5 things to know about robotic GMAW guns

When choosing the best robotic welding system for your operation, make sure to pay special attention to the

When choosing the best robotic welding system for your operation, make sure to pay special attention to the gun and consumables. One size does not fit all.

While the robot itself, proper programming, and oversight by a trained supervisor are all important components in the overall robotic welding operation, the robotic GMAW gun also has a direct impact on quality and productivity, as well as costs.

When it comes to robotic welding, precision, repeatability, and speed are essential to ensuring a successful outcome. Companies rely on the robot’s ability to execute the same weld, exactly the same way, and as fast as possible.

While having the robot properly programmed and monitored by a trained welding supervisor is important, the gun used also has a direct impact on quality, productivity, and costs.

Consider some of the top things to know about robotic gas metal arc welding (GMAW) guns as a way to get the most out of this equipment.

1. One size does not fit all when it comes to robotic GMAW guns.
As with any piece of welding equipment, the right robotic GMAW gun for the job depends on the application— specifically, on the material being welded, the thickness, amperage, and required arc-on time.

Air-cooled guns provide the best results for low-amperage applications on thin materials (up to 0.16 inch thick) and for applications with short welds in high volume, such as those in the automotive industry.

These guns rely on the ambient air, as well as the copper in the unicable, to cool them during the welding process and typically are quite durable. In the event of a collision, the stronger neck construction helps reduce the opportunity for bends compared to a water-cooled model. Air-cooled guns generally are available in a range of 300 to 500 amps.

Water-cooled robotic GMAW guns are better suited to applications that require high- amperage welding for longer periods of time, particularly on materials over ¼ inch thick and on longer weldments.

Models often range from 300 to 600 amps at up to 100 percent duty cycle. These guns require an external cooler and, therefore, cost more upfront and require more maintenance. To prevent overheating on high-amperage applications, however, the additional cost and upkeep may be worthwhile.

For companies welding materials of varying thicknesses requiring both high and low amperages, a hybrid air-cooled/water-cooled gun is a viable option. These guns have a durable neck like an air-cooled gun with exterior water lines to cool the front-end consumables, making them easier to maintain. Should the gun have a water-line leak, it can still operate for a time (via the cooling capacity of the air-cooled unicable), so operators can address the problem before a complete failure occurs.

2. Added features benefit performance.
Manufacturers build robotic GMAW guns with precision in mind. The goal is to complement the robot with features in the gun that help the entire system maintain its repeatability, quality, and speed. Adding options like an air blast or wire brake to the gun can help.

An air blast feature blows high-pressure air through the front of the gun (air-cooled only), helping to remove debris. The goal is to remove any contaminants that could enter the weld pool and potentially cause poor weld quality. By reducing that risk, the air blast feature also helps reduce the need for rework. It supports more arc-on time, as it can be programmed to operate between weld cycles.

Another optional feature that can add to the consistency of a robotic GMAW gun is a wire brake. This feature stops the wire from feeding through the gun when the welding stops, allowing for uniform stick-out (or extension) at the start of the next weld.

For robots that use touch-sensing software, a wire brake is invaluable; it holds the welding wire in a set position while the robot moves and searches for the weld joint, helping to ensure that the robot can accurately determine the location of the weld joint and create a consistent, high-quality weld. A wire brake also helps prevent unspooling inside the gun during each stop and start.

3. The right neck and cables can help streamline the process.
Gaining access to the weld joint is critical for a robot to execute an accurate weld time and time again. In many cases, companies are moving to smaller robots and smaller weld cells to maximize floor space so they can produce more parts and become more competitive. These changes make it increasingly necessary for the gun to have a neck design that allows it to maneuver into the weld joint unhindered. Many gun suppliers offer various neck lengths and angles (with or without requiring special orders), and some offer online configurators that customize a gun for the exact application.

Sturdy cables that are easy to change out help to create a more efficient operation. Look for cables constructed of durable materials to protect against UV damage from the arc or general wear from air movements. Features like rotating power connections also can help by minimizing stress from routine torsion.

4. Guns operate more efficiently with the right consumables.
The right consumables—nozzles, contact tips, gas diffusers (or retaining heads), and liners—are essential for achieving maximum performance and reducing downtime. Gun manufacturers offer consumables for a range of applications, including heavy-duty products, such as chrome zirconium contact tips for high-amperage robotic welding. These tips are harder and more durable than copper tips, so they tend to last longer.

Contact tips that help improve arc starting also are available.

The liner used with the robotic GMAW gun can have an impact on the overall efficiency of the operation and gun performance. It is important to cut the liner to the correct length. A liner that is too short can lead to poor wire feeding and birdnesting (a tangle of wire in the wire feeder drive rolls). A liner that is too long can cause kinking, wire feeding issues, and shortened contact tip life, all factors that can interrupt production. Always follow the manufacturer’s recommendation for trimming the liner. Use a liner gauge as a guide when possible.

The type of liner used also plays a part in keeping the system up and running more effectively. Front-loading liners help reduce downtime by allowing the gun to stay connected to the wire feeder while the operator completes the changeover from a safe zone in the robotic weld cell.

Spring-loaded modules work in conjunction with a front-loading liner to help minimize problems if a welding operator cuts the liner to an incorrect length. These modules are housed in the power pin and put forward pressure on the liner after the welding operator installs it from the front of the gun. They allow up to 1 in. of forgiveness if the liner is too short. Again, these types of liners can help reduce time for addressing wire feeding issues that could affect productivity.

5. Preventive maintenance is not optional.
Companies invest in robotic welding systems in part to seek out productivity gains in their operation. With that in mind, the goal is to keep the system running as much as possible, but scheduling downtime for gun maintenance is essential.

The scope of a preventive maintenance (PM) schedule for a gun varies according to the application, but all companies should have a general maintenance sheet that indicates how often components on the gun should be and are changed. Tracking the maintenance activities makes it easier to troubleshoot a problem should it occur; maintenance personnel can look at the last thing changed during gun PM to see if that variable is a factor in the issue.

Routinely look for secure, clean connections between the neck, the diffuser, and the contact tip. It’s important to check that the nozzle is secure and that any seals around it are in good condition. Such activities can take place during routine pauses in welding, while other, more intensive maintenance can occur offline.

An effective PM program should include an appropriate parts inventory for the gun, including consumables. If something fails or needs to be replaced during PM but is not available, it can cause significant downtime in the production.

Other items to consider.
Be sure to select a gun with the right amperage to accommodate the application at hand. If you are using a conventional robot (as opposed to a through-arm style), selecting the right cable length for the gun also is important to prevent unnecessary wear.

Training employees on the proper operation and maintenance of the gun is critical. While GMAW guns are a seemingly small part of the overall robotic welding system, when they are selected, installed, and managed properly, they can contribute positively to the overall efficiency of a robotic welding system.

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