From semiautomatic to automatic: Tips for selecting a welding gun

Choosing the right equipment for a welding operation is critical to achieving high weld quality and productivity while also eliminating costly downtime. And that includes welding guns. Image provided by Tregakiss

Choosing the right equipment for a welding operation is critical to achieving high weld quality and productivity while also eliminating costly downtime. And that includes welding guns.

In many cases, fabricators have a mix of welding processes and guns. For example, in heavy equipment and general manufacturing, it’s common to perform semiautomatic welding along with robotic welding. In oil and gas and shipbuilding applications, semiautomatic welding and fixed automation are prevalent. The combination of welding processes and equipment allows companies serving these industries to weld a variety of part volumes and sizes.

These process mixes, however, can pose challenges in terms of gun selection. That’s why it’s important to know the best welding gun features to look for to achieve the desired weld results — and the best efficiencies.

Duty Cycle and Amperage

One of the most important factors for all guns — semiautomatic, robotic, and fixed automatic — is to select the correct duty cycle. Duty cycle is the amount of time in a 10-minute period that a gun can operate without becoming too warm. In the case of a semiautomatic welding gun, it’s the point at which the welding handle becomes uncomfortably hot.

Manufacturers rate their guns differently. For selecting any type of gun, it’s important that the desired duty cycle is what will actually be delivered. Guns are rated at 60% and 100% duty cycle. If an operation needs to have a lot of arc-on time, then choosing a gun with a 100% duty cycle may be a good option. It will allow welding for the full 10 minutes without becoming too warm or potentially overheating, which would lead to a gun failure.

Using a gun with the correct amperage is also critical and should be matched to the requirements of the application. Semiautomatic guns are available in ranges from 200 to 600 amps. Robotic and fixed automatic guns vary in amperage according to the manufacturer and whether they are air- or water-cooled. The average range is between 350 and 600 amps.

Semiautomatic Welding Guns

A semiautomatic gas metal arc welding (GMAW) gun is a welding operator’s primary piece of equipment, used daily and often for many hours. For that reason, it is important that the gun is comfortable as well as capable of meeting the requirements of the job.

The type of handle contributes directly to welding operator comfort. Some gun manufacturers provide the option to customize their product, allowing a welding operator to select the style he or she prefers. Straight and curved handles are common options. Ventilated handles are also available to reduce heat.

Look for welding guns that have mechanical compression fittings, as they tend to be more durable and can be repaired if damaged. Guns with crimped fittings cannot be repaired.

Other gun features to consider during the selection process are:

A semiautomatic gas metal arc welding (GMAW) gun is a welding operator’s primary piece of equipment, used daily and often for many hours. For that reason, it is important that the gun is comfortable as well as capable of meeting the requirements of the job. Image provided by Tregakiss

• Power cables: Select the shortest one possible to prevent kinking that could lead to wire feeding issues. Shorter cables also tend to be lighter and more comfortable for the welding operator and are good choices if space is limited within the weld cell or fixturing to work around.
• Triggers: Several styles are available, including standard, locking, dual-pull and dual-schedule switches. Consult a GMAW gun manufacturer or trusted distributor to make the best selection.
• Gun neck: Flexible and rotatable options are available to improve comfort and offer access to hard-to-reach weld joints. Those with less bend tend to reduce the opportunity for wire feeding issues.

It may take some trial and error for a welding operator to find the right gun features for the job and a gun that is most preferred. Communicating with team members or management can help.

Robotic Welding Guns

Robotic welding guns are available in conventional and through-arm styles in a variety of amperages, with the latter being most popular today. Through-arm robotic welding guns, as the name implies, run the power cable through the arm of the robot as opposed to over the arm like a conventional gun. This feature helps reduce cable wear caused by the cable being restrained within the robot casting, which eliminates the need for additional cable management devices.

When selecting a through-arm welding gun, the key is to have the correct cable length to avoid twisting or kinking, which occurs with a too long cable. If a cable is too short, it can stretch and lead to premature failure. Manufacturers typically offer through-arm guns with a set cable length that can be matched to the specific robot model. However, if the feeder mounting bracket is customized or the feeder is placed in a nonstandard position, the gun length requirement can change on through-arm cables.

Neck length and angle are additional features factoring into the selection of a robotic welding gun. Manufacturers generally offer necks in short, medium, and long lengths in angles from 180 to 45 degrees. Special-order options are also available to meet custom tool center point (TCP) requirements.

It is important to consider mounting options to protect the gun and optional technologies that can enhance its performance.

• Clutch: This electronic peripheral attaches to the robot to protect it and the gun from damage should a collision with tooling or a part occur. It stops the robot so any damage can be assessed and TCP can be verified before production resumes. A clutch is used with robots that do not have collision detection software.
• Solid mount: This is an alternative to a clutch for holding the robotic GMAW gun in place on robots with collision detection software.
• Air blast: This optional feature blows compressed air through the front end of the robotic welding gun to clear it of debris. It helps reduce the risk of contamination in the weld and supports high weld quality.

If a company is implementing robotic welding for the first time, it’s imperative that the choice of robotic welding gun is part of the planning process. CAD models for simulation help to ensure the gun will fit the work envelope, be able to access the weld joint, and maneuver around fixtures.

Fixed Automatic Welding Guns

Unlike robotic welding guns that attach to the arm of a robot which moves around a stationary part, fixed automatic welding guns stay in one place while the part moves. For example, a pipe may be rolled while the gun welds the joint. Or the guns can be mounted in a holder and moved along a linear weld joint by way of a seamer.

The length of the neck is key on a fixed automatic gun. It must be long enough to fully reach the part and access the weld joint correctly. Most guns require a neck between 12 and 16 in., but there are exceptions that may require customization. Multiple neck angles are available in the marketplace as well. The most common angle is 180 degrees, but necks are also available with 22-, 45-, and 60-degree bends.

Cable length is important too. The distance from the wire feeder can vary from the part being welded. It’s common to have the feeder on a boom, which may require a cable as long as 15 ft. In other situations, the feeder may be mounted right on the tooling. In this case, cableless automatic fixed guns are available that comprise the gun, the neck, and a power pin that connects directly to the wire feeder.

Other Thoughts

In addition to selecting the right features for semiautomatic, robotic, and fixed automatic welding guns, there is value in considering the consumables. In particular, consumable systems that can be used with each of these types of guns can help streamline inventory and prevent mistakes during installation. If a single contact tip style and size is used, for example, the risk of operator error during changeover is eliminated. This, combined with having the right features on the welding gun, can go far in helping minimize downtime and gaining efficiencies throughout the welding operation.

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