Best motion to use when Mig welding?

[zx666r]

I use a slow back and forth motion. Is there any other way of doing it better? My welds are coming out fine, but I'm curious if there's a better way to do it.

[crashinaz]

Too many variables. Fillet, butt, overlap... Material... Thickness... The machine... Single pass, multiple pass, etc. Go onto millerwelds.com... There are some how-to's and videos. Playing around on scrap and doing a little destructive testing in the vice with a BFH can teach you a lot actually . If you want to post some macros of your beads, I'd be glad to put my 2 cents in though.

[99345hp]

In the tech college I went to we were taught to do circles with a slight drag angle. That will work in flat, horizontal and overhead groove and fillets with single or multiple passes. If we went verticle we did a weave, which is a wide side to side, like building a bridge. All of our welds were destructive tested, so I know that motion works. Oh yeah, BTW I HATE MIG. Dont take this the wrong way and this is just my opinion. I think Mig welding is the most chicken shit welding there is. I can do it, and am trained to do it, but I wont trust anything welded with a mig but sheet metal. Just my $.10.

[79Jeep]

i generaly use the half moon technicque. seems to work pretty good on most applications, but it really depends especially on thickness of the material

[430 hp 70]

99345hp -

do you care to explain? i dont see how the weld is any stronger with a tig. i could see an arguement that maybe the mig weakens the metal through the welding process, but i guess i just dont understand how a mig weld is weaker? is it the penetration? the filler? the process? btw, im only talking about mild steel, the other metals are a given.

ive tested a lot of my own welds, and i find that i get some sort of failure of the metal somewhere else. whether a bend, stretch or tear, it never happens at the weld.

[MikeGyver]

Originally Posted by 430 hp 70

99345hp -

do you care to explain?

I'll explain for him, and he can correct me. Stick welding and TIG welding allow you to adjust the heat concentration on the go by adjusting the arc length, and the pedal with TIG. If you try moving the MIG gun closer or further from the weld, it will just screw things up. You have to do all the adjustments on the MIG with the knobs, before you weld.
A good weldor can run a perfect bead the first time using stick or TIG, but you most likely have to do a test weld or two with MIG.
The major benefit of MIG is that once it is correctly adjusted, any monkey can make the same weld repeatedly all day long.
And correctly adjusted, MIG is good for any thickness of metal within the machine's capability.
I have both, and if I have one small weld to make that either process will do, I prefer TIG.

[430 hp 70]

i understand the ease of use for the pro, but im more interested in whether a tig can produce a stronger weld. tig welding is no doubt in my future, especially with the ability to do stainless and aluminum, but i dont see why a mig is bad in any sense for mild steel. in fact, i believe too many "pros" actually make a tig weld weaker, especially since many are going for the look.

btw, the one way to make a mig weld look bitchin on any thickness steel is to do the series of tacks. if you get good, you can mimic a tig. its not a strong weld by any means, but it looks cool for the non structural pieces.

for me, its all about the weave. the guys on the miller site are pretty unanimous in believing that the circles will form a slightly weaker weld. it has to do with moving forward, allowing the metal to cool, and then circling back and reheating it. i dont really see how since its only a fraction of a second, but i dont do this for a living either.

tim

[99345hp]

While mig welding, if you dont use the correct motion you wont have proper penetration. You can turn the heat and wirespeed up, bit then you are dealing with other problems when you do that. A mig weld is also more brittle than a tig or stick weld. This will lead to more fatigue cracking. Why do you think they never use mig as a process to weld piping?
As far as making it look like a tig weld. If you use a circle motion you can make it look like a tig weld. You want to pull the trigger and circle to in front of the puddle, then back around to just to the rear of the puddle. Just make sure when you go forward you get out in front of the puddle to ensure you get good penetration into the base metal.

If you are grinding the face off of your welds a mig will give you a lot more trouble too. Mig welds seem to be very much harder to grind smooth.

