Choosing according to specifications....

[stam]

... And I'm very happy to meet you!


When you need to boil an egg you need four things: a pot, some water, the gas hob and the egg of course. That was easy!
Well in my case I need to weld aluminum plates of 3-5 mm and I have to decide on what mig welder to buy...

... Some people tell me that for this kind of work I need many amps close to 180-200 or higher.
... Some others tell me that with the right cord I can pretty work with 140 amps.
Naturally these differences change the equipment as well as the budget also.

The truth is that I finally need to decide and I need your experience. My weld must be a nice looking seam and not a messy, untidy blur, so it is very important to choose the right machinery...

Thanks everyone!

 

[BrokenBiker]

right. according to the rule of thumb you need 1 amp per 1 thou of material thickness. so for 3mm you should need 120 amps, for 5mm you should need 200 amps. this isn't a dead set rule, just a starting point.

with that you also need to consider duty cycle, there is no point buying a machine that will run at 200amps if it will only do it for 8 seconds at a time then need 15 mins to cool down before it can weld again (exaggeration)

so, considering that, I would buy a 250 amp ac/dc tig welder.

 

[gordon stephenson]

I have never tried aluminium welding with mig, but from previous posts it seems a lot of practice will be required to make nice looking seam welds, One of our experienced members will reply soon I'm sure.

 

[stam]

right. according to the rule of thumb you need 1 amp per 1 thou of material thickness. so for 3mm you should need 120 amps, for 5mm you should need 200 amps. this isn't a dead set rule, just a starting point.

with that you also need to consider duty cycle, there is no point buying a machine that will run at 200amps if it will only do it for 8 seconds at a time then need 15 mins to cool down before it can weld again (exaggeration)

so, considering that, I would buy a 250 amp ac/dc tig welder.

the rule of thumb looks pretty smart but can it work for every material the same...? I think you need different amps for 3mm of steel than 3mm of aluminum.
Also I'm looking towards mig, because I am not a pro, and tig is very technical....

As for the duty cycle, you are perfectly right!

 

[BrokenBiker]

as said it is not a dead set rule but is a starting point. from what I have read and seen aluminium mig is prone to cold lap, ugly welds and issues such as wire jamming and birds nests at the roller unless you can set the feed rollers perfectly or have a spool gun/push pull gun

 

[daleyd]

There is a good tutorial on this site about setting your mig up for aluminium, well worth a read

http://www.mig-welding.co.uk/aluminium-setup.htm

and Miller website has a welding calculator which allows you to select aluminium as a material to see what amps you require.

http://www.millerwelds.com/resources/calculators/mig_solid_amperage_calculator.php

As bb said, ally welding on mig is not really the best process, particularly if you want good looking welds. (That's not to say it can't produce acceptable results, but TIG is the preferred method)

 

[stam]

@brokenbiker I will definately work with a spool gun...

@daleyd the miller calculator is very helpful but it says that for 3mm we need only 110-130 amps and as for 5mm we need 140-150 amps which seems very little... Maybe their hardware is more efficient thus meaning it needs less amps...????

 

[daleyd]

@brokenbiker I will definately work with a spool gun...

@daleyd the miller calculator is very helpful but it says that for 3mm we need only 110-130 amps and as for 5mm we need 140-150 amps which seems very little... Maybe their hardware is more efficient thus meaning it needs less amps...????

I would have thought amps is the same regardless of a miller, or any other welder - other than perhaps some fancy pants processes the physics required to melt wire x with parent metal y is pretty much the same.

As has been pointed out this can only ever be a starting point, without knowing exactly what you are welding it's impossible to give a definitive setting, and even then you would need to adjust to suit your circumstances.

Looking at the Miller calculator the required amps for aluminium is a bit less than the equivalent steel, (4.8mm steel = 180-190 amps, 4.8mm aluminium =140-150). If you were buying a welder to suit you would add a bit extra in as an adjustment factor, i.e you wouldn't buy a 150 amp machine if you knew you were likely to be welding a fair bit at 150 amps.

 

[Jim Davey]

Based on what you say you want to weld I'd be looking to buy a 200-250 machine, try and get one with the best feed system you can afford, 4x geared rollers is recommended for 'soft' wire as you get more traction with less overall pressure, this helps to reduce the amount of wrinkling you get if the feed pressure is too tight while avoiding slipping which scuffs the surface of the wire causing it to become 'gritty' and feed poorly or jam. You'll want a Teflon/plastic liner with a brass neck liner too.

Ally mig can look very nice indeed, it does however require a lot of practice and the standards of cleanliness and prep need to be much higher than you can get away with on steel if satisfactory results are to be achieved.