Welding Gun Selection

Step One: Accounting for the amperage and duty cycle

When selecting a welding gun, first consider the type of material that will be welded, as well as its thickness. These factors will reveal the amperage necessary to perform the proper weld. Choose a gun with an amperage rating that matches the needs of the application and aligns with the capability of the power source that will be used. There’s no reason to select a gun above the amperage needed to weld – if the amperage is too high, a welder likely will end up with a gun that is too heavy, leading to unnecessary operator fatigue, or one that is too bulky for the workspace, complicating the task at hand. For instance, don’t select a 500 amp gun if only 350 amps are needed for the application.

Once amperage is determined, a welder can establish the gun’s necessary duty cycle, or how long it can run continuously in a 10 minute cycle. If the gun will be used in semi-automatic applications, 60 percent duty cycle is most common and should suffice; however, for robotic welding, some manufacturers offer guns rated up to 100 percent duty cycle, as there is no need to account for operator fatigue or time to rest.

Another factor relating to the rated duty cycle of the gun is the type of shielding gas used. As indicated, many semiautomatic guns are commonly rated at 60 percent duty cycle when used with CO2 shielding gas. Some high capacity designs are rated at 100 percent duty cycle with CO2 gas.  However, as mixed gases containing Argon are introduced to the application, the same guns’ amperage rating is decreased at a given duty cycle.

Also, more common in automated applications, the question of air-cooled vs. water-cooled guns or torches must be addressed. In short, water-cooled torches have the capacity to run cooler and be lighter in weight, but the cost can be more than double that of an equivalent air-cooled gun with the same duty cycle.

Selecting a high amperage gun when unnecessary may result in gun with too much unnecessary bulk or weight.

Water-cooled robotic torches can double the cost of an equivalent air-cooled torch with the same duty cycle.

Lincoln Electric’s Anti-Seize™ thread design for contact tips and diffusers help to dissipate heat and extend service life.

Copper Plus® design contact tips add more mass to withstand more heat.

Select a gun with a full group of consumables, including various nozzles, like this extended version for tight spaces.

Step Two: Examining the expendable parts options

After considering amperage and duty cycle, examine a gun’s expendable parts. These components will degrade over time due to heat, spatter and wear during normal welding operations, so their lifespan affects the cost of gun ownership over time. Parts that last longer tend to keep costs down.
 
When battling elements like heat and wear, attention to detail in design can make all the difference. First, you might start by closely examining the thread design of the contact tips and diffusers. For best performance, select guns with Anti-Seize™ tips and diffusers, like those in the Magnum® PRO line from Lincoln Electric. Anti-Seize tips have threads with a flattened profile, increasing the cross-section where heat typically concentrates and tips tend to fail. This technology leads to reduced melting, fusion and seizing and extends contact tip service life. This characteristic helps to reduce both expendable part and labor costs, while increasing a welder’s time with a usable arc.

Next, consider the mass of the expendable parts. Remember, within reason, the larger the contact tip, the more heat it can withstand over long periods of time, giving it better heat deflection and longer life. Try to choose contact tips from a manufacturer that offers contact tips with a larger mass; for instance, Lincoln Electric provides contact tips that contain up to 40 percent more mass than other welding equipment suppliers.

Third, think about the type of alloy used in the contact tip, as it affects both the heat resistance and wear resistance. For example, when welding wire is fed through the tip, the hole can become elongated or misshapen over time if the material doesn’t withstand heat or wear well, resulting in improper electrical contact and welding issues caused by a wandering arc, discontinuities caused by dropouts and other issues. While many contact tips are made from various types of copper, some manufacturers have begun to market designs containing harder materials. These harder materials can withstand greater heat, last longer and resist elongation or wear at the contact tip.

Welders should also consider their application when selecting the proper nozzle. There are many different nozzle types, shapes and sizes and choosing the best match for the application can make a big difference in performance. For instance, if welding in a tight space, use a nozzle that is longer and more tapered, as the conical shape allows for easier accessibility into tight joints. In addition, some manufacturers, like Lincoln Electric, offer expendables that position the contact tips slightly outside of the nozzle to allow even greater access to tight areas.

Think about the rating of the expendable parts, as well. Those with higher amperage are larger in size and mass, meaning they withstand more heat and have a longer life, but their size may make them difficult to use in tight spaces. Again, don’t choose a higher amperage rating than is necessary for your expendable parts.

Flexibility of the expendable parts is also key – many gun manufacturers have different front end expendable parts for each gun model or group, requiring a greater amount of inventory and organization on the part of the welder. For ease of use, it’s best to select a gun manufacturer that provides fewer sets of expendable parts that can be used across all gun models, as is the case with the Lincoln Electric Magnum® PRO line. This single-source approach makes it simpler to manage shop inventory – there are fewer contact tip, nozzle and diffuser parts to track, understand, stock and order – and handling fewer parts also helps prevent operator error, as using the wrong expendable parts for a gun could result in poorer welding results, increased costs and potential rework. Finally, while many companies focus on the cost of the actual gun when making a purchase, it’s also critical to consider the cost of the gun’s front end expendable or consumable parts, as they comprise the bulk of the gun cost on an annual basis. Since most manufacturers have variability within the product range, select a manufacturer that provides expendables with long life and compatibility with all gun models for the greatest cost savings.

Because operators use and hold their guns in their hands all day long, it’s important for welders to consider their own comfort levels and preferences when selecting a welding gun, as these factors can affect weld quality and efficiency.
 
For instance, some welders may prefer a curved, more ergonomic handle that aligns with the shape of the operator’s hand. Sometimes, these handles are lighter weight, reducing instances of fatigue.
 
On the other hand, some fabricators may prefer a barrel, or broomstick style, handle. This shape offers more grip positions and has a smaller diameter that some users find more comfortable than a curved style.

Operators should also consider which type of expendable parts they prefer: thread-on, in which nozzles are screwed into the gun, or slip-on, in which the expendable parts are pressed on and held in place with the help of an O-ring.

Consider operator preferences for handle type and gun weight.

Maintaining a welding gun also affects the cost of ownership. Because guns are so integral to the welding process, they undergo significant wear and tear. Choosing a gun family with a simplified design is a sure way to make maintenance easy. For instance, choose guns that have a similar internal design, like those in Lincoln Electric’s Magnum® PRO line. This homogeneous design makes it easy for maintenance professionals to repair and service multiple guns without having to familiarize themselves with different internal works regarding trigger leads, connection points, and other features of the design.

And, not only are guns fighting heat, they’re also fighting operator abuse, leading to maintenance needs. To make maintenance simple, select guns that are designed to hold up to both heat and impacts.

When choosing a welding gun it is important to do your research. In order to obtain all of the elements necessary to weld, and ensure that they work well together, you typically have to select one manufacturer. Make sure you study your choices and select a welding manufacturer that offers high quality products and a wide array of options to meet your application, performance and operator preference needs.

One homogeneous internal design across gun models makes it easier for shop maintenance and repair teams.