Water-Cooled Robotic MIG Guns Can Reduce Consumable Costs and Downtime

For some fabricators, the choice between an air-cooled or a water-cooled robotic MIG welding gun is simple. Some heavy-duty applications simply demand a water-cooled model due to the high amperage and duty cycle requirements of the job — performance requirements that would cause an air-cooled gun to quickly overheat and fail.          

However, there are other less conventional robotic welding applications that may benefit from using a water-cooled MIG gun, too, and can contribute to much lower consumable costs and greater productivity. Water-cooled MIG guns typically have higher duty cycles and amperages, meaning they can be run for longer periods of time without stopping. Cooler guns mean cooler front-end consumables. In particular, it is possible to greatly extend contact tip life with these guns compared to air-cooled models. 

 Applications that involve long arc-on times and high-amperage welding in stationary welding cells are a good candidate for water-cooled robotic MIG guns, which often come in amperages ranging from 300 to 600.
 

 

Deciding which system is the best choice involves careful analysis of several factors. In addition to amperage requirements and duty cycle, a fabricator should consider the up-front costs, potential return on investment (ROI) and the application specifics. Some fabricators may choose water-cooled robotic MIG guns based on the length of welds — the long arc-on time needed to produce these welds generates more heat in the gun. Similarly, critical start and stop points along a longer weld joint typically require a gun that can handle the extended amount of welding.

Considering the weld joint design and the material type and thickness, as well as joint access can also factor into whether to choose a water-cooled MIG gun. For example, aluminum or heavy plate sections that have been pre-heated can generate substantial radiant heat that affects the cooling of the gun and can adversely affect the life of the front-end consumables. A water-cooled gun can help here.                                                                                                
Some water-cooled robotic MIG guns have smaller diameter necks than air-cooled model due to optimized cooling capacity that requires less copper in the neck. As a result, they can reach into tighter spaces, through complex tooling restraints or into parts with access holes. When deciding whether a water-cooled robotic MIG gun is the best choice, it’s important to keep in mind that these products require more maintenance and often have a higher up-front cost.  It is necessary to weigh those factors against the productivity gains and savings that can result from longer consumable life.

Understanding water-cooled MIG guns
Keeping MIG welding equipment cool is necessary to protect the power cable, gun body, neck and consumables from damage due to the radiant heat from the arc and the resistive heat from the electrical components in the welding circuit.                                                                                   

A traditional water-cooled robotic MIG gun circulates a coolant from a radiator unit through cooling hoses inside the power cable and into the gun body and neck. The coolant returns to the radiator where the radiator’s baffling system releases the heat absorbed by the coolant. There are guns available on the market today, however, that cool only the front of the gun where heat is generated and still use an air-cooled cable. These features help save costs and eliminate potential leaks from the cable bundle where excess movements from whipping and repetitive motion create the greatest wear.

These features contrast to a completely air-cooled MIG welding system, which relies solely on the ambient air and shielding gas to dissipate heat that builds up along the length of the welding circuit. Air-cooled systems use much thicker copper cables, and inner neck tubes; water-cooled robotic MIG guns use much less copper in the power cables and thinner wall sections in the necks because the cooling solution carries away the resistive heat before it builds up.                                                                   

In general, water-cooled robotic MIG guns are beneficial for high-amperage applications and are typically available in 300 to 600 amp models. Closely related to amperage is duty cycle, which refers to the amount of time during a 10-minute cycle that the gun can operate at its rated capacity without overheating. Water-cooled robotic MIG guns can have varying duty cycle capacity depending on the manufacturer and model.                                                                                 

The amperage requirements, the length of time the arc is actually operating, and how the system will deal with the heat of welding in a specific application are among the most important considerations when choosing a water-cooled robotic MIG gun.  

Selecting a water-cooled robotic MIG gun
When choosing a water-cooled robotic MIG gun, be sure to select a product and consumables that use high quality materials that can handle high heat.

Guns on the market come in two styles: conventional and through-arm versions.Through-arm robotic MIG guns carry the cable assembly through the arm of the robot. This style can offer greater protection since the arm of the robot shields the power cable from abrasive wear and minimizes cable whipping during air moves. It’s important to know if the robotic arm is a conventional or through-arm style, so the gun and associated mounting bracket can be chosen to match. Knowing the robot model is also important for proper mounting hardware and insulating of the gun from the robot wrist.

As with air-cooled applications, make sure during installation that the selected water-cooled robotic MIG gun allows proper joint access. Having a neck design with the proper geometry that accesses the joint with the appropriate travel and work angles can prevent poor weld quality and/or the need to re-tool expensive fixtures, which could add downtime.

To make sure the cable bundle is the correct length, it’s also critical to know where the wire feeder will be located on the robot. If a cable bundle is too short, it might stretch; if it’s too long, it could interfere with opposing structures and also fail prematurely due to excess flexing.

Some water-cooled robotic MIG guns on the market have features that make them especially easy to use and to integrate into the robotic welding system. One available feature is the quarter-turn connection, which helps establish a quick and tight connection to help maintain good conductivity and prevent shielding gas leaks. Models with the quarter-turn connection feature are designed to seat the connection properly once a quarter turn is made, making it much easier and faster to change the neck.

Water-cooled robotic MIG guns with this quarter-turn connection feature also offer an automatic shutoff valve, to shut off the water flow any time the neck is changed, which helps simplify routine maintenance. Consider adding a flow switch to a system with water-cooled robotic MIG gun. These switches ensure water is flowing through the system; if the system doesn’t detect the flow of water in the gun, it will shut down and give an error message. Operating a gun without water flow will very quickly cause a catastrophic failure. All of this means added downtime and costly repairs.

Maintenance and usage tips
Water-cooled robotic MIG guns do require more maintenance than air-cooled models, since the presence of the water circuit introduces more potential issues. For example, if a hose or the neck is leaking, coolant could drip into the molten weld pool, leading to porosity and costly rework. It’s a good idea to conduct preventive maintenance each day or before the start of each shift. Just as with any welding system, it’s important to inspect a water-cooled robotic MIG gun to ensure that all consumables and connections are tight and working properly. Inspect the water lines frequently to make sure they are tight and have no leaks, and replace the O-rings when necessary (e.g., when cracks or wear appears).

Using an automatic reamer or nozzle cleaning station adds significant benefits to the preventive maintenance of water-cooled robotic MIG guns. A reamer eliminates the need to manually clean out the front-end consumables and can, with the addition of an automated sprayer, add anti-spatter compound to help extend consumable life further. This feature adds to the overall cost of the equipment, but helps increase uptime for production, with less manual intervention, and offers a solid return on investment in most robotic welding operations.

Do not fall prey to the notion that it is cheaper to use tap water in a water-cooled gun, as it can cause algae growth or mineral build-up and eventually clogging. Instead, use deionized water or the specially treated coolant solution recommended by the manufacturer. These coolants contain special additives to lubricate internal pumps and O-rings, as well as to prevent algae growth. 

Consider the return on investment
Choosing a water-cooled robotic MIG gun is often a necessity because of the demands of the application. A water-cooled model requires more up-front investment and more maintenance, but it can provide significantly longer consumable life and increased productivity from fewer consumable changeovers. Consider the various costs, specific application needs and accessibility to decide if a water-cooled robotic MIG gun offers a good option for a specific robotic application. Often a welding distributor, welding equipment manufacturer or robotic welding system integrator can help.