Been having some problems with our axcess 450 and im finally fresh out of ideas, need some new minds to look at the issue. Problem is only when running SS wire in RMD and accu-pulse programs. With a fresh contact tip it will weld perfectly; stable arc, low spatter, good bead shape ect. Usually after about 2ft of weld, it starts to arc inside the contact tip. Sometimes it runs great for a hour or so, sometimes a tip wont work at all. You can feel the gun bucking and see the wire spring out of the tip as you are welding. I can pull the wire out and see the arc marks on it so I know thats the problem. It only does this with SS, I can weld steel .035 with the same gun and tips with zero issues. I also checked the wire, its dead on at .035 Heres the details.
Axcess 450 w/axcess feeder. Avesta 316L wire .035. Tweco gun with brand new proper size tweco tips. Running RMD with tri-mix on the HE-90 program (told by miller engineer it wouldnt be a problem) 150-240 WFS, 48-55 arc control 36-40 arc adjust. Accu-pulse w/tri-mix on tri-mix program, same settings. 15' torch with new liner, volt-sense lead is uncoiled and attatched (though I have never seen it make a difference on or off) Ground and all connections are solid. Welding on 16ga tube and sheet.
My only other play left is to get a new gun altogether and see if that helps, but I wanted to make sure there isnt something I am missing before I have the boss go shell out the change for that. Like I mentioned it does function sometimes and when it does it leaves some beautiful beads. I need to get this machine working so we can switch our welding from TIG to MIG and save some serious time+money.
Try different brands of tweco style contact tips.
Inverters are a bit more sensitive in this regard.... Not all contacts are the same quality... Look for American made.
How often do you change the linners in the lead. Sometimes this will help.
M.G.
Brand new liner was just put in the gun to try and alleviate the problem to no avail. Tips are genuine tweco parts, I dont think we can get much better than that...
Just a wild guess on My part, but copper coated steel wire has a more [electricly] conductive surface than stainless steel. Might be the problem.
For My spool gun, there are slightly curved contact tips, presumably to get more reliable contact. Is there such a thing for a regular MIG gun?
Hello
Just a WAG on my part. If you changed the liner and tip and it works fine on other types of wires.
Then maybe try a new fresh roll of 316 and see what happens. or even a different brand
Tom
Drawing lubricant on the wire maybe?
The other thing that comes to mind is that stainless steel develops a passive oxide film which protects it from corrosion. Perhaps the oxide film does not work well with RMD?
Does it work with other brands of SS wire?
G'day hoo we dont have a miller rmd unit but I do run a couple of the fronius pulse migs and always seem to have trouble with that size wire. I have found .045 to be much more user friendly.
Switching to .045 isnt really an option, the vast majority of use for this machine will be on 16ga material and I think .045 is going to carry too much heat.
I did run a spool of esab wire in it and had the same issues. I think im going to petition for a q-gun with centerfire tips this week, we have also had problems with porosity when running pulse on .035 steel with at 300-400WFS. Hopefully the improved flow of the centerfire nozzle will fix that.
Fixed most of the problem by adding a wire lube and changing to a heavy duty style tweco tip. RMD works great, and pulse no longer makes the wire arc inside the tip.
However when running pulse the wire does not form a good spray cone, it simply forms a big ball and shoots off. Like an over exaggerated form of globular transfer. Any ideas?
There is an arc sensing lead that is to connect to the work, like a small ground clamp, but needs to be separate from the ground clamp.
The closer this lead clamps to the weld, the smoother your arc will be.
Some of our welders were either not connecting this lead or just connecting it to the ground clamp, or clamping the bare end of the wire to the work with the ground clamp. This makes the lead act like a ground and messes with the arc characteristics.
Could this be an issue?
Tim
No, I uncoiled and connected the volt sense lead to the work as this was my first suspect but it didn't seem to make a difference. In fact I have never noticed a difference with the volt sense lead being on or off in any program, CS or SS. Should that be taken as a sign that something isn't working right in the first place?
I have the end of the volt sense wire installed in an alligator clip, is that acceptable?
An alligator clip is fine.
When our lead was not connected correctly, the machine would weld fine, but occasionally the arc would sputter, and not run as smooth as it does with the lead connected properly.
I guess you've already ruled out wire feed / liner issues?
Tim
Sounds like Your peak voltage is too low. I have NO IDEA how to change the settings to improve it.
By welder5354 
Date 07-25-2010 03:30
Edited 07-25-2010 03:37
Hello, had the same problems with the STT processs on the lincoln power source.
I scrapped the .035 wire and got some .045 wire and i never and a problem since.
I believe somebody on this site told me about this last year.
Try it and make sure you have the correct rollers, contact tip to match the .045 wire.
Hope this helps you, as it helped my problem..
PS: I have been running the first pass on SS pipe (.045 wire) with no purge and the bead is excellent on the inside.
dh
Well long story short we never did get the problems worked out even when I put a new q-gun on it with centerfire tips. Still use the machine, but only for steel now. So we got a MM350P to dedicate for stainless. Runs much better and has increased production greatly.
Only thing that could improve is the color of the weld, now running pulsed spray on 16ga is very hard to keep from getting gray. We had been running a He90/7.5/2.5 blend which yielded a stable arc and minimal splatter but left us with a dark blue/gray weld at best. Acceptable for what we are doing, but not preferred. Tried a Ar66.1/33/.9 mix today in hopes of getting better color. It did in fact give us a nice rainbow band around the weld at the same WFS, however because of the decrease in He content I needed to increase from 150 - 240 IPM in order to get a fluid puddle. Running such a high wire speed on thin material negated the benefits of the Ar 66 mix so I switched back to the He90.
My question is this; is the problem simply that the Ar66 mix is not meant to be ran on thin materials or should I have been able to adjust my arc length and sharp arc settings to get a good weld at 150-180 IPM?
