MMA vs GMAW

[super noob]

The only time I prefer a mig is when lying under a vehicle....a small torch makes life so much easier than wielding a 14" stick rod! Or on super thin .020" bodywork...but then again I've got a tig for that

I'm sticking to imperial it makes sense in my brain....my lecturers hate it too!

One of the old school lecturers who used to be a proper engineer with trains was too smart for his own good..... started a lecture in metric and halfway through converted everything to decimal inches so it was easier for him to work, board just changed by the time you looked back up to check you were taking down notes correctly

 

[Tinbasherdan]

Incidentally, 25mm to 5mm, is there sufficient gusseting on the back? I have visions of it peeling itself out otherwise

 

[backpurge]

He did offer to do a plate test using his mig, this is a part in tension so I want it to take at least 30t or enough to take the parent metal past its modulus of elasticity. He still reckons that it'll hold better with a mig set up how he wants haha

I need to do some uni work over the holidays with some suspension components so I may throw this one into the mix and see how much it should take based on calculations then test it in the machine when I'm back on site

I ran the stringers at 125A then the caps over the top at 120, angle of the picture doesn't show the height but I'm about 12mm up the plate to the edge of the fillet






Yeah I was welding with 1/8th 7018s on a bumper then changed to use 1/16th 6013s just to finish up a joint on a fuel tank I was making (ran out of argon for the tig) forgot to change back to 30A from 125.....that rod lasted all of three seconds


This is the piece in question anyway, before final clean up


View attachment 76436

To be honest that welding is pretty poor, all sorts of problems that need addressing

 

[BrokenBiker]

didnt realise there was a picture, i agree that welding is poor and i wouldnt try towing anything with lugs that had welds like thos around them...looks like a massive weave has gone on, much better to just put a good solid root in with a 3.2 and then put a few stringers over the top then if you want you could weave a pass over the top to tie it all in together

 

[super noob]

Incidentally, 25mm to 5mm, is there sufficient gusseting on the back? I have visions of it peeling itself out otherwise

yeah its welded to whats essentially a box section and welded through from the other side too, rectangle cut out of the plate its mounted to on the inside and then welded round the side, plate is then welded to the front plates on both inside and out

 

[super noob]

didnt realise there was a picture, i agree that welding is poor and i wouldnt try towing anything with lugs that had welds like thos around them...looks like a massive weave has gone on, much better to just put a good solid root in with a 3.2 and then put a few stringers over the top then if you want you could weave a pass over the top to tie it all in together

As I said that weave was just me seeing how wide I could actually go, I'm not using this one I was just messing about to make sure everything fitted together as theres about 15 pieces to this, I've already had to modify the cad once after finding a couple of small issues and areas where alignment tabs would help

The plate is beveled, hit with an 1/8th" rod all the way round as a root into the bevel, capped with two over the top of that and then another two to build up some extra height before I got bored and tried to see how wide I could weave with an 1/8th" rod. Turns out pretty wide is possible!

The 25mm is welded to the 5mm on the inside too as I made a cutout in the plate so I could get a single pass all the way round, it won't be coming off without a lot of force!

I think the Denison goes up to 75t so it'll get a proper workout, I've got two spare 1/2" plate eyes so if I get some extra 5mm plate I'll do a test between the two.... see how many passes it really needs to secure it

 

[Tinbasherdan]

yeah its welded to whats essentially a box section and welded through from the other side too, rectangle cut out of the plate its mounted to on the inside and then welded round the side, plate is then welded to the front plates on both inside and out

So it has a backing plate?

 

[super noob]

So it has a backing plate?

Yeah, 8mm backing on top of the 5mm plate its welded to

 

[Sarto]

Theoretical question

Between material of different thickness, isn't enugh to lay down a bead (or multipass) with a section the same size
as the thinner of the two?

Wouldn't the thinner plate fail at the same time of the weld in this case?

 

[Chris Stevens]

As I said that weave was just me seeing how wide I could actually go, I'm not using this one I was just messing about to make sure everything fitted together as theres about 15 pieces to this, I've already had to modify the cad once after finding a couple of small issues and areas where alignment tabs would help

The plate is beveled, hit with an 1/8th" rod all the way round as a root into the bevel, capped with two over the top of that and then another two to build up some extra height before I got bored and tried to see how wide I could weave with an 1/8th" rod. Turns out pretty wide is possible!

The 25mm is welded to the 5mm on the inside too as I made a cutout in the plate so I could get a single pass all the way round, it won't be coming off without a lot of force!

I think the Denison goes up to 75t so it'll get a proper workout, I've got two spare 1/2" plate eyes so if I get some extra 5mm plate I'll do a test between the two.... see how many passes it really needs to secure it

Looking at that pic, its maybe not a great image to promote the idea that MMA is superior to MIG? I have an old 200A Kemppi MIG, and am pretty sure I could produce a better weld on that job with it in less time.

MMA is probably to be preferred over MIG, if you have a hobby MIG machine, and are working with heavier material, but if you have industrial MIG, I would guess MMA is less useful?

