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9 LIVES
11-07-2007, 05:36 PM
I know somewhere I read that I should not run my hobart 187 mig for more than 10 minutes welding?

Does that mean I need to shut off the unit after 10 minutes of welding to let it cool ? I usually weld for 3-4 minutes and then walk away for 5-10 minutes and let the welder sit there in the " ON " position with the fan running. Is this proper procedure for keeping the machine at a happy temperature?

Rocky D
11-07-2007, 06:14 PM
No, no, no...the 10 minutes relates to duty cycle...for example if the duty cycle is 60% then this means you can weld at maximum current wide open for 6 minutes before the thermal overload breaker kicks in and shuts off your machine for 4 minutes.

hankj
11-07-2007, 06:24 PM
It's like Rocky said, but I wouldn't worry too much about it. The worse case scenario is the theraml overload trips, but I've never had that happen on any of the three MIG machines I've owned.

I can't normally hold a position that will allow me to weld up to the duty cycle without stopping to reposition something - either me or the work!

Hank

9 LIVES
11-07-2007, 06:39 PM
Gotcha guys!

So letting it sit with the fan on is not going to hurt the machine right? :)

556man
11-07-2007, 06:58 PM
Gotcha guys!

So letting it sit with the fan on is not going to hurt the machine right? :)


That's correct. Won't hurt nothing with the fan on.

556man

1990notch
11-07-2007, 07:35 PM
Someone else correct me if I'm wrong, but I think it would be better to leave the fan on if it does overheat. That way it's drawing cold air by the transformer to cool it better. Then again, maybe the thermal switch kills power to the whole machine when it trips, but I doubt it.

tigster
11-07-2007, 08:39 PM
leaving the fan on is beneficial to the welder. it helps to cool the transformer more quickly. shutting it off when it's hot can only help to shorten its life. i leave mine on for a few minutes after my last weld, and check to see if the exiting air is cool before shutting it off. maybe i'm a bit cautious, but i like to baby my new machine.

Mr Meck
11-07-2007, 11:58 PM
9Lives, You do not want to know the run time till the 187 overheats.:) What you want to know is how long you can weld BEFORE it overheats.:D Overheating is a bad thing cause repeated overheatings cause the smoke to come out. :eek: Thus the Duty Cycle is born. First consult your manual Section 4.2. Down loadable from Hobart if necessary. I got the generic cause I do not have your machine serial number. This section explains Duty cycle and overheating. Note the bold lettering stating "Exceeding duty cycle can damage unit or gun and void warranty". :eek: You exceed the duty cycle, barge into the safety zone and overheat the welder to many times, it will let the smoke out rest assured. A chart is provided to help keep you in the duty cycle and out of overheating. For example : @ 135 amps the duty cycle is 30%. That means in a 10 minute period of time you weld for 3 minutes and don't for 7. This keeps things cool. Cool is good.:cool: Notice that at 75 amps your duty cycle is 100%. Weld all day long continuously.
By welding for 3 or 4 min and walking away leaving it run for 5 or 10 min you are utilizing a duty cycle of sorts. You should in no way turn the unit off if it does overheat as that stops the fan cooling thus creating a temperature spike.:eek:and maybe some smoke coming out.
If you are like me, once the hood is down I can't see my watch, but you could have a wall clock, look at the time, weld a bit, stop, glance at the time to get a feel for the duty cycle. Hope this helps you out. :D

hankj
11-08-2007, 01:06 AM
Mr. Meck:

I read your post with some difficulty due to my current state of sobriety, and your lack of pagination, but I think I got the gist.

My question to you, the theory you explained notwithstanding, is how often in your GMAW experience have you exceeded the duty cycle to the pont that the thermal overload has operated, and how many times have you seen a machine "let the smoke out" because of it?

Just curious, as it flies in the face of my, admittedly, meager experience, yet I've welded some pretty good projects with the MM 210, without issues, at tap 6 and 80 on the WFS running .030.

Hank

SundownIII
11-08-2007, 10:03 AM
Hank,

Mr Meck is correct in his definition of duty cycle. Duty cycle is defined as the percentage of time a machine can be operated at a particular amperage in a 10 minute period. In other words, if the machine is rated for a 40% duty cycle at 100 amps, the welder should only weld for 4 minutes in a 10 minute period, letting the machine cool for the remaining 6 minutes. Machine should remain on with fan running during the cool down period.

We all know the MM210 is a very robust machine and that Miller tends to be very conservative in their duty cycle ratings. As you have stated, most welders, due to having to reposition the work, adjust position, etc., never run up against the machine's "duty cycle". Ambient temperature also plays a big role in the actual machine's duty cycle. As the ambient temperature goes down, the duty cycle goes up and inversely, as the temperature goes up the duty cycle goes down.

