The Physics of Short-Circuit MIG Welding
(How It Works and Why Settings Matter)
Short-circuit MIG welding is one of the most popular welding processes in the world — and also one of the most misunderstood.
Once you understand the physics behind it, things like:
• voltage range for short circuit mig
• Why wire size matters
• Why wire speed changes amperage
• Why spatter suddenly shows up
…it all makes more sense.
Short-circuit MIG is a high-speed electrical and thermal switching process that happens 20 to 200 times per second.
Let’s break it down in simple terms
What “Short-Circuit” Transfer Actually Means
In short-circuit MIG, the wire is not spraying metal across the arc like it is with spray transfer mig.
Instead, it does this shot circuit cycle over and over:
1. The wire actually touches the weld puddle
2. The arc goes out (dead short)
3. Current spikes during the short
4. The wire tip heats and necks down
5. The droplet pinches off
6. The arc re-ignites providing heat
7. The cycle repeats
This happens dozens to hundreds of times per second depending on several variables like settings, design of machine, inductance settings, shielding gas, etc.
So short-circuit MIG is really: A controlled, repetitive electrical short circuit that melts and transfers metal in tiny droplets as well as while wire is fusing into the puddle during the short circuit .
Wire Size matters
Rule of thumb: thinner wire for thinner metal, thicker wire for thicker metal
- .023", thru , .035” wire diameters run beautifully in short arc mode
- .023" is great for thin metal like autobody panels up to around 1/8" but also helps when welding with 115 volt mig welder off an extension cord.
- .030" is a good choice if you have to switch back and forth from thick to thin
- .035" is great for general fabrication
- .045” can also be used for short circuit mig but often results in lots of spatter unless gun angle and stick out can be tightly controlled.
Bigger wire requires more amperage to reach the same current density needed for pinch-off.
The Relationship Between Voltage and Wire Feed Speed
This is where most confusion lives.
In MIG welding:
• Voltage controls arc length
• Wire feed speed controls amperage
But they are electrically linked and they need to follow each other to an extent.
In other words you can only adjust one so far with adjust the other.
Voltage rule of thumb
Short circuit mig operates in a voltage range of around 14-24 volts...and is capable of welding anything from 22 ga (.030”) to 3/8” (.375”)
So if you think about it, 14 volts for really thin like .030” and 24 volts for 3/8”, and since 3/16” is right in the middle which is around 19 volts.
Wire speed rule of thumb:
Wire speed settings are mostly determined by both metal thickness and wire diameter. But uphill welding also affects wire speed needed.
If the machine is a recognized brand, there is usually a mig settings chart that will get you close.
If there is no chart, google "MIG settings chart" and you will find at least 5.
This simple MIG settings chart is simplified but helpful