I have 3 TIG/MMA sets, and the only time I have ever used the MMA function, is for fixing some shelves in my storage container, using very small and portable Messer MMA/TIG 160A inverter...............rods were about 10 years old, so not great looking welds!

 

[super noob]

Theoretical question

Between material of different thickness, isn't enugh to lay down a bead (or multipass) with a section the same size
as the thinner of the two?

Wouldn't the thinner plate fail at the same time of the weld in this case?

I'm happy to be corrected on this but in theory the parent metal will break first if the weld is the same thickness, its what we saw last time we tested 2mm plate tig, mig and oxy welded. The weld was about as thick as the parent metal but the area that fails is the heat affected zone on the parent metal just under/above the weld.

This is the weakest part of the structure due to the heat cycling, the grain structure gets changed and weakened

 

[super noob]

Looking at that pic, its maybe not a great image to promote the idea that MMA is superior to MIG? I have an old 200A Kemppi MIG, and am pretty sure I could produce a better weld on that job with it in less time.

MMA is probably to be preferred over MIG, if you have a hobby MIG machine, and are working with heavier material, but if you have industrial MIG, I would guess MMA is less useful?

I have 3 TIG/MMA sets, and the only time I have ever used the MMA function, is for fixing some shelves in my storage container, using very small and portable Messer MMA/TIG 160A inverter...............rods were about 10 years old, so not great looking welds!

Oh no doubt a mig could produce the same in less time, its a lot faster! But outside in a 25mph wind I wouldn't even think about dragging out the mig

I'll post up some pics after christmas once I've welded up the 1/2" plate to show how this one looked before I started messing about with how much weave I could get

I've only got single phase at home and not even a decent sized outlet! So any form of super powerful mig is out of the question.....if I had a workshop and if I could run the same 400A one at home that I've used in the past for these then I would. Once its tacked in place it takes no time at all to buzz round it

 

[Chris Stevens]

Oh no doubt a mig could produce the same in less time, its a lot faster! But outside in a 25mph wind I wouldn't even think about dragging out the mig

I'll post up some pics after christmas once I've welded up the 1/2" plate to show how this one looked before I started messing about with how much weave I could get

I've only got single phase at home and not even a decent sized outlet! So any form of super powerful mig is out of the question.....if I had a workshop and if I could run the same 400A one at home that I've used in the past for these then I would. Once its tacked in place it takes no time at all to buzz round it

Thing is have you tried to do the same sort of job with an industrial 200A Mig, running on single phase? If not then suggesting MMA will mean superior results seems to be guesswork?

 

[davidjohnperry]

Real welders are stick welders

 

[Bill Edwards]

In answer to the argument on the first post I would say the MIG fan is talking nonsense. MMA is harder to do, gives more penetration for the same amperage, will work outside (no, body shielding is not enough to keep a gas cloud in place) and is certainly no weaker.

But before setting out on a test to prove which is better, what MIG is the other person using? It's no good you running one bead along a 10mm plate with a 3.2mm rod at 120 amps if the MIG chap is going to blast it with 250 amps for the same run.

 

[BrokenBiker]

In answer to the argument on the first post I would say the MIG fan is talking nonsense. MMA is harder to do, gives more penetration for the same amperage, will work outside (no, body shielding is not enough to keep a gas cloud in place) and is certainly no weaker.

But before setting out on a test to prove which is better, what MIG is the other person using? It's no good you running one bead along a 10mm plate with a 3.2mm rod at 120 amps if the MIG chap is going to blast it with 250 amps for the same run.

my idea for teh test was to get the mig set for 120 amps, so about 3mm ish steel with full penetration, then jump straight on the 10mm without altering anything.

 

[Bill Edwards]

Hmm, but then it isn't a fair test is it. It is (or should be) common knowledge that MIG can lay a bead down without enough heat to penetrate and trying to weld something 10mm thick with even 150 amps isn't enough, that can't be a fair test because that isn't how the process is correctly used. Unless of course you're against somebody who thinks MIG is so mighty you don't need big amps to penetrate, in which case you can ask them to prove it and then laugh!

I think the only fair way is to build up runs (or a run) of weld to the same physical size and then test?

 

[WorkshopChris]

£ 500 mig and 12mm steel doesn't sound right.
Mig can look good and strong but just be sitting on top.

 

[backpurge]

You can't compare them as the processes are not like for like, a crap weld will always be crap whatever you use and a sound weld will always be a sound weld.

 

[BrokenBiker]

You can't compare them as the processes are not like for like, a crap weld will always be crap whatever you use and a sound weld will always be a sound weld.

i think the main arguement here was that the mig monkey claimed his 500 quid mig was the better process because he thinks its harder and he knows how to use it...where as the other side of the arguement was that a cheap MMA set will give stronger welds on thicker gear than a 500 quid mig and is actually harder to use than the mig set (unless of course you picked up a 300 amp mig for 500 quid in which case give me the mig for the 10mm anyday)