mig ratings V MMA ratings

[aidank]

hi all,

a question for those in the know,

we all know that welders are rated in duty cycle

i.e. 180 amps @30%
150 amps @50%
100 amps @ 100%

my question is as follows, in the real world are these ratings the same for both MIG and MMA i.e. would a MIG at 180amps weld 8mm plate whereas an MMA would only weld 6mm

the reason I ask is that MIGS use constant voltage whereas MMAs use a varying voltage and current,

does the speed of wirefeed also impact the mig, if you have the wire feed speed turned down low on the mig would the 180 at 30% become 180 @ 50%?

also from using a MIG once turned up good and hot mind you, the amount of welding that you would get done in 3mins would be equivalent to that you would get done in 5mins with the MMA?

thanks,
aidan

 

[irondarren]

a few interesting questions.
duty cycle has nothing to do with the thickness of material it can weld, its just the welding time in a 10 minute cycle, V the overheating time or down time because of over heating.
My own personal opinion is Amp for Amp MMA will weld thicker material.
Migs are almost always CV or constant voltage, its the wire feed that actually controls the amps. The faster the wire speed the more amps going into the weld. The power settings on a Mig control the voltage. There is a sweet spot or a balance of Amps V voltage, where you get a nice weld out side that sweet spot and the result is a poor weld. As the voltage increase, then the wire feed can increase to meet the sweet spot.
If your asking for a speed comparison between Mig and MMA, mig wins hands down. You put a 15kg roll of wire on a mig and a fresh bottle of gas, and weld until one runs out. then you have to stop to change either. The only thing that would make you stop welding is because the welder over heats due to low duty cycle. With MMA you get a welding rod 300mm or 450mm long, you weld with it until its all gone. Then chip of the slag, put another rod in the holder and away you go. But slag removal and rod change is down time that you cant weld.

 

[aero]

With MMA the rod type has an effect on depth of penetration of the weld as well as the amps.

When working out amps for MMA I use either 40 amps per mm (or 4 amps per 0.1) OR 1 amp per thousandth inch, depending on if I have my metric or imperial head on.

When setting up my MIG I use the chart that came with it as the power controls don't readily relate to anything.

 

[shenion]

You need to consider the transfer mode for MIG. Short arc MIG has less penetration than MMA. It is also a lower voltage. So at the same current, the power (heat) is less.

Spray transfer MIG has a higher voltage than most MMA, so the power/heat is higher. Some here have said it has higher penetration than MMA. Spray transfer will also be much more productive as short arc (at least 2x).

Then you have dual-shield and flux-core MIG, both add additional heat.

MMA has many variables on rod types, polarity, arc length and technique.

As for the wire speed, that controls the current and the duty cycle of the arc (not the duty cycle of the machine.) The arc duty cycle is the % of time the wire is actually touching the weld pool. Technique also effect current (long stick out will reduce current somewhat.)

The 180A % 30% is the actual current. You can hit the same current with a lower voltage and higher wire sped or a higher voltage and lower wire speed (the wire speed does have a limited working range.) MIG welders duty cycle is almost completely dependent on the current. The wire size effects the current directly too.

 

[leew845]

new to this so sorry if i am in the wrong section,i really am in desperate need of a mig welder must be single phase and at least 130a and needs to be cheap my missis is on my case to get these gates done and she doin my head in ha ha please help me somebody

 

[English Steve]

There was a 130amp mig in the 'For Sale' section - don't know if it's still available. You could also put a post in the 'Wanted' section - you'll probably get more relies in there (one of the mods may move this thread into that section shortly).