Certainly this is a basic question, but the search function returned no results for arc wander.
First of all, the constants throughout this post are that a Miller Dynasty 200 DX is used, and so is a 3/32" 2% Thorium electrode.
The problem is that when trying to run an autogenous stringer bead weld on 1/8" thick 1020 steel, the arc will not stay centered on the end of the electrode. It strays to one side or the other of the electrode. The arc also will not stay perpendicular to the work surface, but rather it settles in at about a 45 degree angle as though some invisible wind were blowing it. It definitely doesn't look right. On the plus side, once it strays, it stays where it is, and the weld can be continued with decent results.
Things I have tried to remedy this are:
* Changed the maximum amperage settings from 125 to 175 amps DC electrode negative while using a foot pedal for final adjustment
* Changed the argon flowrate in 5 cfh increments from 15 to 30 cfh
* Changed the stickout from almost not being able to see the electrode to extending to a length almost equal to the full inside diameter width of the gas nozzle
* Changed the torch angles from 90 degrees at startup to almost 60 degrees at startup
* Changed torch running angles from 80 degrees to almost 45 degrees
* Cleaned electrode with virgin sandpaper. The electrode appears to be clean and shiny in all places. No pits. No contamination apparent.
* Tightened electrode collet
* Tried both backhand and forehand methods
* Changed arc length
* Slightly ground end of electrode so that the perimeter would not be a sharp 90 degrees. The end is somewhat chamfered now.
* Tried chamfering the electrode using both a straight grind and a radial grind
* Changed gas nozzle from a 6 to a 7
* Put in another brand new 3/32" 2% Thorium electrode, collet, etc.
* Relocated the ground clamp
* Moved the work to another place on the table
After trying all the above, subtle differences were noted, and it was a good learning experience. However, the problem was still there!
Since the excercise was really designed to get to know the machine, I then used the exact same electrode, nozzle, and 20 cfh argon flowrate to run an AC stringer weld on a 1/8" piece of 6000 series aluminum. No matter what experimental adjustments were made on the machine, the arc remained perfectly centered on the electrode. The welds were immaculate as well. Isn't this a twist (at least from a MIG point of view)? The aluminum is actually going better than the mild steel!
Any ideas?
Thank you. Greg
Hi Greg,
You might try grinding a sharp point on the tungsten. The square end or balled end is good for Al, but not for carbon steel.
Check out http://www.pro-fusiononline.com/tungsten/geometry.htm
Hope this helps,
Dale Simonds
Hi Dale,
Thanks for the reply and reference article. I'll give it a try.
Greg
The Dynasty 200DX will not weld with a blunt tungsten must be sharp25 to 30 degree angle. This is an inverter and it will overwork the electronics if you do very much of it. I also don't recomend thoriated- I use 2% ceriated or 2%lanthanated. Thoriated will work but it isn't healthy for you. I've used these machines for a year and if I can help email me at pjseaman@sigecom.net.
Peace,
Could be deflection from magnetic fields. Then when you change to ac for aluminum the magnetic effect is canceled out.
Bill
Greg, pjseaman is right, you should be grinding your electrode to a point. As a rule of thumb a taper of approx 2 to 2.5 times the thickness of your electrode. eg: if your electrode is 1/16" then grind a taper approx 1/8" long or slightly over. I think you'll find this will solve your problem of a wandering arc.
Regards Andrew from downunder
I'll bet it is, like already said, the tungsten needs sharpened. But be sure to sharpen it right, so that the grinding marks are 'lengthwise' with the tungsten. Also make sure the torch hoses are not twisted or crossed around each other. This can cause some arc problems. Also try moving to an area away from your bench and grounding directly to the work to see if the arc centers itself. I have heard of someone having a magnetic bench top because , If I remember right, current was going through it from an nearby outlet leak some way causing it to become magnetized. I believe the person grounded the bench and it fixed his problems. I wish I knew more about this story.
CPB
Thank you all for the input! Turns out that simply grinding a taper at the end of the electrode solved the problem for the DC operation. The cables are laid out a little bit more orderly now too. Glad it was something simple. Would you suggest grinding the electrode for aluminum and AC operation as well? It seems to work fine with a flat electrode. Greg
The miller inverter machines are designed to run with only a ground tungsten AC or DC and it should never have pure tungsten used on it. Only use ceriated, lanthanated or thoriated, and there are some specialty tungstens that are tri-mixed that work very well but these are fairly expensive and I think the ceriated works very well so that is what I use. 2%Ceriated in 3/32" and 1/16" is all I stock and it works for everything, SS,mild steel and aluminum.
Peace,
pjs
See http://www.ckworldwide.com/tech-4.pdf#search='shapes%20of%20Tungsten%20Electrodes'
for Tungsten preparation.
Gong
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