Welding Machine Duty Cycles

    david - Posted on 08 January 2011

        People who have never welded tend to think of welding being a continuous task like mowing a lawn or knitting a sweater. However, nothing could be farther from the truth. A welder operates on a constant start-stop-start basis due to the design of welding machines.
    There may be a few astronomically expensive, highly specialized industrial welding machines that can operate for hours on end, but the vast majority of welding machines cannot operate for more than a few minutes at a time.

        The reason that welding machines do not run constantly is that they would quickly heat up and burn out their working parts. The energies and temperatures involved in welding are so extreme that the welding equipment itself is only able to stand up to it in small doses.

        Generally speaking, the bigger the machine, the longer it can weld before needing a “break”. Small, cheap machines can weld only briefly, while larger, better-engineered models (which also happen to cost a fortune) can weld for a longer period of time. However, this is generally not a problem because the actual time it takes to make a specific weld is not very long anyway. If the machine ran constantly, you would soon run out of welding to do.

    Duty cycles and what they mean

        All welding machines are rated with a “duty cycle”, which is expressed as a percentage. Nearly every welding machine has a data plate with important statistics and information about the machine bolted onto its exterior somewhere, and the duty cycle of the particular model should also be written here by the manufacturer.

        Duty cycle means the percentage of each 10 minute period that the machine can run before it automatically shuts down. A 60% duty cycle means that you can use the welding machine for 6 minutes out of every ten, while a 40% duty cycle would mean that you can weld for 4 minutes out of every ten. The minutes do not need to be taken in one continuous section; for example, with a 40% duty cycle, you could weld for 2 minutes, let the machine cool for 3 minutes while you set up the next piece, weld for 2 more minutes, then let the machine cool for 3 minutes, and so on.

        Most machines that you are likely to be using have two different duty cycles – a 20% duty cycle at high amperage or a 60% duty cycle at low amperage. There are machines with 80% or 100% duty cycles but these are likely to be encountered only in the heaviest industrial settings.

    What happens when the duty cycle is exceeded

        At the end of its duty cycle – in other words, when it has been welding long enough to start overheating – a welding machine automatically shuts down. You do not need to shut it down manually – the device will do so on its own. While it is cooling, you can take stock to see if you set anything on fire while welding, check out the quality of your finished weld bead, and set up the workpiece for your next weld.