duty cycles and heat build-up

admin

Newb question here;So do you guys actually try to keep track of the duty cycle you are running? or do you just let it cool off once it stops or starts messing up?and a semi related question, can I potentially hurt anything by turning off my welder when the cooling fan has kicked on? My initial thought was no, but then I started thinking maybe the excess heat might transmit to something that can't take it without the fan directing were the hot air goes.
Reply:With lighter units like the Hobart 235 if you don't watch the duty cycle you WILL put it in the shop for repairs.  I burned the diodes in my LX235 by being too efficient.  I did all the fitup for a significant length of welds on 3/8 for a tractor implement.You don't need to be precise, but you do need to pay attention to duty cycle.Hobart LX235Victor 250 Oxy-Acetylene Rig (welding and cutting)Bobcat 773F-350, 1999, 4x4, 16' 10K# trailerOutdoor Wood Burner - 10 cords/year
Reply:With most welding machines it's rare to actually go over the duty cycle and trip the thermal shutdown. Unless it has a fairly low duty cycle like 20%. Usually it happens, for example, when welding two 15' beams together. But it does happen and if you trip the protect you ought to slow down a bit for the rest of the day.   Some brands tend to be more heat-intolerant than others. //coughcoughChinacoughcough.//I've never burnt up a machine that way, personally. but then, unlike a lot of people on this forum, I don't pinch pennies when it comes to the tools that make me money. I buy power supplies that I'm confident will be up to the task.It's rare that a welder would spend more than like 20 minutes out of an hour "on-arc." The rest of the time is taken up moving around, inspecting your welds, chipping slag, adjusting your equipment, fetching more electrodes, grinding......etc.I've never heard that turning a power supply off while the fan is running would harm it.Last edited by Joshfromsaltlake; 07-24-2012 at 07:38 AM.
Reply:Most machines with thermal cutouts are well past the duty cycle when the machine shuts itself off. If you run to many times until it stops, you will damage the machine and one time it will simply stop and never be right afterwards. If the fan comes on, chances are that the temps are too high for the interior components. I always leave mine on until the fan stops, otherwise it will just sit there and cook in the heat.Smaller machines tend to be more suseptable to running past the duty cycle, and usually don't have the components designed to handle the excess heat..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:It bit me when I spent a lot of time doing the prep and fit-up so that I could weld uninterrupted.  The LX235 has a 20% duty cycle at full power - I had it at max, burning 5/32 rod.If I had taken the normal approach and done the fit-up in stages between weld beads I wouldn't have had a problem.Hobart LX235Victor 250 Oxy-Acetylene Rig (welding and cutting)Bobcat 773F-350, 1999, 4x4, 16' 10K# trailerOutdoor Wood Burner - 10 cords/year
Reply:The reason the question came about because I was doing some spray with my MM252. The set-up was; 29.5v(max setting), 500ipm of .035 with 90/10. At 250 amps, the machine has a 40% duty cycle. I wasn't welding for hours on end, but I was probably over the duty cycle at times. At least I didn't melt any plastic parts on the cheap Miller gun this time. I have never hit the thermal overload or had a drop off in performance that I noticed.I know I am doing the gun no favors, and I can handle the thought that I might need to upgrade it down the road. The main thing is I don't want to hurt the welder. I probably don't use it near enough to burn it up under the 3 year, but I don't want to be scrapping it in 10 years either. I want the welder to last my lifetime or more.
Reply:Originally Posted by JoshfromsaltlakeIt's rare that a welder would spend more than like 20 minutes out of an hour "on-arc." The rest of the time is taken up moving around, inspecting your welds, chipping slag, adjusting your equipment, fetching more electrodes, grinding......etc.
Reply:Honestly I have never exceeded the duty cycle on any welder that I have used. (I'll be pushing the limits of my thermal arc here soon though) I usually weld materials in the 1/8 thick range and run about 100-120 amps and can do so all day long my fabricator 252i has a duty cycle of 100% at 150 amps. And I think it's 40% at max power (250amps) again I have not come close to hitting a duty cycle, but I may in a few short weeks, as i have s job coming that will require 384 inchs of weld joining two 1/2 plates  as s fillet weld. And it requires 3 passes so that's 1152 inches of total welding. That's going to suck.Offering CNC Plasma cutting and welding projects.Follow me on facebook https://www.facebook.com/nobigdeal.fabSupport those that support WW.
Reply:I hit cut off twice with my TIG while building this mani. The TIG has been fine but I don't want to do it again. At least I now have a feel for how long I can weld and stop before cooking the machine.
Reply:nice intake manifold
Reply:Originally Posted by Grooand a semi related question, can I potentially hurt anything by turning off my welder when the cooling fan has kicked on? My initial thought was no, but then I started thinking maybe the excess heat might transmit to something that can't take it without the fan directing were the hot air goes.