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.

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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:

• 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.

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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.

How do I choose a MIG gun?

Selecting a MIG gun should be done with just as much attention to detail as the welding power source itself. Think of it as the human body: an injured toe inhibits our ability to perform basic functions such as walking. The gun is just as critical to the quality of the weld itself and the productivity of your operators. There are also important considerations when selecting a MIG gun that may help you lower your operating costs. Let's take a look at common types of MIG guns and considerations for selecting the gun that&#;s right for you.

Choose wisely: Types and varieties of MIG guns

The choice of a MIG gun goes beyond just air- or water-cooled models. There are five basic MIG welding gun options; here's what you need to know about each:

Air Cooled: Air-cooled guns use ambient air and shielding gas to dissipate excess heat. The power cable on an air-cooled gun contains more copper to help prevent the cable insulation from melting or burning. As a result, air-cooled guns are heavier and less flexible compared to water-cooled guns in most cases. Air-cooled systems, however, are less expensive as they do not require an independent radiator cooling system and extra hoses that are associated with water-cooled systems. The simpler design of air-cooled setups makes them easier to operate, assemble, maintain and support. Air-cooled MIG welding guns are typically available in a wide range of amperages, between 150 and 600 amps.

Water Cooled: Water-cooled MIG gun systems require a radiator cooling system that circulates water, the ambient air and shielding gas to dissipate heat from the gun. However, water-cooled gun cables are lighter and more flexible because the cable contains less copper compared to air-cooled systems. Water-cooled MIG guns are typically available in 300- to 600-amp ranges.

Push-Pull: These guns are particularly helpful when welding soft alloys such as aluminum, small diameter stainless, silicon bronze and cored wires. They are available in both air- and water-cooled designs. Push-pull guns are an excellent option when welding far away from the power source &#; some push-pull guns are capable of working more than 50 feet away (although 15- to 35-foot distances are more common and preferred). This is not always ideal, but is helpful when accessibility is an issue. Push-pull systems feature a push motor at the feeder that works in conjunction with a pull motor on the gun, effectively allowing the wire to feed through the liner with minimal resistance. The feeder and the gun must be compatible for these systems to work. Push-pull guns are typically available in gooseneck and pistol-style grip to meet application demands and operator preference.

Spool Gun: Spool guns improve feeding of soft wires by locating a small spool of wire, typically about 1 pound and 4 inches in diameter, on a pistol-grip style gun. Because spool guns only need to feed the wire a few inches before it hits the weld puddle, they eliminate the potential problems created by pushing soft wires through a regular gun, such as birdnesting. This type of gun is particularly helpful with welding aluminum. A spool gun is best suited for occasional MIG welding at low amperages, such as MRO.

The key to a spool gun is flexibility. Duty cycles are typically lower, but spool guns offer a cost effective entry point into MIG welding. It can be used with any power source with a 14-pin connection, including some engine drives. So, you don&#;t need to buy new power sources to get into MIG welding aluminum in most cases.

Fume Extraction Gun: Fume extraction guns capture the fume right at the gun and connect back to a high-vacuum fume extraction system. Typically rated up to about 400 amps, these models have become more efficient and user friendly with features such as adjustable extraction control (so as not to disturb shielding gas flow while still providing excellent fume extraction), a smaller vacuum chamber (for ease-of-handling) and improved neck designs for better joint access.

These MIG welding guns provide extra defense against welding fumes, such as those encountered when welding certain varieties of stainless and galvanized steels, and when welding with wires and steels containing high levels manganese.

Flux-Cored Guns: While the same machine can typically be used to run both MIG and flux-cored wires, a MIG gun is not recommended to run the flux-cored process. Flux-Cored welding is typically hotter and rougher on front-end consumables. There are, however, consumable conversion packages that will allow you to run flux-cored wires on a standard MIG gun. Otherwise, if you plan to run the flux-cored process, invest in a dedicated flux-cored gun.

