The other day, I picked up an old Miller Econo Twin (AC/DC 150amp TIG with High Frequency). I've only done MIG welding in the past and am having some serious trouble with this. I've got books from the library, read some things on the internet and watched hundreds of hours of Monster Garage and American Chopper, haha...so, I'm not just being a tool and too lazy to look.

Anyway, the problem is that when I finish a weld, the electrode gets red hot and melts back into the cup, making me lose maybe 1/4"-1/2" of it and having to resharpen. I've tried running between 20-30cfh of Argon and let it flow for atleast 10-20 seconds after finishing welding, but it's already too late at that point. I'm using a 2% Thoriated electrode on some Mild steel at 60-95 amps. The last time I stopped welding, the freaking cup cracked and I think the collet got melted to the collet body because it was so hot...

What might I be doing wrong here? Is the electrode contaminated or is this because I don't have a foot control (which I think would only control the high frequency carrier on this model, and doesn't stop and start the voltage)?

I'd appreciate any suggestions before I waste more electrodes

 

hi ion
If you don't have a manual for it here's one double check settings and make sure you have not set up your machine on DC reverse

http://www.millerwelds.com/om/o302j_mil.pdf

 

The only time ive seen an electrode melt off and the cup crack is when the welder is used without shielding gas, but DC positive could also cause this because then all the heat is directed at the tungsten and not the metal workpeice.

 

, a direct-current welding circuit maybe either straight or reverse polarity. When the machine is set on straight polarity, the electrons flow from the electrode to the plate, concentrating most of the heat on the work With reverse polarity, the flow of electrons is from the plate to the electrode, thus causing a greater concentration of heat at the electrode. Because of this intense heat, the electrode tends to melt off; therefore, direct-current reverse polarity (DCRP) requires a larger diameter elec- trode than direct-current straight polarity (DCSP).

 

Awesome, thanks for the manual and the tip! I just got around to switching it and now the electrode doesn't melt, yay! I just ran a couple beads along some scrap metal and it worked much better. I don't know how I forgot that it's not the same configuration as stick welding, oh well.

Thanks so much man, this made my day Now, I just have to remember not to wear white clothing when welding, because I bet my eyes are going to be sore, tomorrow. Damnit.

 

Glad to hear it helped you Ion I have never heard of getting a flash from white
clothing before,you might look into it further and be sure you have at least one piece of real glass in your helmet... plastic does not stop harmfull rays.
Don't get to many flash burns in your eyes you need them for welding

 

I agree with the rest of the posts to check the polarity of the welder. Make sure that for steel that you are running DC negative (-) . Not DC pos (+) or AC. Also make sure that your electrode is a good quality electrode. I've had guys at the shop grind on the marked/painted end and then the electrode basically becomes virtually impossible to distinguish from a mild steel filler rod. When you try to weld with a filler rod it makes a mess. Speaking from experience it sounds dumb, but i've had it happen.

 

You can burn your eyes from wearing light shirts. The light can reflect off of it and up into your hood. Today before I left, I saw a few welders with their faces peeling from this.

As for distinguishing weld wire from tungesten...after they get you on this trick a few times, you can tell the difference pretty easily.

 

Steel/stainless/titanium DC NEG and hi freq set to start

Aluminum AC hi frequency - continous