Thread: Me and MIG

Originally Posted by Karl Robbers

Migs are largely tuned by sound and the sound we are after is a crisp crackle, like bacon frying in a nice hot pan, if it sounds like a machine gun, crack crack crack, then that will probably be too much wire and if we get the hissing sound, that will be too much voltage.

I think the best way to hear this is just to adjust the wire feed while you are welding.

Originally Posted by Karl Robbers

but a mig can and will produce a butter smooth weld that looks like it grew there, but holds nothing due to incorrect setup and/or technique. Pretty sobering when you consider that weld may be holding the drawbar of a 3 tonne trailer at 100Kmh.

I knew this but didnt realise just how bad it could be until a former employers' post supports started to fail(one on top of a BMW so the story went). Now it was 1.2mm tube on to 5mm plate and zinc plated. The welds looked great but on some of the longer supports(about 18") if you fixed the plate in a vice you could peel the tube/weld off with one hand!


Stuart

Just re-read your first couple of posts and picked up the gas type you're using, my previous experience of using argosheild light is that I'd never use it again, reasons being is that the mix doesn't allow it to run hot which describes some of the points you've raised. It just doesn't allow good penetration particularly when you're welding 3mm or more and explains the fat tacks you're getting as it just won't you to get that instant heat or burn into the material.

Originally Posted by WelderMick

Hey thanks Karl - great response
Great info there Karl. Regarding sound - the way it was running for me was a pretty constant but loud rapid crackle, so I figured it was running pretty well. That's an interesting point about cranking up both the feed and the voltage, my inclination was to turn down the wire feed and move slower. As I said, I haven't had much of a chance to experiment, but I'll definitely be trying that. I've got some 8mm plate lying around, so I'll experiment with that. Probably won't be for a few days now as there's some busy days ahead, but I'll post a few pics when done. I'd really appreciate your advice regarding what was happening with some of the overhead welds - where the wire would melt back in a blob all at once, then the arc would stutter and the wire would then push back against the job as you described. What would be causing the sudden wire melt back? These were 4F fillets. Probably 8-10mm of stickout, earth was grounded cleanly to the job. It seemed to happen in the last third of a pretty short (3-4cm) weld and I wasn't aware of any change in gun angle or anything else. It happened 3 times out of 8 welds. The other welds I was pretty happy with. [edit]. Also with these, I was 'pushing', with a lead angle pretty close to 90 degrees from the weld (maybe 5 deg tilt back), and and just a fraction more vertical than if exactly bisecting the fillet, if that makes sense.

I would be inclined to suggest a wire feed problem causing the wire to slow down therefore allowing the arc to burn back to the tip. This could be as simple as kinking the lead or twisting the gun at a sharp angle without realising.

I've heard that about MIG before, so have been wary about penetration from the start. I'm pretty confident on that front at least. I've noticed in previous posts you are a great advocate of stick and couldn't agree more with your reasoning.
I am a great advocate for stick due to its simpler process and reliability.
Migs are often sold and purchased by the unknowing as a foolproof tool that will weld a joint by just shaking the gun in the general direction of the joint. No welder does that. There is a fashion cycle being applied to welding machines these days, horror of horrors. An AC transformer stick welder will never do, no it will have to be a DC inverter with all the bells and whistles, of course this will only do if you cannot find yourslf a Mig, preferably an inverter with pulse. But if you are really serious you will want an AC/DC inverter tig with pulse and a foot control.
Don't get me wrong, I accept that there are advantages and improvements to be had with these welders, but they don't actually do a whole lot that hasn't been done in the past using good knowledge and technique.

Cheers

- Mick

I actually own a mig and use it regularly, but there are times when the only tool I would consider is a stick welder, they are just so versatile and will get the job done reliably when the chips are down.

Originally Posted by Stustoys

I think the best way to hear this is just to adjust the wire feed while you are welding.Stuart

I think I'll try that it my experimenting.

Originally Posted by DJ's Timber

Just re-read your first couple of posts and picked up the gas type you're using, my previous experience of using argosheild light is that I'd never use it again, reasons being is that the mix doesn't allow it to run hot which describes some of the points you've raised. It just doesn't allow good penetration particularly when you're welding 3mm or more and explains the fat tacks you're getting as it just won't you to get that instant heat or burn into the material.

Interesting! I thought it was the good stuff? I did read this some time ago: MIG Welding Gas Comparison. It definitely appears it is optimised for thin materials. Having said that, I'd regard 2mm as pretty thin.

