Mig welder duty cycle

Welding duty cycle is a measure of how much welding you can do over a set period of time before the machine overheats.

This is usually over a ten minute time frame; however some welding machines are rated with only a five minute time period. This will make comparing the duty cycle on two machines very difficult if they are both over different time periods. In fact, the machine with the lower five minute time cycle will appear to give the same or better duty cycle performance when comparing to a machine that is on the ten minute time scale.

5mins or 10min cycle?

This is a little trick that I sometimes think manufacturers do to make their machines specifications look better. You will normally see a reference down the bottom of the page in small writing saying "over a five minute time cycle", or words to that effect. The actual duty cycle rating will be on a sticker that will be on the welder somewhere. This could be on the back, on the front, the side or inside the door to where the mig wire spool goes.

The rating will be as a percentage. For example it might be 35% or 40%. This will be a percentage of time that the machine can weld for continuously until it overheats, all within that ten minutes. So if it was 35%, it means that you can weld at full power flat out for 35% of ten minutes. But what happens to the other 65% of time? Well now you have to stop for 65% of ten minutes. So that is 3.5mins on, 6.5mins off. The time that you stop is so that the machine can cool down. Most machines will have a thermal overload feature that when the unit gets too hot it will shutdown. This shutdown time is then used so that the machine can cool down.

Below is a diagram showing how mig welder duty cycle works.

Looking at this diagram above you can see that it is taken over a time period of ten minutes. You see that you can run the machine continuously for 60% or 6 minutes, and the cooling down time of 40% or 4 minutes.

Here are a couple photos of some machine specifications showing the duty cycle ratings.

As you can see in the photos, they also rate the duty cycle at specific amperages as well. This is so that you also know how many amps the machine will be at 100% duty. Whatever this figure is will be how many amps you can run the machine at all day without overheating. Also don't forget that on hot summer days the ambient temperature will be higher and the duty cycle won't be as good. Vice versa in winter, if you live somewhere where you get that cold you have snow, the duty cycle would obviously have to be much better than a machine running in the Sahara desert for example.

You also need to be aware of the duty cycle for when you buy a mig welding machine. Many people often buy a machine that is too small for the job. Even if the machine is rated at 200amps, if the duty cycle is very low you might find yourself having to wait for the machine to cool down all the time. This is a real hassle when you are trying to get the job done.

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