how long to shut down on PM205

[www]

I often like to turn my PM205 off after welding just to have some quiet in the shop between welds or during clamp up and prep time. How long do I have to wait after tig welding before turning the unit off? I am assuming its good to leave the fan and power left on for a bit after welding?
......wayne

[performance]

Wayne, it is not a good idea to turn the welder off between welds...as this is part of your duty cycle. IF you are done for the day, its okay to turn it off after you use it, depending upon how hard you were pushing it. If you were maxing it out, then leave it on for 5 minutes or so.

[www]

Thanks Mark...........how I have been treating the time I leave it on after welds is about equal to the time I have spent on my last bead. Sounds like I should let it cool down for a bit longer. Sometimes the noise just gets to me if I need to do some thinking I will shut her down. Lets say I have a short 2 inch bead at 125 amps or so, I may only be welding for 10 seconds or so and then a bit of post flow. I would usually let it cool down for a minute or two, is this no good?

[Robert s]

This is just me but, I always turn my machines on when I am clamping and setting up. And when I am done welding or cutting I go on about my work. It may be 20min to an hour before it is shut off. And if I have a lot of welding to do for the day, I will often leave it on all day. Even if it eventually burns out the fan a $20 fan is much cheaper than a $1000 welder. And the cost of electricity to run just the fan is nothing. Love your tools and they will love you.

[DaveO]

A little math can give you the recovery time the machine requires:
((arc time) / (duty cycle %)) - (arc time)

The PM 205 duty cycle is 60% at 200 amps, for instance, meaning it can weld for 6 minutes out of 10, and needs 4 to cool off.
((6 minutes arc time) / (60%) ) - (6 minutes arc time) = 4 minutes of recovery

In the 10 second bead example at 60%,
(10 / 60%) - 10 = 6.67 seconds recovery

So in your example the "minute or two" is plenty because it exceeds the approx. 7 seconds, and because your duty cycle is likely higher at the lower amperage. But as Robert S says, it can never hurt to warm up and cool off the machine for longer periods.

[performance]

Dave,
I will qualify your answer....It's not really that simple math. The duty cycle is 60% but based off a 10 minute cycle. Europe bases theirs off a 5 minute cycle. That is significant because it does change the match. If a unit is a 100% duty cycle at 5 minutes, does not mean it is a 100% duty cycle at 10 minutes...It could be only 50% duty cycle at 10 minutes...or less...And to say a 10 minute duty cycle rating is 60% at 10 minutes does not mean it is the same for an hour rating.

[dgarnier]

if duty cycle is the amount of work time in a given span. I thick the example of 100% is throwing it off... if you have a machine the is 50% Duty Cycle for 5 minutes. Every 5 minutes you can run for 2.5 minutes of the 5 minutes. Now on a machine with a 50% Duty Cycle for 10 minutes you can run for 5 minutes of the 10 minutes. So shouldnt a machine that has a 100% duty cycle be able to run for 5 minutes in a 5 minute cycle - YES so you should then be able to run that 100% duty cycle machine for 30 minutes stright with out problems. Unless they just use the 5 minute sample to test with not account for heat build up in the machine

[performance]

Its not what you think...No, a unit rated for 100% at 10 minutes is not capable of 100% duty cycle at 30 minutes necessarily...
It is basic math, yet people don't understand that a duty cycle rating is a % OF a certain length of time...It doesn't mean that it translates to a longer period of time, proportionately...Duty cycle is NOT proportionate, and it is not necessarily linear. While a machine can operate at 50% duty cycle out of 5 minutes, yielding a 2.5 minute welding interval, before a 2.5 minute rest, it does not mean that will translate to a 5 minute period of operation before a 5 minute rest...Let's carry that out to an hour...IF a machine at 50% duty cycle on a 5 minute rating, resulting in a 2.5/2.5 minute on and off, that does NOT mean that you can operate the unit for 30 minutes with a 30 minute off period...Just doesn't make sense. IF a machine is rated for a duty cycle at a length of time, it is confined to operate within that period of time as prescribed, or you risk damage. A 100% duty cycle means that you can operate the unit solidly for 10 minutes before a break...100% is a little hard to define since there is no prescribed rest time. But all it is saying is that you can operate the unit 10 minutes before a break is prescribed...nothing more. A 10 minute rating duty cycle is defined by the 10 minute operating cycle and longer operation times though possible does not mean that it should never get a rest.

Its sort of like a prescription. If a doctor tells you to take a pill 3 times a day, that does not mean to take 3 at a time or three, spaced within one hour. They should be evenly spaced at the required interval of every 8 hours...though it is not written in stone that you can't take one at 7 and one half hours, but it should not be more than 8 for best results.

[DaveO]

Interesting- I didn't know about the European 5-minute basis or the hour basis.

I'm trying to wrap my brain around your statement: "If a unit is a 100% duty cycle at 5 minutes, does not mean it is a 100% duty cycle at 10 minutes". If I understand correctly, 100% duty cycle is the output at which the machine can operate continuously without overheating, so 100% is 100% regardless of the time basis, correct? And I'm not sure I agree that statement is true for percentages less than 100%, unless the message is "the conversion between the 5-minute basis and the 10-minute basis is not linear".

So the lesson is, know your duty cycle basis: in my ignorance of non-US, non-Canadian, and non-Australian standards (the countries I've seen represented on this board) I assumed a 10-minute basis in my post.

[Canada]

I must admit this duty cycle thing is something I apparently didn't understand either. But the 100% duty cycle is the last one we are struggling with. For me 100% duty cycle equates to no rest needed. But in reality what are the odds anyone would be able to weld 30 minutes NON STOP? Maybe with a mig and a 500 foot seam. We stop, look, replace the rod, adjust our positioning, etc. Regardless I like a high duty cycle so I will pay more to get more. Ensures that I will not over work my equipment = long service life.

[performance]

No. A unit rated for 100% duty cycle for 5 minutes may only be capable of working for 5 minutes before rest. It doesn't diminish the fact that is still capable of running for 5 minutes at 100% duty cycle...IF it is rated for 100% at 5 minutes, there is nothing to say it won't need a rest after the 6th. Our units that are rated for 60% duty cycle out of 10 minutes, could be rated for 100% duty cycle for 6 minutes.