I tried your aim to miss and roll technique, which is pretty fool proof, but didn't exactly give the control I was after. I'm more inclined to think it is operator error at this stage, so I'll keep experimenting.

Originally Posted by Karl Robbers

I would be inclined to suggest a wire feed problem causing the wire to slow down therefore allowing the arc to burn back to the tip. This could be as simple as kinking the lead or twisting the gun at a sharp angle without realising.

OK I'll keep an eye out for that. Seeing it was overhead, I don't think the cable was kinked, but maybe. Maybe I didn't have the feed roller on tight enough. I'll have to see if I can replicate it and pay more attention. One of the issues I did note was the zinc and crap was crudding up the nozzle pretty quickly, so gas flow and arc became erratic, but I had ruled that problem out for these particular welds.

Originally Posted by Karl Robbers

But if you are really serious you will want an AC/DC inverter tig with pulse and a foot control.
Don't get me wrong, I accept that there are advantages and improvements to be had with these welders, but they don't actually do a whole lot that hasn't been done in the past using good knowledge and technique.

No no... if you wanted to be serious you would only settle for 2% lanthanated.

Thanks for posting your experiences with the MIG, all regular things we experience. I agree that the bits of stuttering on your overheads was probably feed problems and could very well just be a minor tweak of the wire feed tension and watch your cable bends not too contorted.
I try to end my welds on the tacks and I am no pro so for better or worse it seems to help avoid those lumpy welds, so I will tack the corners, then weld towards the tack and finish on the tack or weld through it not depositing too much wire onto it. Seems to help avoid that lump or crater.

But yes although the synergic gives you a starting point I find I am making adjustments regularly depending on the type of weld and position, how hot the metal is etc. On my machine the setting seems OK for say a lap but I may back it off a little for a butt joint or increase it a bit for a fillet or uphill.
I do try to run as hot as I can without burning through and improve my travel speed and this is often at times a bit higher that the synergic setting. Mind you I still leave in synergic mode if the machine has it, I just crank the dial up or down and it all adjusts within the preset parameters. I do weld on basic older machines too where the adjustments are separate which is fun too to get a nice steady crackle.

With tacking too I tend to crank the machine up a bit hotter that the desired welding settings so they don't sit so high.

Anyway as I said I am no pro, just a back yarder now trying to get my head around MIG welding Aluminium. Everything that goes wrong with steel seems ten fold with Ally but getting there slowly, trial and error, hours and hours on the gun is what it needs. A joy to weld a nice bead but the horrors happen so quickly.

Stick and TIG seem so nice by comparison and I wouldn't consider good MIG work to be point and shoot by any means, settings, gas and technique all so important but it is quick and convenient for a lot of work that perhaps is not relying on test welds.

All the best with it.

Originally Posted by johncar

Thanks for posting your experiences with the MIG, all regular things we experience.

No problem and thanks for your contribution. Although I'm mainly trying to tap into the experiences of others to help me solve my issues quickly, I'm also aware that I'm bound to run into all the same issues as everyone else I figured it would be constructive to try and document that.

Originally Posted by johncar

I try to end my welds on the tacks and I am no pro so for better or worse it seems to help avoid those lumpy welds, so I will tack the corners, then weld towards the tack and finish on the tack or weld through it not depositing too much wire onto it. Seems to help avoid that lump or crater.

I know what you're saying. Yes I try to tack the corners, but that was one of my issues is the tacking wasn't that accurate with the MIG. With my Stick of TIG welding, I usually try and weld through (not over) my tacks for the sake of consistency in appearance but also ensuring consistent penetration. I'm sure I'll sort it with a bit more practice. Once I get back to the shed, my first priority is a bit of experimentation with wirefeed vs voltage.

Originally Posted by johncar

With tacking too I tend to crank the machine up a bit hotter that the desired welding settings so they don't sit so high.

When you say 'hotter' how are you achieving this? Voltage? I want hotter, with less weld deposit.

Originally Posted by johncar

Anyway as I said I am no pro, just a back yarder now trying to get my head around MIG welding Aluminium.

I do quite a bit of aluminium tig work, and have it in the back of my mind to try out aluminium MIG. It would be great to see some posts on your progress.
Cheers
- Mick

Well Mick, on the machine that I use mostly on thin tubes, 1.6 - 2mm it is not synergic so I am usually just increasing the voltage but may give a little wire speed as well, I couldn't really tell you by how much as it's sort of by feel. Just experiment with that until you are happy with your tacks. I do admit too that my side cutters are close at hand and I pretty much always snip the wire at about 45 degrees to give a sharp point and get rid of any ball formed on the end. A bit of a pain but it gets better results and less chance of a burn back to the tip. The cut end just seems to give a smoother and trouble free start for me.
If I am only momentarily pausing I don't cut the end every time, moreso if it goes cold.

