 'shop, but this was the first time I had the arc wander about on me, might experiment with that again, maybe not I'd probably blow the trannies in the set.