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 Duty Cycle of welding machines.

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Paul Lancs

Posts : 64
Join date : 2015-02-18

PostSubject: Duty Cycle of welding machines.   Sun Mar 15, 2015 11:09 pm

For those looking to buy welding plant, who don't already know, be aware of what is called the Duty Cycle of machines. This can be almost as important as total output (amps).

The Duty Cycle is a reference to how much, or how long, the machine will run at a given output. It's usually rated in percentages. This rating is viewed per 10 minutes - NOT per hour.

Let's say you have a machine of 150 amps. Sounds ok. But only if it has a fairly good duty cycle. If the duty cycle is only 20% at 150 amps then it means that it will only run for 2 minutes out of 10 before it is maxed out. So you would have to rest it for 8 minutes. Then it might have a duty cycle of 50% at 100 amps, which means it will run at that output for 5 mins out of 10. It might only have a 100% duty cycle at 70 amps, so for continuous running, that's the max output available.

You might see some machines that have what sounds like a high output (say 200 amps) and for decent money. But they might have a poor duty cycle. It would be better to get a machine of lower amps with a very good duty cycle.

As an example, my TIG welder is rated at 200 amps max output. But it has a Duty Cycle of 100% at 160 amps, which is very good. I'm not sure of the duty cycle of my MIG, off-hand - but I will check.

The Duty Cycle rating is usually always stated on a plate on the machine, along with the amps and maybe some info on voltage (input and welding volts) and stuff. On older machines, 2nd-hand, that have been knocked about a bit, the plate might be missing or obscured.

On good machines, there should be a thermal cut-out when max cycle is achieved or exceeded. Also, there might be a cooling fan that kicks in, on a thermal switch, when a certain level is reached. Again, my TIG welder has a fan that kicks in when the transformer gets to a certain heat. I always stop for 10 minutes or so when this occurs, even if the fan switches off before that.

But it's also the case that per hour (though not necessarily per 10 minutes), you won't be literally welding (burning the rods or wire). There will be edge prep, fit-up, leveling, squaring, and checking, checking, checking.

Also, it's not good (for you) to keep actually welding for long periods. Concentration and hand co-ordination and fatigue can set in. The older one becomes, the more pronounced this probably will be. And some people are more fortunate (more gifted) than others in this regard, like a lot of things in life. You might only be actually welding for 10 or 15 minutes per hour, although you might still be working for the remaining 45 or 50 minutes. Don't get too tired - that's how mistakes and accidents are caused.

But remember the Duty Cycle also. You might only be welding for 10 minutes per hour but if that 10 minutes is continuous, then the welding machine might get maxed out, just like you would by going at a high output continuously.

Apologies to anyone who already knows this. It's for welding newbies.
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Posts : 113
Join date : 2014-11-13

PostSubject: Re: Duty Cycle of welding machines.   Mon Mar 16, 2015 6:44 am

Paul!!! Awesome info. very succinct explanation, I might add. The duty cycle bit has actually been a little fuzzy around the edges for me and now makes perfect sense. Your posts are appreciated.
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Paul Lancs

Posts : 64
Join date : 2015-02-18

PostSubject: Re: Duty Cycle of welding machines.   Mon Mar 16, 2015 10:14 am

Thanks Toasty

In paragraph 9 I did of course mean a negative effect on concentration and hand co-ordination.
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Posts : 4
Join date : 2015-03-29

PostSubject: Re: Duty Cycle of welding machines.   Mon Mar 30, 2015 12:09 am

If like me you only have 130amp unit and you want to weld 1/42 or thicker. A good thing to do is preheat, a good cherry work it back to the start from approx 4". This will speed your weld up thus cutting your welding time ;-)
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Duty Cycle of welding machines.
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