I gave up on the idea of MIG welding ally with a regular style machine a while back. I decided to build a boat a couple of years back and so I was asking around to see was the cheapest option for MIG, already had the TIG and was more than happy with it.
So there were quite a few that told me yeah no worries, "any MIG will do it, just change the liner, use an oversize tip, blah blah" I asked for examples and demos but to be honest what some thought was OK, I wouldn't be happy with on my boat. I don't doubt though that there are chaps out there who can make it sing.
So I ended up just buying a pulse MIG and be done with it. Even though it is purpose made it is still no walk in the park to get good consistent results, it is fussy metal.
I will put some pics up of bits and pieces I have done with it, just have to load them on to the computer.

Originally Posted by johncar

So I ended up just buying a pulse MIG and be done with it.

What did you get? Also with the boat is it a plate boat kit or something of your own design?
thanks for your other tips - I'll try them out.
Cheers
- Mick

The other thing I've been pondering is weld puddle visibility. Not surprisingly I've found that 'pushing' gives far better view of the weld, whereas it's much harder to get a good view of the puddle when 'pulling' given that the torch nozzle is much thicker than a stick welding rod. Same goes for downhill welding, particularly if the weld is below your eye level. Just wondering if you guys have the same issues and what strategies you use to get good puddle visibility.
Thanks
- Mick

With MIG you should always push, the idea is to let the wire force itself into the puddle.

Originally Posted by DJ's Timber

With MIG you should always push, the idea is to let the wire force itself into the puddle.

Meh. If the situation calls for it, pulling works just fine.

Originally Posted by RustyArc

Meh. If the situation calls for it, pulling works just fine.

If you google "MIG push versus pull" there's more hits than are worth reading. So probably no point in trying to settle that debate. What I was trying to describe actually was not so much the angle of the torch in relation to the direction of travel, but more the direction of travel in relation to where your eyes are. With stick welding the pulling action (and greater stick angle) means that the arc is always ahead of the slag, and therefore the way to go, so I guess the same would apply to fluxcore MIG. Similarly with downhill MIG, since the torch is angled slightly upwards (arc force vs gravity) and the direction of travel is downwards, it's logical that it's always going to be a pulling action. But with horizontal positions, I guess the technique is far more debatable.

What I was trying to get from you guys though was what little tricks do you use to make sure you get good visibility with downhill or pull welds?

Originally Posted by WelderMick

What did you get? Also with the boat is it a plate boat kit or something of your own design?
thanks for your other tips - I'll try them out.
Cheers
- Mick

Mick, I looked at different angles of building the thing, was thinking around 5 metre centre console. Searched and looked at various designs over a year or two and the odd home built boat, just couldn't find something that jumped out at me.
Was down at Origin Boats last year checking out a mate's build and while I was there one of their 5 metre boats under construction caught my eye and I asked for a price for the bare bones hot work and was quoted only a few $k more than the flat pack, was also having a health issue at the time and a bit of future uncertainty so I put a deposit down and they welded up the basic boat.
I took it over and finishing it off now.
It seemed a better solution because I believe it is a better design than I could find in a kit and it has a known brand name on the back for better resale later should I sell it.

A couple of before and after shots.
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The finishing and full fit out will be ongoing for a little while doing little things as I save a few more $$ but it is sea worthy for now.
The little bits of welding I have done on the boat have been with TIG which I feel OK with now but have a MIG job coming up when I feel I have the confidence to do it. I want to put a small raised floor/storage hatch at the bow which needs to be welded into the side sheets being the part that concerns me. The material will be 3mm checker plate onto same on floor and 4mm side sheets. Also a bait board, seat and other minor bits to build but not so worried about them.

I would still like to build one from scratch just for the hell of it but am thinking around 4 metre using 4mm bottom and sides. Probably only cost of materials holding me back after this last project.

Some pics of a couple of small practice runs with the MIG last weekend, getting better although starts a still a bit dodgy. Main concern is the long runs and controlling the heat to get good penetration, a decent looking weld without melting through the side sheet. I think I may have to invest in a voltage control on the gun, more research needed.

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That's a stylish looking boat you got there! Not a bad way to got about it too - food for thought.
Those welds looks pretty good - what sort of MIG welder did you end up getting?
- Mick