Duty Cycle getting shorter

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Yesterday I was working on a project in the driveway, so I pulled out the flux-core machine.  As the day progressed, I noticed that my duty cycle was getting shorter and shorter.  So I thought about a few things:1>  Could the ambient temperature have that much effect on the duty cycle?2>  Could the temperature sensor be going bad?3>  Can a cooling fan be placed inside the case to cool the transformer?  Is it bad to "trick" the sensor with a fan?
Reply:Originally Posted by JC'sWeldingYesterday I was working on a project in the driveway, so I pulled out the flux-core machine.  As the day progressed, I noticed that my duty cycle was getting shorter and shorter.  So I thought about a few things:1>  Could the ambient temperature have that much effect on the duty cycle?*****Since it's air cooled--absolutely. Direct exposure to hot sun and/or receiving hot heat from contact with concrete/asphalt may place the welder's temp.--hotter than ambient.        What you're experiencing is normal on limited capacity machines.2>  Could the temperature sensor be going bad?       *****only way to determine that would be to test it per the factory recco's.3>  Can a cooling fan be placed inside the case to cool the transformer?  Is it bad to "trick" the sensor with a fan?
Reply:The duty cycle of the machine isn't the ONLY thing to consider.Some machines may have a gun and cable that have duty cycles similar to the transformer.Extending the machine's duty cycle -may- over heat these items.Machine designed to use a fan, have the airflow carefully designed to cool all around the transformer, and any other parts that get hot.  Simply cutting a hole in the case and screwing in a fan may not be the best idea.
Reply:When you said you noticed that your duty cycle was getting shorter and shorter, was the machine actually cutting out, like a thermal protector was kicking in?If the machine was sitting in your driveway, sun beating down on the case, ambient temperature going up throughout the day, then perhaps yes.  The thermal cut-off inside the welder is probably designed to protect the weakest link in the system.  If the ambient temp inside the case gets too high, maybe it was tripping earlier than necessary.  You don't mention what the welder is, or what you were welding on, what the machine settings were, so it's tough to say anything for certain....If you're demanding 100% of the machines output, the duty cycle could be relatively small.  Few people can afford machines with 100% duty cycle at 100% output.  Welding long joints with flux core wire could easily exceed the duty cycle on most hobbiest machines.Direct sunlight on a hot summer afternoon will just slow the cool down of the machine. Originally Posted by JC'sWeldingYesterday I was working on a project in the driveway, so I pulled out the flux-core machine.  As the day progressed, I noticed that my duty cycle was getting shorter and shorter.  So I thought about a few things:1>  Could the ambient temperature have that much effect on the duty cycle?2>  Could the temperature sensor be going bad?3>  Can a cooling fan be placed inside the case to cool the transformer?  Is it bad to "trick" the sensor with a fan?
Reply:My flux-core is just a HF Dual-Mig 131.  I was only running about 55 amps, not the highest settings, wire speed around 3, using .030 wire.  I was making some modifications to a trailer (adding a ladder rack, a gas can rack).  It WAS in direct sun some of the times.  Yes, it was the thermal cut-off clicking in.  Usually at those settings, I can run about 7-10 1 inch beads, but as the day progressed, I was only getting about 3.  There was plenty of time in between, as I am a freak about prepping joints, and grinding down.
Reply:The 131 has no fan, so the heat builds up in the case, like a little oven.If the Thermal cutout is at 200 degrees and the welder is 160 degrees from setting in the sun, you only have 40 degrees of temp rise to play with.A 117v muffin fan would really help your duty cycle, and they used to have some fan terminals on the back of the power switch.
Reply:If you keep tripping it out it may eventually burn the whole thing up.Kinda like jump starting with too small of a battery charger.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by JC'sWeldingMy flux-core is just a HF Dual-Mig 131.  I was only running about 55 amps, not the highest settings, wire speed around 3, using .030 wire.  I was making some modifications to a trailer (adding a ladder rack, a gas can rack).  It WAS in direct sun some of the times.  Yes, it was the thermal cut-off clicking in.  Usually at those settings, I can run about 7-10 1 inch beads, but as the day progressed, I was only getting about 3.  There was plenty of time in between, as I am a freak about prepping joints, and grinding down.
Reply:JC, up grading to a cooling fan is the way to go. Look at Digikey.com for fans. Match the AC voltage and choose something with a air high flow. Wire the fan so it is ON all the time and if the unit shuts down, keep it powered on to keep the fan running. Some photos would help us help you placing the fan.
Reply:Thanks everyone.
