MIG vs Flux Core--Why polarity change?

Got my Hobart 125 in and my regulator/gas kit, but bottle is late in shipping.

So I set everything up and when you add the gas kit, they tell you to swap a couple of wires and reverse the polarity of the welder.

Why is this? What difference does it make?

 

I wondered the same thing when I did mine. Would be intresting to know.
As for the bottle. I went to Air Gas and bought a tank for like $80 and it costs like $35 to fill it. That was a smaller one. Stands about 3ft tall. I now have it and a large one, I don't recall the sizes. Any smaller than the smaller one I have and you may find yourself having to fill it often. Just a thought.
Do you have a welder cart?

 

When I replaced the floor pans in my Falcon I rented a flux core mig. I changed the polarity and it lowered the heat and it stopped blowing holes.

 

All it is is the characteristics of the flow of electrons, MIG uses dc+ polarity, as for gasless/fuxcore uses dc- polarity.

 

I am trying to figure out why...does it have something to do with how the electrons react to the gassy environment?

Seems like it should melt steel either way...

My tank is about 3' tall, 40 cf. I wanted one that was small enough to be portable. This one weighs about 30 lbs empty.

 

on a mig/flux machine the option for polarity adjustment has to do with the characteristics of the wire itself; Mig wire = solid wire, fluxcore= innershield (shielding flux). Now if we're talking about stick welding, DC is almost always prefered over ac these days, much nicer welds, easier to work with, Use DC with tig too. For the longest time, Ac was all there was in the old buzz boxes.. my first tank was a 40cf as well. I love it when i take my smaller welder out on the job, But be careful it runs out quick, there goes another 60 bucks! I have a larger 139 as well and that sum'bitch costs 100 bucks to fill! but if you think about it It's worth it. I use that bottle on my 220 lincoln mig.

 

How long is the 40 CF going to last me?

Luckily, I live in the middle of a bunch of refineries and can get my bottles filled cheaply, and quickly. There are at least 5 places within 30 minutes of me that fill the welding bottles and sell welding supplies.

I was quoted $13 to fill a big tank with 75/25 argon, which I thought sounded VERY reasonable.

 

The way I weld 40 cf will last about 2 weekends worth of welding.

$13 is hella good. It costs me $25 for a 20 cf cylinder exchange.

I'll have to look up the physics behind the polarity change and get back to you with an explanation.

 

From the Welding Manual:
"A phenomenon in electrical welding where the magnetic forces in the work can cause a wind-like force that blows shielding gasses away. Usually happens in corner welding and can be avoided by switching polarity or moving the ground clamp."

Reverse Polarity - In electric welding, the term refers to a DC setup where the work is made negative, and is called DCRP. It is the opposite of DCSP, or straight polarity. ​

 

Lucky!...it used to cost me $20 to fill up my 40cf. Then it went up to $25, and when i sold my welder it was up to $40

 

Make sure you use 75/25 mix.

 

Shortly after I bought my welder, I was replacing the spool and noticed the polarity was still set for flux core. It had already been loaded with solid core and had a partial bottle of gas, but they did not switch the polarity. I switched it per the diagram, but I did not notice any difference. But then, I was just learning to weld, so the welds didn't look all that great anyway.

 

The polarity change is to compensate for the depth of weld. Changing the polarity makes the arc jump from the opposite side and reduces the risk of burn through.

If your stock is positive polarity and the wire is negative then the arc originates with the wire and jumps to the work. If you change the polarity to the work being negative then the arc starts at the work and jumps to the wire.
The heat at the work piece gets hotter faster depending on the polarity.

 

I thought the polarity change was due to,,,, Global Warming,,,,Gore y huh???

 

sorry to contredict you guys but depending on the type of fluxcore you use and if you use CO2 as gaz you are not suposed to change polarity on fluxcore wire .

flux core is meth to be use on thick material where penetration is the formost important factor to the weld that is exactly why it blows holes in body panels and such straight polarity is use on all type os semi automatic process (flux, or wire) and that to prevent projection

the onley execption is auto proctected wire (wish is bull****)

use tig on thin parts it work way bether or if you have onley a mig use wire get the volt down and wire speed too it should sound like a bee swarm not a big tiking sound (hard to describe i should records the sopund one day)

use flux core if you need to do 1/8 thick and more, and ajusted in a way that it sound like water out of the focet or sand on metal and use STREIGHT POLARITY it will save you a hell of a spaters cleanup.