I think duty cycle is much more a factor in the smaller machines where the duty cycle tends to be in the 30% range of their rated output. For the guy who's "pushing" a smaller machine, duty cycle becomes much more of an issue. For instance the MM140 is only rated at 20% duty cycle @ 90A/18VDC or 63A/21VDC whereas the MM210 is rated at 60% duty cycle @ 160A/24.5VDC.

What I find interesting is that it seems that all manufacturers rate their machines based on amp output, yet the machines only have voltage taps (or voltage adjustment) and wire feed speed (wfs). I guess they expect the user to go to the graphs and figure out how many amps they're really pulling out of the machine.:D

hankj
11-08-2007, 10:44 AM
Hank,

Mr Meck is correct in his definition of duty cycle.......

I agree. That's not the point I was trying to make. Just my opinion, but I've not seen, in the "real" world, a significant number (any, for that matter) of machines that have "let the smoke out" due to overworking past the duty cycle norms.

My point was prpbably not very well stated, but what I'm trying to say is the duty cycle is no "big deal" as far as damage to a welding machine is concerned. Thermal trips due to long weld times are few and far between, in my experience.

Sorry if I confused anyone!

Hank

Rocky D
11-08-2007, 11:35 AM
You're nit-pickin, again Hank...:D I would only add here that the duty cycle is based on running maximum welding parameters...running wide open....less than that, and the duty cycle increases percentage wise. But that's nit-pickin too.
I have tripped the TOP (thermal overload protector) many times on a MM130 at work, where I had to weld 6' of trench plate. Ya really need 100% duty cycle for long continuous welds. It's a royal PIA to have to wait for the machine to cool down.

Roger
11-08-2007, 12:53 PM
Did you wish for wish for 2nd welder during cool down?

hankj
11-08-2007, 01:16 PM
Rocky,

In your case, I don't doubt it! I still remember the pictures you posted a few years back!

Hank

MAC702
11-08-2007, 03:52 PM
No, no, no...the 10 minutes relates to duty cycle...for example if the duty cycle is 60% then this means you can weld at maximum current wide open for 6 minutes before the thermal overload breaker kicks in and shuts off your machine for 4 minutes.

Just to clarify, though I know Rocky D knows this, most machines are not rated at their maximum outputs but at a lower "rated output".

For example, my MM175 was rated at 130A for 30%, so it would be even shorter at 175A, which it is capable of doing.

And I tripped its thermal overload a few times before I got bigger machines. It stops weld output and sits there with the fan on.

BBackSoon
11-08-2007, 04:39 PM
Thanks guys, I had no idea what it meant. On my Snap-On(Century) I got a green light that tells me everything is fine. I have never seen anything else. But then again I don't usually work on anything massive and even on the large projects I weld a little, then I cut and grind the next piece and then I weld a bit again and on and on.

Also, good to know about leaving the unit on for cool down. Never have but I guess I will start.

Mr Meck
11-08-2007, 10:39 PM
Hank, I don't think you are nit picking. I have a Lincoln Square wave Tig rated 20% at 135 amps AC. Used for Al fuel tank repairs mainly. I run afoot pedal with the amp control knob turned all the way up. Works fine for tanks. However trying to fix an old Al oil pan I temped it out three times in a row. Soon as the temp light went out I was back at it again. At the third temp out I had just finished. The quaint smell of wire varnish was waifing out the vents. Pretty close but the smoke stayed in. One more over temp I feel it would have been lights out. On a warm day 85 degrees with it set to DC+ and 120 amps you can burn about 10 to 15 sticks of 1/8 before the temp light shines. I did melt the water line on a weldcraft wp 20 torch. It wasn't my fault. When replacing I found the original torch lines were reversed. Seems the water came down the power side to the torch then back to the machine. Should have been from machine to torch head retuning down the power line according to the instalstructions. Aside from the Lincoln being under powered for our needs, rest of our stuff is 400 amps + all 100% rated at max output. Going for beer and book to look up pagenation. LOL.

ace4059
11-09-2007, 01:38 AM
I understand duty cycle and all the above, but just to clarify.
When the thermal overload switch kicks in and shuts off the machine when you have exceeded your duty cycle, if you do that to many times you can still burn up your machine? I have always read that the thermal switch was to shut off the machine to keep it from burning up, thus interpreting it as a safety feature to prevent the machine from "OVER" heating and just about making it impossible to burn up. It didnt know you could still burn it up if you run it till the switch kicks in.
So what I though was you could run it till the switch kicks in and then let it cool and run it again. You are saying to run it till just before the switch kicks in (but dont keep running it till the switch kicks in), and then let it cool.

Is that a correct interpretation?