Reply:You have no idea how difficult it was for me not to make a viagra joke in this thread. I've never looked at the inside of one of these units, but you might be able to find a heat sink at a computer parts store that could help dissipate the heat faster, especially if you install a case fan as has been mentioned.  If the overheating part/parts already has heat sinks/fins attached, this might be more difficult.Something like this stuck to the transformer is what I'm thinking of..Of course, you could always go a bit crazy...Or, of course, go completely nuts and install a liquid transformer cooler.
Reply:I think Billy hit it on the head.  I would run 3 beads, needing 4.  As soon as the thermal allowed, I would run that 4th.  I wasn't giving it time to really cool down.  Duty cycle usually isn't a problem for me, because like I said, I spend more time on prep.  But for some reason, that day was particulary difficult.  I am going to look for a suitable fan, and when I get a chance, I will shoot a picture of the inside of this machine.  I like this machine for flux-core.  It has been running for several years and I have never had a problem with it.  Although now I think I need to go make an unrelated post in the HF section.  See you there!
Reply:I think every time you trip the hi temp sensor it trips a llitle easier next time just like you said.  In time it won't work for sh*t.  You need a bigger machine.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I was thinking about one of these.http://www.allelectronics.com/make-a...ARING/-/1.html
Reply:120 CFM?!  A lot of lawn blowers don't put out that much.
Reply:This is a plasma cutter that was convection cooled.  I was cuting A LOT of 1/4" woven wire.  The machine got hot and sparks came out.  I took the top off and SAW the transformer coil had gotten so hot it slid down the pole piece and shorted to the laminates.  I flipped the machine over while it was hot and slid the coil back into place.  Once it cooled down, the coil would not move, so I put that fan on it.  Its a 22volt furnace fan wired on the slowest speed.  It vents out the bottom.  If you want to sweep the floor, just plug it in and roll it around the floor.  I still works fine.Yes, I cut the hole in the top for the fan with the plasma cutter.  No the top was not on the machine.I now have a bigger plasma DavidLast edited by David R; 06-09-2009 at 07:17 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Looks like an old Linde or L-TECIF IT WORKS, DON'T FIX IT2 Lincoln CV-300 / LN-7 GMALinde-VI 253,400 & 450 w/MIG35 feedersCNC Table with Oxweld O/A & Hypertherm 1250G3Lincoln Ranger GXT 250Hobart-MicroWire 300ESAB Heliarc 161ESAB-Mobilemaster 2 CC/CV Feeders& more
Reply:It weighs 200+ pounds.  I used to load it on my truck width ramps.  I think its a Linde, 30 amps in , 30 amps out.  I can cut 3/8" better and faster with a torch.  It has a PT31XL torch which is the same as some of the chineese ones have now so consumables are now dirt cheap.I now have a Hypertherm 600.  What a difference.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Yep  plasma technology in the last few years has been very much like computers in the mid 90's.   I for 1 am sold that at least on the entry level air plasmas Up through the HT1650 G3 size.  Hypertherm is the one to own,I just bought a HT1250 to mount on my CNC burning table.   I had it hooked up over the weekend using a hand torch on it.   WOW  The last plasma cutter I used was about 4 years ago & was one of Thermal Dynamics Packmaster series.  It to is an 80A out machine.  This new HT 80A er will run circles around the packmaster.    I'm sure TD's tech has evolved too.  But I believe, at least for right now Hypertherm has the biggest bang for the buck.IF IT WORKS, DON'T FIX IT2 Lincoln CV-300 / LN-7 GMALinde-VI 253,400 & 450 w/MIG35 feedersCNC Table with Oxweld O/A & Hypertherm 1250G3Lincoln Ranger GXT 250Hobart-MicroWire 300ESAB Heliarc 161ESAB-Mobilemaster 2 CC/CV Feeders& more
Reply:Time...it needs time.Your taxing the welder.If you do alot of this get a bigger welder, may not be what you want to hear.
Reply:Remember this thread?  Well, I was helping a frind fab up some stuff for his 4x4.  I was using the heck out of my machine, and kept getting the thermal cut off.   We grabbed one of those Stanly squirrel cage fans and put it so it blows right into the case.  It never quit again, never got hot, neither did the stinger.  So, now I just need to find a decent fan.
Reply:Originally Posted by JC'sWeldingRemember this thread?  Well, I was helping a frind fab up some stuff for his 4x4.  I was using the heck out of my machine, and kept getting the thermal cut off.   We grabbed one of those Stanly squirrel cage fans and put it so it blows right into the case.  It never quit again, never got hot, neither did the stinger.  So, now I just need to find a decent fan.
Reply:I would consider a muffin fan of the right voltage form another model or from a different brand welder wired to be on at all times. A fan for a PC would be too small. The heat sink on the transformer, while being a good idea will not work. In order for any heat sink to effectively remove heat, it must be in direct contact, no air-gaps and most of the heat is generated in the copper winding not the core.