[jdustu]

Originally Posted by 99345hp

While mig welding, if you dont use the correct motion you wont have proper penetration. You can turn the heat and wirespeed up, bit then you are dealing with other problems when you do that. A mig weld is also more brittle than a tig or stick weld. This will lead to more fatigue cracking. Why do you think they never use mig as a process to weld piping?
As far as making it look like a tig weld. If you use a circle motion you can make it look like a tig weld. You want to pull the trigger and circle to in front of the puddle, then back around to just to the rear of the puddle. Just make sure when you go forward you get out in front of the puddle to ensure you get good penetration into the base metal.

If you are grinding the face off of your welds a mig will give you a lot more trouble too. Mig welds seem to be very much harder to grind smooth.

What exactly do you do?

Mig is used a lot for pipe welding, but mostly in fab shops. Stick is just way more practical for field work, and tig beats all when it comes to root passes.

I do a lot of medium/heavy duty fab work, and mig is used extensively. I would trust it with my life, or it wouldn't be used. Shoot, the Navy is working on a way to Mig weld titanium! You think they'd be doing that if it was inherently weak? And I'm going to assume you've never even heard of spray transfer?

The old "a monkey" could mig weld is just not true. Why do you see so many cheap production mig welds break? It's not the process, it's the $10-12/hr welder. Besides setting the machine's voltage and wire speed, you've got angle, travel speed, joint type, ect. ect. Every welder should be able to tune his own machine because everyone moves a little different.

With ANY type of welding you need to use the proper angle, motion, ect. Each process has it's benifits and drawbacks, but to say mig is only suitable for sheetmetal is flat out wrong.

-Josh

[mg98ta]

I agree with jdustu. I work in a fab shop making skid steer attachments. We use the back & forth motion and the circular motion. Different welders use different techniques. Both of these motions work great when you are welding rusty or dirty material. Our stuff is tested out in the field and severly punished. Most of any breakage comes from the steel it's self, not at the welds. That's were testing comes into play. All of our products are tested before we put them into production for sale. We may have to use something thicker for strength. Different types of material come into play also. A material that is real hard wiil crack or break before it will bend. It depends on what you are building, repairing, or making. Hope this helps.

[99345hp]

I agree with both of you, mig does work, but I dont like it. I guess I am biased to tig and stick because those are the only processes we use. I have heard of spray transfer, but never tried it. The only type of "mig" that i have seen done on pipe is flux core with a shielding gas.
I think mig is used primarily in fab shops, because it is much easier to train people to run a mig gun. If your welding the same part all day long, there is no need to adjust the machine. Just point and shoot.

[BADD SS]

Originally Posted by jdustu

What exactly do you do?

Mig is used a lot for pipe welding, but mostly in fab shops. Stick is just way more practical for field work, and tig beats all when it comes to root passes.

I do a lot of medium/heavy duty fab work, and mig is used extensively. I would trust it with my life, or it wouldn't be used. Shoot, the Navy is working on a way to Mig weld titanium! You think they'd be doing that if it was inherently weak? And I'm going to assume you've never even heard of spray transfer?

The old "a monkey" could mig weld is just not true. Why do you see so many cheap production mig welds break? It's not the process, it's the $10-12/hr welder. Besides setting the machine's voltage and wire speed, you've got angle, travel speed, joint type, ect. ect. Every welder should be able to tune his own machine because everyone moves a little different.

With ANY type of welding you need to use the proper angle, motion, ect. Each process has it's benifits and drawbacks, but to say mig is only suitable for sheetmetal is flat out wrong.

-Josh

Agreed

All welding is a skill, I have seen many structural stick welds fail because of inept workers....

hell, we fluxcore alot of structural steel now due to speed. In my shop I'll stick with mig for anything that is going to be a series of fairly long welds. If you adjust the machine right, it's a great process. $10-12 dollar laborers are the problem imo.

[99345hp]

yeah the cheap labor running a mig welder all day has really really killed the welding trade. I was an x-ray tig welder for Eaton Aeroquip for a year, and they dont even pay over 15. The only reason they do that, is because other "welders" in the area were topping out at that amount. The only way to make a really good living welding is to go on the road.

