Let’s begin by understanding duty cycle. We all know what it is, but just for a quick refresh: Duty cycle is a rating measurement of 10 minute increments using CO2 gas. So, if we take a 350 amp gun as an example – that means at it’s maximum it can weld 10 minutes at 350 amps with a constant current using CO2 gas.
Now take into consideration factors that affect duty cycle. Argon base gas – which mixes Argon at 75% and CO2 at 25% won't cool a gun like 100% CO2. Many other gas mixes are used in welding beyondf those two mixes, such as Argon 90/10 and Argon 95/5. Pulse is yet another factor that lowers your duty cycle.
There’s also the consideration of constant voltage. Constant Voltage, or Current, is used in MIG welding. Polarity – the direction the current flow goes can be either Straight or Reverse in nature. In MIG welding, you use Reverse Polarity Constant Voltage. In this process, the heat produced is created on the ground side of the work, while the nozzle and the contact tip are exposed to reflected heat. In this welding process, CO2 acts as a cooling agent, with smoke acting as the filtering agent – shielding the reflected heat.
Pulse welding is the process of pulsing your weld current several times per second instead of holding it constant. Pulsing causes the arc to act like its welding hotter than it actually is. However, the torch will react like the current is at the peak of the pulses rather than the “average” as read on the current meter of the power source. That’s because the arc is starting and stopping constantly, which takes more power. Also, pulse welding creates less smoke, considerably less, in fact, and doesn’t filter the reflected heat to the nozzle and contact tip.
So, how does that lesson on welding actually affect the welding gun you may want to use?
Well, it’s all a matter of the heat you’re generating. Air-cooled MIG guns depend on thermal transfer to conduct the heat from the contact tip through the handle and into the power cable before radiating into the air. This is where the duty cycle becomes important – how much heat is generated and how fast it can be conducted and radiated? For example, aluminum power cable guns are a little better at radiating heat than copper, but are also less capable of conducting current. The nozzle is insulated, electrically and thermally from the gun and radiated heat on its own.
Water-cooled MIG guns act differently. With water-cooled (or liquid-cooled…. they all mean the same thing), these depend on water (or liquid) to transfer heat into the power cable, contact tip and the nozzle. Systematically, it is a more efficient system for cooling. Heat in the water is transferred to a radiator, into a holding tank and circulated back to the welding torch.
Looking back at the break down of gases welding styles, consider that an air cooled torch rating is reduced 40 to 50% using Argon based gases, and another 20 to 30% when pulse welding is used.
Water cooled guns, on the other hand, get a duty cycle reduction of 10% for Argon base gas, and a negligible reduction for pulse welding.
There are ample pros and cons to both welding gun types, but let’s break them down here by category, and you can decide whether you’ve fairly considered each:
Simple, power cable, handle and neck. “Plug and play” in every sense.
Less ancillary equipment costs or chemical use to keep the gun running.
The longer or hotter the weld, the bigger and heavier the torch. Nozzles and tips are always hot, and depending on the delay between welds to cool, wear due to heat overexposure.
Once maximum duty cycle has been reached once, the duty cycle next time is reduced. So you’re always spending less time welding than you could be just because of the design of the gun.
These guns are always cool. The water system will remove heat from your tips and nozzles anywhere from 30 seconds to 2 minutes after you finish welding any length of time to the point of touch. (don’t recommend welding bare handed, though!). Your nozzles and tips will also last longer – sometimes at low amperages, too long, tips may reduce ability to conduct when used too long, to the point it could damage gun.
It’s always recommended to change tips on days you weld or amount of wire used. Water-cooled guns are also surprisingly light weight; the liquid and the pressure flowing through the cable makes them somewhat buoyant. A water-cooled gun that’s 500 amp, for instance, is about the same as 350 amp air-cooled gun.
Water cooled gun is more expensive to manufacture and needs the added expense of a cooling system. Connections and fittings on the gun are easier to damage and break – mostly because there is just more opportunity to do so. Water leaks in the welding area can be messy. The thermal transfer for the nozzle is a pressed ceramic and can be broken if abused, which will reduce the efficiency of the gun.
Cooling systems that are not maintained or improperly setup can also damage the guns. Lastly, while water-cooled guns can reach amperages air-cooled guns could only dream of, it is difficult to reach that full duty cycle for 500 amp, 600 or 650 amp guns.
Water cooled guns have received a bad reputation of being maintenance problems, unjustly.
With operator training and the proper set up they’re more comfortable for the operator, increase arc on time and increase productivity.
Don't agree with my take? Then let me know your thoughts in the comment section below!