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6. What's the Deal with Duty Cycle?
One way of classifying a welder's "size" is by how much amperage it can generate
at a given "duty cycle." Duty cycle is the number of minutes out of a
10-minute period a welder can operate. For example, the Millermatic® 251 MIG unit can deliver 200 amps of
power at a 60 percent duty cycle. It can weld continuously at 200 amps for six minutes, and then must cool
down during the remaining four minutes to prevent overheating.
When considering duty cycle for a Stick machine, note that most Stick electrodes are
consumed in less than two minutes. Further about 80% of all Stick welding is
done with a 1/8-inch diameter electrode, which takes about one minute to
consume.
To see if a machine meets your needs, consider the following power classifications.
- Light Industrial products typically have a 20% duty cycle and a rated output of 230 amps or lower.
- Industrial products typically have a 40-60% duty cycle and a rated output of 300 amps or lower.
- Heavy Industrial products typically have a 60-100% duty cycle and a rated output of at least 300 amps.
