Returning to welding after 20 years

[kabman]

Hello everyone. I've been lurking on the forum for a couple of months and picked up some great advice so far. The tutorials are brilliant.

I did a welding course at college as part of my engineering degree 20 years ago and then restored a very rusty VW camper. Since then I haven't done any welding at all and even back then I was certainly no expert. I've got a new project that requires plenty of welding so dusted off the MIG, signed away my life to BOC for a new cylinder and treated myself to a Parweld auto-dimming helmet (as recommended on here and the best 45 quid I ever spent BTW). I've been practising on some 2mm thick sheet offcuts and, once I finally sorted out the wire feed on the welder, got back into it pretty quickly. But I've got one problem that I can't seem to solve so need your advice.

It's a 120Amp welder so I have the power on maximum and the wire speed near maximum (9 out of 10 on the dial) to get reasonable penetration. I get clean looking welds and smooth control except for the first one second or so. The wire speed is too high, stubbing aginst the work, and the weld is raised and the penetration doesn't look great. Then, after a second, it gets better and the weld is nice and flat. I'm assuming it's just taking a while to get enough heat into the metal. If I turn down the wire speed it's easier to start but then the wire starts to burn back. Is there a clever trick to it?

I'm using a very old SIP Autoplus 120, .6mm wire, Argoshield light at about 10l/min.

 

[Iain Westland]

think your welder could be running right at its limit do you v the edges? and how goods your earth?

before banging your head too much though, if your using replacement panels rather than making your own then check how thick they are as a lot of the new stuff is thinner than whats on there at the moment so you might be trying to weld at too higher a need

Iain

 

[Chickenjohn]

2mm is far to thick. The only panels I've seen that are that meaty are Morris Minor inner sill steps. Most replacement panels are average 1mm thick. 1.2mm on Morris Minor sill panels for example and 0.9mm for floor panels and inner wings.

Panels for modern cars are often only 0.7mm or less thick.

Get some 0.8mm steel pieces and start practicsing.

I also think you might need a new torch liner from the sound of the wire speed problems.

 

[malcolm]

The weld does tend to start cold, though it does sound like your volt settings are a bit low for the steel thickness and the wire speed too high. Try turning the volts up a little and you might find you start better but need to move a little faster once you've got going.

The wire speed dial will be sensitive, but it should be possible to edge it to the zone between wire hammering against the work and wire burning back. To add another thought into the mix it could also be you are holding the torch too far from the work. Needs to be very close (5mm ish).

Did you replace the liner? That would do it too. If not a nice steel liner would transform an elderly machine.

Cars are thinner, though I'd get the hang on thin metal technique on something a little thicker than 0.8mm. 1.0mm would be easier.

 

[kabman]

Thanks for those replies. I think you are all right and I may be asking a bit much of an old, low power machine. I'll get a new liner anyway, if I can find one, and I've just read a thread about the evils of extension leads Actually I'm pretty happy with the strength and appearance of the practice welds so far but need to build up some confidence before starting the job properly. A bit more practice and fine tuning will probably do it. I've just been running welds on some flat sheet so far, I'll practice some lap and butt welds next and V the edges.
I'm not going to be welding car panels (well not yet anyway), I restoring an old electric powered Austin J40 for my daughter but it needs extensive repairs to the home-made chassis. In fact it might be easier to start again from scratch. I've been more successful on thinner metal but when I stepped up to 2mm, that's when I struggled.

 

[kabman]

I took Malcolm's advice and tried holding the torch closer and ........ an instant improvement

So I made a start on the J40 chassis. It's not quite as neat as the practice pieces but I'm quite happy with it.