[Z48LT-1]

430 hp 70's comments about making a series of tacks seems like an approach for people with poor motor skills, like me. Anyone care to chime in on the pros and cons of this method? Is it a reasonable way for beginners to begin? Is it actually weaker than a continuous bead weld? Why?

FYI, over at the metalmeet forum, here's a thread about welding thin sheet metal where the 'instructor' uses a series of MIG tacks with impressive success:

http://www.metalmeet.com/forum/showt...in+sheet+metal

(Registration probably required, but it's free and there are some genuine wizards there.)

So, if anyone else would like to comment on the series of tacks method, I'd be very interested.

Cheers -- Gary

This isn't a hijack, is it? ;-)

[430 hp 70]

Originally Posted by Z48LT-1

Anyone care to chime in on the pros and cons of this method? Is it a reasonable way for beginners to begin? Is it actually weaker than a continuous bead weld? Why?

its not a good way to learn at all. its only good when you need a GREAT looking weld on something that is not a structural part. learning to do something the wrong way makes it much harder to learn the right way. but learning the right way will still enable you to do it the wrong way easily... get my drift?

a constant weld will yield constant heat and therefore pretty constant penetration. but, tacking concentrates the heat in one area that then dissapates as it spreads outward. so, your going to get great penetration in the middle, but less as it goes outwad. when i do the tacking for looks, i will start my next weld on the outside of the first, and allow it to build until it over laps the center of the first weld. this gives me the most penetration since im not having to pentrate my first weld, but its still not the same as a constant weld.

one other con is the heat cycles its putting the metal through. for strength, ive always found that one heating and an air cool will be the best. ten, twenty or more heating cycles can't be good.

any comments????

[v8pwr]

I feel that those who do not weld professionally should look to a professional for real advice . MIG is a great process when used correctly , it does have drawbacks though as ALL welding processes do . TIG looks awesome and can fuse almost any metal . MIG/MAG is superior in any type of production , shop or field . SMAW is running on it's last leg , affordable but it just can't do what a cored wire can do . If you want looks , go for TIG . If you need speed , go for MIG/MAG . The weldor is actually what makes the weld sound and look good . It's easy to have a bad looking weld that would pass inspection and a good looking weld fail . We're fusing metal for a specific purpose and it's that purpose that specifies the process . A bad point of MIG that hasn't been pointed out is that in using 100% argon will result in a brittle weld due to the rapid heating and cooling of the heat affected zone .

[MikeGyver]

Originally Posted by 430 hp 70

...its not a good way to learn at all...any comments????

You left out contamination. On a normal bead, the start is colder than the weld, and it won't float all of the crap out of the weld/base metal interface. As the weld continues, all of the junk or gasses float out of the metal. At the finish, anything bad in the metal gets frozen there. That's why for the highest quality welds, grinding out the end of the last weld before restarting the bead is sometimes done (also to give a more uniform bead).
So every time you start and stop a weld, there is a chance of getting porosity and/or inclusions.
As far as a series of tack welds on sheet metal, that is a common way to overcome the inability of older or cheaper MIG welders to run a constant bead in sheet metal without burning through. There is nothing wrong with it in such thin metal.
Pulsed MIG has overcome this, a good machine will join sheet metal with one continous bead.

[2002Z28Camaro]

ok as far as the motion on mig i use the half moon 90% of the time but sometimes i make small circles i feel its stronger im no pro so i dont know but they both come out preety good looking

[tylerangle1990]

figure 8s have always been my weapon of choice...comes out really good looking and I've never had issues with strength

[01ssreda4]

i use a Z pattern for most all wire gun welds on the 3/8 carbon i weld at work. also i dont go for the rippled TIG look, i prefer very smooth fluid like motion to produce a slick top to the weld. thats my preference. also, properly done by a skilled welder i believe stick tig and mig can be done to make very strong welds. my choice for precision: tig ......my choice for speed: mig..... my choice for mobility and equipment simplicity: stick.