duty cycle?

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My dad was a welder so I've always known how to although not that great for lack of practice I think. Just trying to understand the duty cycle thing, it says 20% on my millermatic 135, what does that mean? 20% of what? This little machine is giving me fits but will ask those questions in the appropriate section.Thanks in advance for you help.QT
Reply:Hello QTEX, your welder has a 20% rating that is based on a 10 minute run time, 10 minutes representing 100% . For every 2 minutes of operation at full-power it will theoretically require 8 minutes of rest to keep it from overheating or causing damage to the internals. Even though that sounds like a pretty short amount of time, in the big picture it causes less problems than you might think because of things such as repositioning to get better access to a weld or any number of other stops that occur when welding. When you really notice the duty cycle issue is when you have some really long runs of weld or you are needing to make multiple passes on something to build up enough weld, in that case it can be very annoying and sometimes costly. That's why it is a good idea to either limit the welding that you do to the capability of the equipment that you have on hand or start out with equipment that has a bit of reserve. Best regards, Allanaevald
Reply:From Millers manual on that machine...Duty Cycle is percentage of 10 minutesthat unit can weld at rated loadwithout overheating.
Reply:So it is 20% when set at 135 amps assuming I read the origional post correctly.  There is probably another % number in the manual for when it is set at 100 amps, and maybe another amp number below which it is 100% duty cycle.  You might find some of that data on a tag or sticker on the machine.
Reply:Thanks for the replies, that was something I was wondering too, if I'm welding at a lower setting does it increase the duty cycle? This is the front of the machine. I bought it new about 7-8 years ago but rarely used it for just like a couple small tack welds  for all those years. Seems like it didnt work right from beginning, may have been my lack of knowing how to set it right. What does the machine do when you exceed the 2 minutes? I'm assuming its two minutes of non stop welding. Do I need to turn the machine completely off when waiting that other 8 minutes or just leave it running so the fan can cool it off? Can someone please explain the chart below, thank again. Attached ImagesLast edited by QTEX; 01-24-2012 at 08:27 AM.
Reply:Originally Posted by QTEXThanks for the replies, that was something I was wondering too, if I'm welding at a lower setting does it increase the duty cycle? This is the front of the machine. I bought it new about 7-8 years ago but rarely used it for just like a couple small tack welds  for all those years. Seems like it didnt work right from beginning, may have been my lack of knowing how to set it right. What does the machine do when you exceed the 2 minutes? I'm assuming its two minutes of non stop welding. Do I need to turn the machine completely off when waiting that other 8 minutes or just leave it running so the fan can cool it off? Can someone please explain the chart below, thank again.
Reply:Originally Posted by QTEXThanks for the replies, that was something I was wondering too, if I'm welding at a lower setting does it increase the duty cycle? This is the front of the machine. I bought it new about 7-8 years ago but rarely used it for just like a couple small tack welds  for all those years. Seems like it didnt work right from beginning, may have been my lack of knowing how to set it right. What does the machine do when you exceed the 2 minutes? I'm assuming its two minutes of non stop welding. Do I need to turn the machine completely off when waiting that other 8 minutes or just leave it running so the fan can cool it off? Can someone please explain the chart below, thank again.
Reply:So how does one know how many amps your pulling? The settings on machine are just 1 to 10 heat and wire speeds
Reply:Originally Posted by QTEXSo how does one know how many amps your pulling? The settings on machine are just 1 to 10 heat and wire speeds
Reply:Duty cycle shouldn't be worried about too much. Like trackbird said, the 20% will be averaged out pretty well for small projects. I rarely have to stop because of duty cycle.-AlexSears/Craftsman 230A Buzzy BoxSears/Craftsman 180A Buzzy BoxChicago Electric 80A InverterALL STICK...ALL THE TIME!I spent a lot of time with the square peg and round hole.
Reply:Originally Posted by ArcSpark96Duty cycle shouldn't be worried about too much. Like trackbird said, the 20% will be averaged out pretty well for small projects. I rarely have to stop because of duty cycle.
Reply:Originally Posted by QTEXSo how does one know how many amps your pulling? The settings on machine are just 1 to 10 heat and wire speeds
Reply:Originally Posted by trackbirdThat chart indicates a welder that tops out oat 135 amps and has a 20% duty cycle at 90 amps. At 135 amps it may only weld for 5% duty cycle and at 40 amps it "could" be 100% duty cycle (each manfacturer rates their machines a little different). But from that chart, all we do know is that it's 20% duty cycle at 90 amps. That's 2 minutes of continuous welding and 8 minutes resting. Leave it run so the fan can cool it. When I get done running a bead, I let the machine run for a while to cool it (even if I'm done and cleaning up, I'll let it cool for a few minutes with the fan running). If you run it beyond the duty cycle it can overheat. When it overheats it will either trip a thermal cut out switch and shut down until it cools enough and then come back on...or it will melt something internally. Most of the machines I've used (typically the 110v machines) will shut down until they cool. If the thermal protection fails you'll potentially burn up something in the machine.
Reply:Originally Posted by DSWActually Alex, with small 110v machines duty cycle is something to be concerned about. As mentioned the duty cycle when maxed is maybe 10%. That's less than 60 seconds of weld time at max output. Most small machines will still weld once you pass the duty cycle, but weld quality drops off, often because the caps get drained and can't recharge while welding past the duty cycle. However repeatedly welding once the duty cycle has been exceeded is a good way to damage the unit, and the unit can be damaged before the thermal cutout shuts down the machine.