-Ryan

W8KI
11-09-2007, 07:04 AM
Ryan,

I recently picked up a HH125ez for the sake of a quick fix or as a portable loaner for my kids. Within the manual it states that if that unit hits the duty cycle flag, it will shut off. It than says to allow for it to cool for 15 minutes.
Although I have never hit my duty cycle on my other units, with this little gal it is more probable.
My view is that the 10 minutes reference is for the operator to use while welding. If the operator hits the flag, more time may be necessary in order to protect the unit - else run the eventual risk of "smoking ur machine"...
I am sure someone else will chime in but, better safe than sorry.

Rocky D
11-09-2007, 10:55 AM
...
So what I though was you could run it till the switch kicks in and then let it cool and run it again. You are saying to run it till just before the switch kicks in (but dont keep running it till the switch kicks in), and then let it cool.

Is that a correct interpretation?

-Ryan
You are trying to base the cut off on time...it's not, it's thermal...so you can't predict when the switch will cut off...run the machine till it kicks in...which will be probably never, let it cool, then start welding again. You can't run it to burn it up, because the thermal overload switch will prevent it from getting too hot. When you start welding as soon as the machine comes back to life...it will weld fine, till it gets too hot and shuts off...this is not rocket science here. You may have to wait a little longer than you did before it came back to life...but you're not going to damage the machine.

ace4059
11-09-2007, 11:39 AM
Rocky,
That is what I thought.
It was I misinterperted that some people were saying, "if you keep running your machine till it hits the duty cycle, you will burn it up"

I have only hit the duty cycle with my small HH125, and a while welding 3/8" MS at 230 amps with the tig.
But I have tried to make the thermal switch kick in on my PM 215, and with it running maxed out for 18 minutes it never did hit the duty cycle, Now the mig gun was another story.

Sberry
11-09-2007, 12:14 PM
Lots of factors come into play, I ran my little tombstone dam near as hard as it could but I was in a very cool shop, 45 degree air whistling thru it, the thing never even warm. Thats not saying it couldn't cook a diode or something local internal but it certainly doesn't heat the air. My shop is cool most of the time, ran my SP175 hard, never give it a thought and never have a problem and never feel any warm air worth a second thought. I don't usually think about duty cycle, seems there are usually enough distractions for cooling time. Only thing I ever overheat was a tig torch.

MAC702
11-09-2007, 03:44 PM
You'd generally be significantly past your duty cycle before warming to the point of tripping the thermal overload. I know I was on my MM175. That's why it takes so long to cool off when you do.

If you paid attention to the time limits, you'd never trip the overload.

You never want to RELY on the thermal trip. It's a safety that you hope works when you don't pay attention to the time.

Mr Meck
11-09-2007, 07:13 PM
Duty cycle is not something you hit. Adhering to the duty cycle keeps your machine cool. If you continually run the machine till it stops welding you are exceeding the duty cycle and entering thermal shut down. If you want to ignore a machines duty cycle and run it till it stops, go ahead. But ALL the Miller manuals I have looked at HIGHLY recommend you adhere to the duty cycle. Repeated overtemps are NOT recommended and voids warranty if so conditions are found during repair. So quit confusing duty cycle with thermal shutdown. Thanks:D
I know I referenced Miller manuals on a Hobart site. I apologize. But I would bet you 100 bucks the same cautions are to be found in the Hobart manuals as well.

Sully2
11-10-2007, 08:52 AM
As a hobbiest, thermal shutdown is something I will never worry about. Running 2 inch; 4 inch; 6 inch long passes and then ( newbie here) stopping and lifting my helmet to see if Im doing all that Im suppose to be doing, the "off time" just is just about 3-4 times longer than the "on time"....so my machines never get close to any thermal problems.

But let me ask the pro's here this question.

IF you are "usually" running into "thermal shutdowns" arent you in a way..??...using TOO SMALL a welder for the particular job? Realizing of course that a guy has to use what equipment he HAS...which may not be what he WANTS to do a job

Rocky D
11-10-2007, 10:09 AM
..
But let me ask the pro's here this question.

IF you are "usually" running into "thermal shutdowns" arent you in a way..??...using TOO SMALL a welder for the particular job? Realizing of course that a guy has to use what equipment he HAS...which may not be what he WANTS to do a job

Yep, tiz true!

Sully2
11-10-2007, 12:08 PM
Yep, tiz true!

Okie doke. Thats what I was thinking....

TEK
11-10-2007, 12:55 PM
Cary brings up a good point. You can extend the time frame some by cooling the welder with a fan. I was welding up some 4"channel door frames for my sisters tilt up bldg and all I had was a MM 130xp. Print called for 3/16 fillets and I was getting that ok but did trip the overload a couple of times on the first one. I had 4 to do so I opened the panels on the machine and set a box fan so it would blow into it, slowed down a taste, and didnt hit shutdown again. Its probably not recommended but it did work.

Mr Meck
11-10-2007, 05:28 PM
That would be a correct assesment. If you are in thermal and waiting to cool on a frequent basis, then you need a machine with a higher duty cylce.:D