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What does Duty Cycle mean in Welding

Thursday, 19th March 2020
Graham (Tech Advisor)
The Welders Warehouse Online Shop

This is a common question.  Essentially, Duty Cycle is a measure of how long a welder will operate for before it overheats and cuts out.

As some of you may prefer to watch than read, I’ve also produced a video on this subject

There are 3 key bits of data to Duty Cycle figures:

Amps, a Percentage Figure (%) and the Ambient Temperature the machine was tested in.

Unfortunately, whilst most manufacturers will state the first two figures, they often don’t state what the ambient temperature was when the test was carried out and this is actually a key piece of information! (more on this later).

An example of Duty Cycle data might be:

200amps @ 30% @ 40⁰C

This breaks down as follows:

200amps is what the machine was delivering during the test

30% is the percentage of the work period that the machine continuously delivered 200amps before overheating and cutting out. (in the UK a work period is defined as 10 minutes)

40⁰C (104⁰F) is the ambient temperature of the room when the test was carried out.  So the machines fan is cooling the machine with air that is at 40⁰C

What do these Duty Cycle numbers mean?

In our example, the machine delivered 200amps, for 3 minutes (30% of 10 minute work period), in a temperature of 40⁰C, before overheating and cutting out.

Clearly these figures are pretty specific and hardly anyone is ever going to match all the numbers.  For example, when is it ever 40⁰C here in the UK????  Clearly if the machine is being used in colder temps, the runtime (%) will increase.  Which is why it annoys me that a lot of manufacturers don’t state the ambient temperature the test was conducted in.

Here in Europe, 40⁰C (104⁰F) is the norm, BUT this is not mandatory and some manufacturers will carry out tests in 25⁰C (77⁰F) or even 20⁰C (68⁰F), which, in my view, is a bit naughty because a lower temp will make the % figure look a LOT better than a machine that’s tested in 40⁰C (104⁰F).  So beware!!!!!


The point of these numbers is to compare machines.  It’s a bit like comparing car fuel consumption, no one ever gets the Miles per Gallon the manufacturers claim the car will do, but you can use the numbers to compare makes/models.

I hope you found this blog article useful, if things work out well for you, please feel free to post some pictures of your achievements on our Facebook Page

Please let me know what you thought of this article by leaving a comment.  Don’t worry, your email address won’t be added to a database or shared and you won’t receive any unsolicited email.



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  1. Anthony Michael Beardmore says:

    Hey mate great site loving the info you share 👍👍🍻 but sorry I have a question also I have a piece of outdoor cast iron table chipped off from falling over I only have a gas less mig or solder. If I turn everything down can I weld it and will I need to buttweld it ( grind 45%and fill it with weld thankyou kindly from Australia 👍

    1. Graham says:

      Hi Anthony
      Thanks for the comment.
      Re the question, Mig is not a great process for welding cast Iron.
      You can either take a chance with the Mig, or take the table to a pro.
      Using the mig is very likely going to result in a brittle weld, so it depends on how much load the weld is likely to need to withstand.
      Keeping the weld as small as possible would be a good ideal, a V prep is also sensible.
      If you are going to risk the mig, do lots of very short welds, almost like tacks.
      But I would see what the cost of a pro would be first 😉
      Hope that helps.

  2. William Kaye says:

    Started jewellery making at 74years old.Knew a fair bit about welding(advanced amateur) but nothing much about soldering or brazing both necessary for me to know now.Found your site a massive resource of fast,concise and accurate info.Much obliged and very grateful.Really sorry about Brexit though makes buying from England a pain in the butt

    1. Graham says:

      Hi William
      Thank You for your kind and generous comments regarding the blog, much appreciated! Great to hear you found the information useful and easy to read. I feel your pain re buying from the UK, we have the same pain when we import from our EU based suppliers.
      Kind Regards

  3. John Glanville says:

    Very clear and helpful!

    1. Graham says:

      Thanks John, glad you found it useful. Regards Graham

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