I'm trying to weld together a roll bar for a buddy and I'm having issues with air pushing out from behind the weld at joints. I am using a MIG 200 amp? 220v welder and the tank is almost full with good line pressure (~23 psi). What gives? How can i keep from having to grind these down and re-weld it.

The welds look exactly like trying to MiG weld without the gas on. And will weld perfectly fine intermitantly. Kinda like a really f'd up stitch weld.

Sometimes when you are welding on something that is sealed at both ends, gas and heat can build up inside and push through while you're welding. I know some cage builders who drill a tiny hole near one end of the tube to let gasses escape so they don't mess up the weld.

some other ideas....
pull the nozzle and make sure that spatter hasn't built up inside
check to make sure the gas isn't leaking out in the machine somewhere
you might look into getting a flow regulator instead of a pressure regulator, I've heard that's what you're supposed to run on MIG
if you're using a prelube swab on the wire before it goes into the contact tube, you may need to pull the wire out and clean the tube. I've had one that got a lot of old oil and dirt built up inside the tube and started welding like I was welding on rusty metal.

you might look into getting a flow regulator instead of a pressure regulator.

very good idea, becouse if you have too high of gas flow, it will actualy pull contaminants into the weld causing pin holes (poroisty).

Thanks for the help.

I've cleaned the tip and made sure the gas holes at the end weren't clogged.

I will have to look into a flow regulator too.

For now I guess I'll just drill holes and grind re-weld if I have to.

You might also check the gun itself. Most of my experience is with the bigger Tweco guns but sometimes the liner interface (where it anchors in the gun) springs a leak and you'll never notice it until you pull the trigger without your gloves on...

I've seen brand new Tweco guns from the factory in which the braided copper wire mesh actually pushed the cover gas hose off of the nozzle inside the gun. If you don't feel a breeze around the trigger, probably not it.

You might also check the gun itself. Most of my experience is with the bigger Tweco guns but sometimes the liner interface (where it anchors in the gun) springs a leak and you'll never notice it until you pull the trigger without your gloves on...

I've seen brand new Tweco guns from the factory in which the braided copper wire mesh actually pushed the cover gas hose off of the nozzle inside the gun. If you don't feel a breeze around the trigger, probably not it.


I'll try that after I eat here. I don't know what gun it is but its a welder my gramps bought in the 70s.

I did drill a cross tube at both ends before I welded it and ended up with the same effect.

I also noticed that it does it after I've been using it for a good 5 min. Not constant welding but weld, reset, weld, reset kinda thing. If I went beyond the duty cycle could that cause it?

The gun was not leaking. I really think it has something to do with run time 'cause if I let it set its fine.

In my frustration over the situation I think I put a little too much heat to a couple spots and am generally dissapointed with the welding on this project. Here's a couple pics with the visable stuff done, now I just have to do frame tie-ins.

http://img325.imageshack.us/img325/6943/tollbar0015qn.jpg

http://img325.imageshack.us/img325/8184/tollbar0027ck.jpg

http://img325.imageshack.us/img325/7664/tollbar0034po.jpg

http://img325.imageshack.us/img325/1354/tollbar0043hb.jpg

I've seen a lot worse. :grinpimp:

If you're exceeding the duty cycle of the welder it may do that, or it there is something wrong with it. As it heats up the impedance increases and will cause your settings to fluctuate. Truth is, I'm not sure what I would expect to happen then...must be getting late.

My gut feeling is that you need a flowmeter on your gas, if you indeed are just running a straight regulator.

I noticed the truck is sitting outside. You're not trying to weld in the wind are you? :flipoff2:...the search continues. Are you going to X that thing up the other way too or leave it with only the one cross brace?

I had the same problem with my milermatic 175 a while back. There's some solenoid (that's what the guys in the shop called it though I doubt it's what I would consider a solenoid) that controls the gas flow (inside the welder) and it was getting clogged up. It seemed like an intermittent problem and would cause porosity. Took it in for warranty service, they cleaned the solenoid out and that was the end of my issues.

I had the same problem with my milermatic 175 a while back. There's some solenoid (that's what the guys in the shop called it though I doubt it's what I would consider a solenoid) that controls the gas flow (inside the welder) and it was getting clogged up. It seemed like an intermittent problem and would cause porosity. Took it in for warranty service, they cleaned the solenoid out and that was the end of my issues.

This guy?
http://img161.imageshack.us/img161/8610/solinoid0027ck.jpg

How the hell does this thing come apart?

This happens to me also intermittently. Be welding along and then sometimes it acts like it's having an allergic reaction to the metal. I run an adjustable regulator too. Humm, that little dude could be the problem.

I realllly need to get a new liner in my mig. where the hose exits the handle it'll kink if theres too much pressure on it. lately i've been having to run the hose over my shoulder to keep this from happening. :(