MIG welding - beginners question.

A few weeks ago I posted a question about cheap gasless MIG welders as I was having trouble welding 1.2mm steel box section with my MMA machine. I have now bought a cheap (£150) machine and it's night and day - half an hour's practice and I'm making satisfactory welds using flux cored wire.

The hardest adaptation I had to make was trusting the machine to get the wire feed right as I'd (sort of) trained myself to keep a constant arc length with MMA. This resulted in me moving the MIG torch away from the work when it looked like the wire was going to touch the weld pool. The machine responded by squirting out more wire of course, with bad results.

I've now discovered that a 'standard' MIG process is short circuit/arc/short circuit etc, and maybe that's what the machine is trying to do. Would this be normal behaviour for a low-end MIG welder? I'm happy that it works of course, but would like to know what's going on. The manual that came with the machine is pretty much unintelligible but does refer to an 'inductance' setting which isn't explained but might be something to do with with limiting current in the short circuit phase. I'm in that foggy area where you don't even know what the right question to ask  is with this, Any elucidation welcome.

Robin

Edited By Robin Graham on 01/05/2022 02:42:43

Although I have a "gasless MIG" welder too, my knowledge of how it all works is about like yours. But it seems to work well. There are lots of YouTube videos that are helpful.

I'm not an expert either and I mainly use gas but keep a constant distance from the work and watch the puddle. If the puddle is building up increase your travel speed of reduce the feed setting.

I bought a cheap MIG welder made by Giantz in the new year sales which was a lemon and got my money back after 8 weeks haggling. Only by threatening to take my case to Consumer Affairs and post bad reviews on the internet. Now have a known brand (CIGWeld), sold here in Australia.

The wire feed speed is slower when starting an arc to build up heat for a second or 2, then speeds up to the wire setting.

And as Hooper has said, lots of Youtube training videos available.

3 typical modes in MIG welding - Short circuit, globular and spray -

Short circuit is normal for thin materials (2-6mm depending on available current), lower current ( typical of most 'home' MIG machines - 150amps and less). Least material distortion, low heat spread, a fair bit of spatter. Welding takes place by heating the wire in the short circuit past melting, etc. When working well it sound like frying bacon...

Globular , increased current, occasional short circuiting, but large globs of molten metal form on the end of the wire and are propelled by magnetic force into the weld pool - much higher current, much deeper penetration, good for out-of-place ( vertical, etc) welds. 150 amps maybe, but excels in the 180 to 220 amps region on steel and S/steel. Lots of spatter. NOT achievable with gasless machines.

Spray is big amps - 200 plus, very clean welds, the wire turns molten as it leaves the nozzle and a 'spray' of molten material is shoved into the weld pool. Sound is just a constant hiss, no snap, crackle or pop. Needs GAS , less than 15% Co2, lots or Argon, a touch of O2. VERY clean welds, deep penetration.

So, your gasless will really only do short circuit mode. Keep the torch a close to the weld as possible, MINIMUM wire stickout possible, and fry away...

ESAB has some good info ( many other sites as well - AFROX, etc..)

ESAB Welding Manual

Too tune in, for example, on 3mm mild steel, start at a setting of 100amps, with a low wire feed rate. Sit the torch cup at 45deg, touching the material and press the trigger - no need to look at the weld point, gently slide the torch away from the weld onto clean material all the time, and then adjust the feed rate with the free hand, till the bacon fries nicely. Now do a weld and see if you are obtaining the desired penetration. If not, increase FEED ONLY, till the torch starts to kick back - this is when the wire cannot melt fast enough any more and the short circuit is too rapid. Back off feed till that 'just' stops. Then increase the amps 10-20% and check again for penetration...Sounds complicated but takes 10sec at most to do.  Luckily with gasless home jobbies you are severely limited in amps and upper modes, so no globular or spray...

spelling..

Edited By Joseph Noci 1 on 01/05/2022 07:24:22

Hi Robin, this scan may help you understand what happens to your arc.

The characteristics of your stick welder are like this scan.

Regards Nick.

Edited By Nicholas Farr on 01/05/2022 08:21:40

Although there is no doubt a bottomless wealth of knowledge here, MIG welding has its own forum Here

+1 for this site covers a lot of other useful stuff as well

Thanks for replies - especially for Joseph's and Nicholas' detailed explanations of what's going on. I think I now understand things better.

Hopper - encouraging to know that you are having good results with gasless. I've looked at some YT stuff about these low-end machines, but after 10 mins of watching a guy opening a cardboard box, ( I think I'm OK with that) followed by shock that that it doesn't have a plug &c &c I begin to lose the will to live.

The main thing I was after was confirmation that the machine is meant to work in short circuit mode. I had incorrectly assumed that MIG machines were designed to maintain a constant arc length.

The welder I bought is of the 'idiot proof' type - just choose gas or gasless and wire size, twiddle the single knob to give the 'power' you want and the machine figures out volts, amps and feed. It works, at least on thin (1.2mm) steel which is all I've tried so far, I just need to get used it.

I'll have a look at the MIG site, thanks for the link Anthony.

Robin.

Edited By Robin Graham on 02/05/2022 22:05:53