Reduce Downtime and Costs with Water-Cooled Robotic MIG Guns
For many fabricators, the choice between an air-cooled and water-cooled robotic MIG welding gun is easy. Their heavy-duty applications simply demand a water-cooled model due to the high amperage and duty cycle requirements of the job — an air-cooled gun would overheat and fail prematurely under such conditions.
In the right application, a water-cooled robotic MIG gun can often prove beneficial by minimizing downtime, increasing productivity and reducing consumable costs. These guns typically have higher duty cycles than air-cooled models and operate at higher amperages, which means they can run for longer periods of time.
Still, deciding whether an operation would benefit from converting to a water-cooled MIG gun involves a careful analysis of several factors. In addition to considering the amperage requirements and duty cycle, a fabricator should consider the upfront costs, potential return on investment (ROI) and the specific application.
For example, some fabricators may choose a water-cooled robotic MIG gun because of the length of their welds — they need a long arc-on time to produce long welds, which generates more heat in the gun. Similarly, critical start-and-stop points along a longer weld joint typically require a gun that can handle extended weld times.
The weld joint design and type or thickness of the material can also help determine whether to switch to a water-cooled MIG gun. For instance, heavy plate sections that have been preheated can generate substantial radiant heat that impacts how well a gun cools, and can adversely affect the life of the front-end consumables. In this scenario, a water-cooled gun would be better suited for the job.
When deciding whether a water-cooled robotic MIG gun is the best choice for an application, it’s important to keep in mind some maintenance and replacement costs. While a water-cooled gun costs more upfront, there is the possibility to conduct maintenance on each individual component within the cable assembly (e.g. water lines, gas hose, etc). However, an air-cooled cable combines all its components into one common part and if any single component fails, the entire cable needs to be replaced, resulting in higher replacement costs. It is necessary to weigh those factors against each other.
Understanding water-cooled robotic MIG guns
Welding guns — whether air or water-cooled — must stay cool to protect the power cable, gun body, neck and consumables from heat damage during welding. That heat takes three forms: radiant heat from the arc; resistive heat from the electrical components in the welding circuit; and reflective heat from the welded part, particularly aluminum or preheated parts.
Whereas an air-cooled MIG gun relies on the ambient air, shielding gas and arc-off time to dissipate heat, 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 then returns to the radiator, where the radiator’s baffling system releases the heat absorbed by the coolant. There are also guns available on the market today that cool only the front of the gun, where heat is generated, and still use an air-cooled cable.
Air-cooled MIG guns also use much thicker copper cables and inner neck tubes, whereas water-cooled robotic MIG guns use much less copper in the power cables and thinner wall sections in the necks because the coolant carries away the resistive heat before it builds. Water-cooled MIG guns, however, do have multiple inner lines that run through the neck to the front-end consumables, making this portion of the gun heavier than an air-cooled neck.
When to switch to a water-cooled robotic MIG gun
There are three key indicators that signify a welding operation could benefit from converting to a water-cooled MIG gun:
1. Excessive consumable usage
2. Excessive gun temperature (overheating)
3. Excessive cycle time (high duty cycle)
All these factors are interconnected, because if the weld is too hot, excessive consumable usage and gun temperature will automatically result.
In general, water-cooled robotic MIG guns are most beneficial for high-amperage applications and are typically available in 350 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 have varying duty cycle capacities depending on the manufacturer and model. It is important to make the appropriate comparison during the selection process, as some guns may be rated at either 60% or 100% duty cycle, which results in different amperage ratings.
Converting to a water-cooled robotic MIG gun
Fabricators who plan to change from an air-cooled to a water-cooled robotic MIG gun should follow these three steps to help ensure a smooth conversion.
Match the existing tool center point (TCP) and approach angle. Be sure to have access to all the weld joints with the new water-cooled MIG gun. Make sure that the tooling will work with the new system. The gun may require a special neck or special mounting arm to achieve the desired TCP. Often, converting to a water-cooled gun will require a new mounting arm and insulating disk to maintain or achieve a specific TCP while changing the dimensions of the neck itself to create better access.
Ensure overall clearance. A 3-D simulator can help determine whether all parts of the new system will clear all tooling or any other obstructions. In addition to having front-end clearance and access – once installed, it’s important that the gun body and cable bundle fits properly to avoid getting caught on tooling or other equipment.
Get a water cooler. It is necessary to invest in a radiator for the new water-cooled robotic MIG gun. Ensure that the water-cooler has been installed and maintained, as per the manufacturer’s specifications.
Maintenance and usage tips
Because all the lines and hoses in a water-cooled robotic MIG gun are separate, it is possible to conduct maintenance on individual components if they become damaged. However, due to the lines being internal to the gun, it is difficult to perform preventive maintenance on them. There are options though to care for a water-cooled gun.
As with an air-cooled MIG gun, 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). Ensure there is a flow switch installed in the return line from the gun and the radiator to indicate any leaks within the system — this component will save time and money in the event of a failure.
Using a 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 further extend consumable life. This feature adds to the overall cost of the equipment, but it helps increase uptime for production since there is less manual intervention. The ROI is typically worth it.
It is important to always use the correct coolant — do not fall prey to the notion that it is cheaper to use tap water in a water-cooled gun. Doing so can cause algae growth or mineral build-up and, eventually, lead to costly 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.
Lower operating costs
Although converting to a water-cooled robotic MIG gun is often more of a necessity than a choice (because the application demands it), this type of gun has its value. Applying a water-cooled gun to the appropriate application can result in a more efficient system performance and lower overall operating costs.
Consider the various costs, specific application needs and joint accessibility to determine whether a water-cooled robotic MIG gun is the best option for the specific robotic application — and don’t hesitate to consult a trusted welding distributor, welding equipment manufacturer or robotic welding system integrator with questions.