Whether you are a welder or not, the words ‘duty cycle’ may hold at least a vague meaning for you. For those who are familiar with the way operations work for virtually any process, the ‘duty cycle’ might even be somewhat self-explanatory.
But what is duty cycle in welding?
The duty cycle is the term given to the percentage of time where a machine will operate and weld safely within a certain time span, at a given amperage. This is similar to ‘production cycles’ where you calculate how much output is produced on an average within a given time period, but because the duty cycle is focused on the machine rather than the output it produces, it is used to measure the safe running of the machine.
For example, a particular welding machine may have a duty cycle of 200 Amps @ 60%. This means that for every 10 minutes, the machine works safely at 200 Amps for about 6 minutes. For the remaining time – the 40% – the machine has to switch to thermal overload and let itself cool down.
What is duty cycle in welding?
Because welding machines have to deal with a lot of high temperatures, they should be fitted with thermal overload protection to make sure that if the temperature gets too much, it will automatically turn itself off to prevent damage to any of its critical internal components. Once the machine reaches lower, cooler, safer temperatures, it will restart.
Duty cycle changes at different amperages.
For example, for the machine we mentioned earlier, if the amperage was 100 Amps instead of 200, not only will the duty cycle increase, but it will do so non-proportionally. By reducing amperage, you reduce the likelihood of the machine heating up too fast, thereby increasing your duty cycle.
How to calculate duty cycle
The duty cycle is fairly easy to calculate.
You have only to see how long the machine remained ‘on’ when being tested and state it as a percentage. However, some variables do step into the equation to change the outcome.
The period over which the machine was tested can make a difference. Most often, the test runs for 5 or 10 minutes, but because 10 minutes is more demanding, the duty cycle may be lower for such tests.
The ambient atmosphere in which the test was carried out also has an effect. In higher ambient temperature, the machine will get warmer faster.
The final variable is whether the test was carried out with a ‘fresh’ machine or one already warmed from having been used. Unsurprisingly, testing a machine already hot will be much harsher on its cooling system than one that is cold.
The European Standard is the most widely accepted one for testing the duty cycles of machinery since it is demanding and considers the machine’s performance in ‘real-life’ conditions as compared to those of a controlled environment.
Using duty cycles to judge the performance of a machine
Given all of that, is using the duty cycle to judge how well a machine performs a good idea? The answer isn’t quite as simple as a yes or no.
While the duty cycle does give a fair idea of how well you’d be able to work with a machine, the idea is not understood by many people. The duty cycle is not about ‘the time it will work,’ nor is it entirely about output and capacity.
While there is a correlation the duty cycle can only be relied on as a judgment criterion if it is accurate and not overstated, as in many situations.
On its own, the duty cycle of a machine is not enough to make any statement regarding the productivity of a machine. Just like you would not assess the quality of a car based on the fastest speed at which it can run, you cannot assess the quality of a welding machine based on its duty cycle, since there are many other factors for you to consider when picking out a machine.
Consider that the welding process itself may affect the importance of a duty cycle. For example, in MIG welding, it can be a significant factor, whereas in TIG or stick welding, it is much less important.
Other important parts of the welding machine to consider when judging quality would include the power supply, efficiency, etc. Some machines are made to handle and run on a much lower power supply than it can handle.
For example, a machine could be able to operate on much higher amperage but are capped at 10A.
If the amperage were higher, the machine could have a different duty cycle. This power supply also puts a cap or a ‘ceiling’ on the duty cycle and restricts it.
Therefore, you can never be sure where the duty cycle is a good standard for judgment or not. More than the duty cycle, machines are better judged based on their efficiency – a mixture of higher output and a better duty cycle within the same level of power input.
The duty cycle is just another way to judge one side of the efficiency of a machine, so it is better to just focus on efficiency instead of a factor with so many variables.
Duty cycle is important though, and while it may seem on the surface like just a time-limit placed on how long you can weld with the machine, you might realize later on that by running a machine for longer than its suggested duty cycle, your weld decreases in quality and might become stiffer and agitated.
Not just that, but it can also be dangerous since a machine left running for too long can catch on fire and cause harm. Quality machines turn off on their own, however, so if you are using a good one, you’ll be safe.
Duty cycle and MIG welding
The duty cycle plays a much more important role in MIG welding than it does with other kinds of welding. This may be because MIG welding is an automatic process, with the filler metal being fed in automatically.
Thus, a MIG operator can weld for a longer while than to pause for off or downtime between welds to feed in the filler metal or carry out any other tasks.
This would depend on the specific situation, but where a welding station is set up to maximize the ‘welding time’ of a machine, the duty cycle becomes very important, especially in terms of production. For such cases, picking out a machine that has ‘too much’ of a duty cycle is better than one that is just barely enough.
Now, you can weld more efficiently with a machine capable of a much higher duty cycle and get the leverage you need to make sure nothing goes wrong during the process.
While production would involve a lot of welding, this is not the case with maintenance applications. Since the welding time is so low for maintenance, the duty cycle may not be very important.
Often, only a few welds are needed to complete maintenance. Sometimes, the welder may also take breaks and complete other tasks between welds.
What does a 60% duty cycle mean?
A 60% duty cycle means that within any period of time, you can safely run your welding machine for up to 60% of that time period at a certain amperage. Usually, during testing, this percentage is calculated by running a machine for 5 to 10 minutes.
What is a good duty cycle?
A ‘good’ duty cycle will depend on the welding process, the welder, and the specific settings for the machine. Because the duty cycle holds different degrees of importance in different tasks and varies depending on amperage, etc. there is no ‘one’ good duty cycle.
What factors affect the duty cycle?
The duty cycle is affected by several factors, such as the amperage and voltage – though voltage rarely is considered. Both the ambient temperature and ventilation are important. A machine-backed against a wall will have less airflow generated by the fan, and without the proper airflow, a machine will warm up faster and cool down slower, affecting the duty cycle.