Do You Need a Water-cooled GMAW Gun?

Water-cooled robotic GMAW guns can reduce consumable costs, downtime

For some fabricators, the choice between an air-cooled or a water-cooled robotic gas metal arc welding (GMAW) gun is simple. Some heavy-duty applications simply demand a water-cooled model because of 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, some less conventional robotic welding applications can benefit from using a water-cooled GMAW gun, too, and can contribute to much lower consumable costs and greater productivity. Water-cooled GMAW guns typically have higher duty cycles and amperages than aircooled guns, meaning they can be run for longer periods of time without stopping. A cooler gun means cooler front-end consumables. In particular, it is possible to greatly extend contact tip life with these guns compared to air-cooled models.

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 upfront costs, potential ROI, and the application specifics.

Some fabricators may choose water-cooled robotic GMAW 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 watercooled GMAW gun. For example, aluminum or heavy plate sections that have been preheated can generate substantial radiant heat that affects the cooling of the gun and can adversely affect the life of the frontend consumables. A water-cooled gun can help here.

Some water-cooled robotic GMAW guns have smaller-diameter necks than air-cooled models because optimized cooling capacity requires less copper in the neck. As a result, they can reach into tighter spaces, through complex tooling restraints, and into parts with access holes.

When deciding whether a watercooled robotic GMAW gun is the best choice, it’s important to keep in mind that these products require more maintenance and often have a higher upfront cost. It is necessary to weigh those factors against the productivity gains and savings that can result from longer consumable life.

Understanding Watercooled Guns

Keeping GMAW equipment cool is necessary to protect the power cable, gun body, neck, and consumables from damage caused by the radiant heat from the arc and the resistive heat from the electrical components in the welding circuit.

A traditional water-cooled robotic GMAW 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. Some guns are 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 GMAW 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 have much thicker copper cables and inner neck tubes, while water-cooled robotic GMAW guns have 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 GMAW 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 GMAW guns have varying duty cycle capacities 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 welding heat in a specific application are among the most important considerations when choosing a water-cooled robotic GMAW gun.

Selecting a Gun

When choosing a water-cooled robotic GMAW 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.

Through-arm robotic GMAW 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, because you need to choose the gun and associated mounting bracket to match. The robot model also determines the type of mounting hardware and gun insulation from the robot wrist you need.

As with air-cooled applications, make sure during installation that the selected water-cooled robotic GMAW gun allows proper joint access. A neck design with the proper geometry that accesses the joint with the appropriate travel and work angles can prevent poor weld quality and the need to retool 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 GMAW 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 simpler and faster to change the neck.

Water-cooled guns with this type of connection feature also have an automatic shutoff valve that shuts off the water flow anytime the neck is changed, which helps simplify routine maintenance.

Consider adding a flow switch to a system with a water-cooled robotic GMAW 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 very quickly causes a catastrophic failure.

Maintenance and Usage

Water-cooled robotic GMAW guns do require more maintenance than air-cooled models, because 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 GMAW 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 cracks or wear appears.

Using an automatic reamer or nozzle cleaning station adds significant benefits to the preventive maintenance of these guns.

A reamer eliminates the need to manually clean out the front-end consumables and can, with the addition of an automated sprayer, add antispatter 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 buildup 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 ROI

Choosing a water-cooled gun often is a necessity because of the demands of the application.

A water-cooled model requires more upfront 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 gun is a good option for your robotic application. Often a welding distributor, welding equipment manufacturer, or robotic welding system integrator can help.

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