If you have been welding, you know how important welding duty cycle is.
So what exactly are they?
Welding duty cycles are expressed in percentages of each 10 minutes that a welding machine can run before it automatically shuts down. For example, a 60% welding duty cycle means you can use the welding machine for 6 minutes out of every ten and rest for 4 minutes.
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 unique design of the welding machines.
There may be a few astronomically expensive, highly specialized industrial machines for welding that can operate for hours on end, but the vast majority of these 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 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.
Contents
Welding Duty Cycle in Detail
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 welding duty cycle of the particular model should also be written here by the manufacturer.
As already mentioned above, the Duty cycle means the percentage of each 10 minute period that the machine can run before it automatically shuts down.
For example, a 60% welding duty cycle means 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.
You can either weld for 2 minutes, let the machine cool for 3 minutes while you set up the next piece, and again weld for 2 more minutes, then let it cool down for another 3 minutes, and so on for a 40% welding duty cycle.
Most equipment and machines that you will work with will most likely have two different welding 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 mostly encountered only in the heaviest industrial settings.
What Happens When The Duty Cycle is Exceeded?
At the end of its welding 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 work piece for your next weld.
Importance Of Welding Duty Cycle
Duty cycles, although they seem like an inconvenience at first glance, are quite useful to you as a welder.
Of course, they perform an extremely valuable function as it is, keeping your machine from overheating and fusing into a useless hunk of metal that costs you several hundred or perhaps several thousand dollars.
You can utilize welding duty cycles in other ways as well, including:
• Raising your visor and seeing if there are any fires.
Some professional welders report that it is difficult, if not impossible, to carry out a weld without setting fire to something nearby.
Since ordinary fire is far too dim to see through a welding helmet’s visor, you can take a look around to make certain the building isn’t about to burn down around you.
• Put in a fresh welding rod if you are using a stick welder. A typical “stick” lasts for around a minute, in any case, so stick replacement will fit naturally into some duty cycles.
• Check your work and change your position for the next weld accordingly.
You may need to approach the item from a different angle, and finding the appropriate angle during the off period of the duty cycle will get you ready for when your machine is “online” again.
• Remove slag from the weld if the type of filler metal you are using necessitates this, which will drastically reduce the time taken to clean up the mess later.
• Examine the weld bead for shape and quality so that you can correct it as necessary.
Can We Reset the Welding Duty Cycle?
Do not shut off a welder during its duty cycle!
Although it might seem like turning off your welder might help it to cool down faster, the machine will stay hot longer if it is switched off amid its “cooling period”.
If you are done with the machine for the day, or an hour or two at least, then, by all means, shut it down.
However, for cooling purposes during the duty cycle, the machine must remain on.
This is because a small fan, or several small fans, move cooling air through the vitally important areas of the machine when it is on.
Shutting off the power turns these fans off as well, and lets the heat sit in the middle of the case until it gradually radiates out.
This means that, within the limitations of the duty cycle (the length of time the welding machine can keep running before it needs to shut down to cool itself off), you can weld continuously without needing to stop and reload another stick or pick up a fresh rod if you are feeding the filler metal into the pool manually.
How to Calculate the Welding Duty Cycle
There is also an exact formula that is used to calculate the welding duty cycle of a particular machine, apart from the one that is mentioned.
If you are skeptical about the duty cycle mentioned with the amount of current you are using you can use the formula to accurately calculate.
Although before directly jumping into the formula, there are some steps to follow:
- The period over which you have to calculate the welding duty cycle, the widely accepted period is 10 minutes but you can also calculate for 5 minutes as well
- The temperature of the room where the test is done.
- And whether the machine used for testing is a fresh one or has been used for. Basically, you have to check if the machine is already warm or not.
If you are done with the checks, you can now move onto the calculation part.
Welding Duty Cycle Formula
D = ( I/Iₘ )² x T
Where,
D = Required Duty Cycle [%]
I = Rated Current at the required Duty Cycle
Iₘ = Maximum Current at the required Duty Cycle
T = Rated Duty Cycle [%]
Example: 200 Ampere Power Source rated at 60% Duty Cycle and operated at 250 Ampere:
D = (200/250)² x 60 = (0.8)² x 60 = 38%
Hence, 38% is the required duty cycle calculated.
This leads us to the conclusion that the machine can operate 3.8 minutes with a current of 250 Amps(Of a 10-minute cycle).
Duty Cycles and Welding Processes
When it comes to welding, there is a huge variety of processes available to you for different base metals.
Each of the processes comes with different welding machines as well, which is always not the case since multi-process welding machines exist.
However, if you don’t know the exact duty cycle of the welding machine you are working with, you can make a rough estimate based upon the process.
TIG Welding
TIG(Tungsten Inert Gas) welding is usually used on thinner metals, which doesn’t stress the machine and thus has a duty cycle that is hard to reach.
You can essentially say that you have a 90%-100% welding duty cycle for TIG.
MIG Welding
MIG(Metal Inert Gas), Since this welding method is almost automatic it is somewhat difficult to make a right guess of MIG welding duty cycles.
It depends upon the task you are working on in the case of MIG.
If you are working in production, you might have a lower duty cycle compared to when you are working in maintenance, which does not require heavy work and thus a better duty cycle.
Stick Welding
Otherwise known as MMA Welding, it requires heavy manual work. That is the welder constantly changes the settings, electrodes and cleans off slag, etc.
Thus the welding duty cycle is not that critical and hence is usually on the higher end.
Conclusion
With this article, I tried to explain how important welding duty cycles are and how to work by it.
If you are starting out, you don’t have to worry about duty cycles, since it gets reset when you are doing other tasks.
So don’t worry.
Happy Welding!