How to mig weld part  2: Mig welding machine duty cycle

Welding duty cycle is another area that you need to be aware of, particularly if you are shopping around looking at buying a mig welder.

How to mig weld. Part 2: Mig welding duty cycle

Duty cycle is a measurement of how long you can weld for before the machine will stop from overheating. All machines will have a duty cycle rating in a percentage format. Usually this is taken over a ten minute time period, although some machines are rated using a five minute time scale. This can give you false duty cycle ratings if you are comparing two machines if one is on a ten minute time frame and on is on a five minute time frame.

The below diagram shows what duty cycle is.

As you can see in the drawing, you will have a power on period and a power off period. So this is what a particular machine is capable of, 60% on, 40% off so that it can cool down.

Then if we convert that percentage to time it would be 6 minutes continuous welding and 4 minutes for it to cool down. Then the cycle starts again and you go for another 6 mins on 4 mins off. The bigger the machine, the bigger the duty cycle. There will even be ratings for how much duty cycle at maximum power. For example a 400amp machine will be able to run at 400amps, but only continuously at say 247amps all day without overheating.

Now a 400 amp machine is a pretty big machine. But the thing is. If you are welding by hand manually and you are not using a welding tractor or a robot. You will find that you stop welding all the time anyway. This is because you might have to move along further, or you have to reposition yourself. When mig welding by hand it is no way near as consistent as when you are semi or fully automatic welding. Therefore that duty cycle rating does not mean as much to you. Because yes it's 400 amps, but how long are you going to hold your finger on the trigger at 400amps.

If comparing to a smaller machine like a single phase DIY type machine that start at the 90amp mark then duty cycle becomes a major issue. Once again if you only need to weld up some thin gauge box section here and there, or you need to weld up a lawn mower deck the welding duty cycle should not be an issue.

Often I hear stories where people have bought a new mig welder for the first time only to get it home and start using it and it cuts out because they have used up the allocated duty cycle for that particular machine. I have even heard this from manufacturer's sales reps, where one guy called up the company and they came around to the workshop. The guy said to him to start welding, and when he did the rep. started his stopwatch. When the machine cut out the rep. checked the stopwatch and said, nope that's fine there is nothing wrong with the machine and went back home. So make sure you get the most duty cycle possible that you will need.

How to mig weld. Part3. Mig welding consumables