Help newbie tig? electrode keeps melting

By Lawrence (*****)

Date 05-17-2005 18:18

Hey Doc,

Two quick helps that will change everything.

Make the electrode negative (DCEN) (DC Straight Polarity)

As possible change to a 3/32 Thorium, Cerium or Lanthanum electrode. The pure tungsten will never keep its point very well even with the correct polarity selection.

By THE DOCTOR Date 05-17-2005 18:29

The st 300 is a somewhat limited unit it doesn't have an actual switch to change polarity from ac to dc i believe it is an AC high frequency unit as i don't have to scratch arc start so i think i could change polarity by switching from positive the way i currently have the torch on to the negative which i currently have the ground on? will that work?

By Lawrence (*****)

Date 05-17-2005 23:02

Thats exactly right Doc!

Change polarity by changing the work clamp and torch to opposit lugs.

By ssbn727 (*****)

Date 05-20-2005 04:35

HEEEEEEE!!! Hee!!! HEEE!! HEE!!!! I'm sorry but, I just could'nt help it!!!

Man - O - Man!!! is that tooo funny!!!!

Hey DOCTOR! The Pow Con 300 St is a DC only inverter type power source primarily designed to perform SMAW and GTAW and you could hook up a voltage sensing wirefeeder to do some GMAW or FCAW with questionable results, but, that's another story...

Anywho, Many moons ago when these puppies first came out into the market, they were definitely ahead of their time and as with anything new, they had their fair share of problems... One of them were just putting up with their ungodly noisemaking ability from the High Frequency step up transformers inside which by the way have nothing to do with starting the arc for you on this machine, but that is another story too!!!

What you have is capacitive discharge!!! This is what starts your arc transfer and as Lawrence so eloquently put it, YOU NEED TO REVERSE THE WORK CLAMP and TORCH connection to the OPPOSITE LUGS on the machine...

Nonetheless, Whatever you do , DO NOT OPEN THE MACHINE IF YOU DON'T KNOW ANYTHING ABOUT THE INSIDES OF THIS MACHINE BECAUSE, THIS IS NO LAUGHING MATTER!!! YOU CAN EASILY GET ELECTROCUTED IF YOU DO'NT KNOW YOUR WAY AROUND!!!!!

Cyclomatics out of California used to make this power source but, then they changed so many hands as to who has updated info on that machine that I'm afraid I could only suggest bringing it to someone that is familiar with that line of power sources, in other words, a qualified independant welding equipment repair shop in case you needed any service to be performed on it.
Electrode or in your case GTAW(TIG) Torch Positive equals tungsten balling up or reverse polarity... For TIG, stick to Electrode or TIG Torch on Negative which btw, equals straight polarity and that's where you want to be!!!

BTW, does your call sign represent that you're some sort of Doctor?
I hope you do not mean a doctor of welding, do you? I ask this because I would not be convinced of that, to say the very least based on your query!!!

Respectfully,
SSBN727
Run Silent... Run Deep!!!

By THE DOCTOR Date 05-20-2005 13:51

In the first place thanks Lawrence for squaring me away! It works just like it's supposed to now. Next would it be possible to weld aluminum with this unit? From what i have read i need an AC tig welder to weld aluminum and The ST 300 takes AC and converts it to DC. In talking to people at welding supply houses they say it can be done but the results will not be pretty. Thanks again for your time

DOC out

P.S. I am a Dr. of Chiropractic not welding, and i have had my machine apart 2 times once to change the power input from 3 phase to single phase and second to replace the fan which much to my dismay also acts as some sort of transformer which from Arc Products cost me $166.

I did manage to do all this without electrocuting myself.

By Lawrence (*****)

Date 05-20-2005 14:18

Doc,

Your Whistling PowCon has limited ability to join aluminum.

With 100% helium gas and both abrasive and chemical surface prep (abrasive really isnt enough to remove the oxides) Aluminum is commonly joined. However, DCEN is generally applied to heavier sections (over 1/4 in) and can take some practice.

By THE DOCTOR Date 05-20-2005 14:37

By 100% helium you mean no argon at all? I have read that using helium along with argon helps to aid in penetration with aluminum. What does the helium do on its by itself? What sort of chemicals should i use to clean the aluminum? Do i use a similar flow rate as well 15-25 cfm?
The AC has a cleaning action from what i have read and is that why it is preferred?

I am reading the welding bible and welding fundamentals and another one i can't remember right now. Are there any books you would recommend or some pages on this site that might be archived related to tig that would help someone with my limited knowledge and skill?

Thanks again for your time and patiencs

DOC

By jwright650 (*****)

Date 05-20-2005 15:13

Hi Doc,
Yeah there should be a lot of info in the archives on GTAW of aluminum.
-most of it posted by Lawerance :)
Have fun with your research, max out the days to 999 and number of posts to 100 for best results.
John Wright

By CallMeTigger Date 06-08-2005 04:57

Helium is really dense, kick up the flow a bit. Helium makes the arc hotter.

Clean with stainless steel wire brush or some special aluminum solvents. Good old wire brush does it for me.

By Lawrence (*****)

Date 06-08-2005 14:55

Dense?

I suppose thats a relative term. But Helium is the second element on the periodic table, meaning of all the elements currently known to man it is the second lightest, about 1/4 of the density of argon.

Increased flow (which is the correct thing to do with He) is related to its greater dispersal properties which are tied into it's "relative" density :)

By ssbn727 (*****)

Date 05-21-2005 00:16

Hey Doctor!

I've got this kink in my lower back - just kidding!!!

Anywho, The reason for the warning is that your machine has a capacitor bank that must be discharged in order to safely work on it's internal components... However, since you already mentioned that you've done some limited work inside already, I wo'nt bother to inform you about the dangers of working inside without knowing what your getting into!!! SHEESH - what a sour puss!!!