Judging a good weld

[pdm]

Hi

This is my first post here so Hi to everyone.

I've been doing a Stage 1 MIG welding course at the local college as a starting point in deciding whether I can do some bodywork on my car.

It's a 10 week course, 2 hours per week and so far we've done pad welds and a T Fillet weld. I am lucky enough to be using a Kempi in my booth , for voltage there is an A and B setting, then 10 stages on a stepless power dial. Wire is 10 stage stepless. We are welding 6mm steel together as it's easier (apparently ). The wire is 1mm.

We've had a video about the power/current (which I read as wire speed) and keeping them in the "working area".

Too high wire speed seems to want to try and back the torch off the piece and judders, too low seems to make a hissing sound with no crackle. Power seems to alter the heat and depth of penetration but speed of movement and closeness of tip seem to have just as much of an effect.

But there doesn't seem to me to be a big difference when settings are slightly too low and slightly too high.....

Anyway if you've got this far, here's my question....

Visually what shows me I am in the right power/current setting rather than just either side ? And IF the settings were perfect is there a way of visually telling its the technique that's off rather than the settings ?

Thanks very much
Paul

 

[GrahamGKD]

Hi Paul, Welcome to the forum - there is a little bit on the weld profile you should be looking for in the tutorial if that helps?

 

[pdm]

Thanks Graham I'll have a read of that. That sectioned photo is particularly helpful.

 

[malcolm]

On a basic MIG welder you would have one knob for volts and another for wire speed (which controls both amps and the amount of filler material). If it was a rubbish machine you'll find at each voltage setting there's only one wire speed setting that will allow something resembling a weld - the two are closely related.

The power knob on the Kemppi is likely a voltage knob that also increases the wire speed to suit the new voltage. The wire speed knob will be a fine tune for wire speed. The Kemppi will allow you to work at a range of wire speed settings.

There's no perfect wire speed setting for everything - for thin car bodywork you might want the wire speed at the low end to reduce the current, and for fillet welds you might have it slightly high to compensate for increased stickout. Otherwise I'd start off in the middle.

If you find there's too much build up of weld you might increase the voltage. If you find the wire starts burning back or there isn't enough filler material in there then reduce the voltage.

 

[Sparkey]

Malc's post says it all basicly, one small thing i'd like to add....
Your settings are personal, and they will be slightly different for each person!
Once you'll get more experience, you will learn to see, feel and hear if your settings are right!
Practise, practise!!