This mig welding video shows how, why, and when to change the polarity.
One question I get asked all the time is "why does my flux core wire welder not weld worth a crap?" sometimes its a 115v mig welder that is plugged into a 15 amp circuit and on a 25 foot drop cord. Thats easy to answer.
But when flux core questions are asked, more often than not, the problem is polarity. Apparently, not many mig welders out there are aware that the polarity needs to be changed for some flux core wires. With bare wire mig, polarity stays the same. But with flux core, and especially the self shielding kind, Polarity needs to be whatever the manufacturer says. trying to weld on the wrong polarity is a sure fire recipe for Fido's Ass... A hogs butt sown up with a grapevine... A gorilla weld... Stop me please...
Changing polarity is easy. And it makes a difference like night and day.
Lincoln NR 211 and Hobart fabshield 21b both are self shielded wires and both use DCEN. Some of the dual shielded flux core wires use DCEP.
So here is the tip of the day...
Check the manufacturers sheet to know what polarity to use. You can bet the manufacturers want you to buy more wire so they have some skin in the game when it comes to making sure your polarity is right.