MIG welding

[Cursitor Doom]

Gentlemen,

I need to replace the liner in my MIG welder. The one that's coming out is the 'bicycle brake cable' type where the welding wire's conduit is essentially identical to the tightly-wound coil type sleeve you find on old bikes: a metal liner and thus conductive. The replacement new one has a PTFE liner. It's much less friction and should feed the wire more smoothly than the old one. However, I'm left wondering how welding current is supposed to get to the wire since it will be now running inside an insulated sleeve. So.... Anyone know?

[Fredxx]

There is usually an outer sleeve that has a cable carrying the current and the welding wire in a sheath.

Cable is connected to power at the welder end and connected to the tip holder the other end, then current passes through the 0.6 or 0.8m tip onto the wire.

For me, most lack of 'smoothness' has been the wire fusing to the tip.

[Muddymike]

Power transfers at the tip. Arking in a worn tip causes jerking in the wire feed.

Mike

[Cursitor Doom]

It just seems to me like a very tenuous connection to rely on. As the wire travels through the copper tip there must be some times where there is no contact at all and even when there is contact with the tip, the 'footprint' as it were of the contact area is truly tiny for such relatively high currents ! I'd have expected a system which relied on that concept to provide only intermittent power to the wire. :-/

[John Rumm]

The tip is quite long and should be a fairly snug fit.

[Cursitor Doom]

Right, so in that case, replacing a metal-sleeved wire conduit with a PTFE lined one requires no additional modification. Well, we'll see tomorrow......

[Muddymike]

So what was the outcome?

Mike