Top considerations for gun selection

1. Application: Whether you choose an air- or water-cooled MIG welding gun often comes down to operator preference. High-amperage pulsed MIG applications typically rely on water-cooled systems, as do applications that run larger diameter wires (1/16-in. and up). Applications with smaller diameter wires (.035-, 3/64-in.) tend to more often use air-cooled guns. Companies that run a helium mix tend to prefer water-cooled systems as helium runs hotter than other gas mixes. In general, water-cooled guns also help consumables last longer because the tip, nozzle and diffusers all run cooler. This creates less downtime and increases cost savings.
   
   Also, are you welding in the shop or in the field? Air-cooled MIG guns are more practical for outdoor use because they require fewer parts, simplifying transport, set-up and parts management. Water-cooled systems make more sense in stationary applications because of the required water-cooling system and hoses.
   
   As mentioned before, when welding with softer wires, push-pull and spool guns provide greater support to prevent feeding problems.
   
   
2. Amperage Ratings/Duty Cycle: One of the most common mistakes is to buy a gun with the wrong duty cycle. Guns rated at 600 amps will more than cover almost any application you can think of. However, the added size, weight and cost of a gun with that high of a rating may exceed your needs and fatigue the operator. A gun rated at 150 or 200 amps will cost less, be lighter and easier on the operator, but won&#;t be suitable for extensive welding on applications that may require 300-400 amps. As new work comes in that requires MIG welding at higher amperages, you may find yourself buying a higher-amperage gun anyway.
   
   It&#;s a delicate balance: you may weld at 400 amps, but a gun rated at 300 amps/100 percent duty cycle may work because you realistically will not be welding 100 percent of the time. The average &#;arc-on&#; time for a welding operator over an eight-hour day is roughly 30 minutes for each hour. Consider your welding application and determine, based on average amperage and arc on time, what MIG gun will be best.
   
   
3. Cost: Water-cooled systems offer a higher cost of implementation due to the added components (e.g. cooling system, hoses). This means there are more parts and components that may be prone to downtime. On the other hand, as previously stated, water-cooled systems help consumables last longer, helping reduce those associated costs.
   
   Push-pull guns are ideal for welding soft wires and will provide greater performance and productivity than using a push-only system. However, these need to be coupled with compatible wire feeders and systems, potentially increasing the cost of implementation. If you infrequently weld with these wires, a spool gun may prove to be a wise choice because it will work with most of the welding systems you already own (provided they have a 14-pin connection) and will not require you to buy new equipment in most cases
   
   
4. Components/Consumables: A welding system is only as strong as its weakest part. Here are a few things to look at when specifying a MIG gun:

a. The back end: A heavy, sturdy power pin designed to seal the connection tightly helps prevent problems such as electrical resistance, overheating, gas leakage and poor conductivity. Look for a rigid strain relief at the connection between the power cable and the wire feeder. This will prevent kinking and improve feeding. Also, select a MIG welding gun with multiple, interchangeable plug options. A gun that can be matched with multiple feeders allows you to standardize on one type of gun and consumable. This helps to reduce equipment costs, minimize inventory and simplify the entire process.

b. The liner: There are three key factors when looking at liners: make sure there is a good gas seal and/or solid o-ring connection at the back of the liner to prevent gas leaks; choose liners with durable jacketing or coating to prevent additional gas loss, and select a liner designed for your diameter wire. Also, look for a liner that is easy to remove and replace to minimize downtime. Push-pull guns use unique liners designed specifically for this type gun, usually made of teflon or a type of plastic.

c. The power cable: A cable that is too light for your application can cause the gun to overheat and may lead to poor welding performance. On the other hand, a cable that is too large can be cumbersome and cause clutter on the shop floor. A good rule of thumb is to use the smallest and shortest cable possible without limiting your welding needs. Smaller cables reduce operator fatigue, minimize clutter and help prevent excessive coiling that can lead to poor wire feeding.

d. Trigger options: Triggers are the only moving part on a MIG welding gun that can fail due to mechanical motion. Look for a strong, reliable trigger that is easily serviceable to help minimize downtime for component changeovers. Also, choose a gun that gives you the most appropriate trigger option for your application: standard, locking, dual pull and dual schedule switches are all available through most manufacturers. These options allow your welding operators to work with the trigger set-up that best suits them and the application. It will also further increase productivity by making welding more comfortable.

e. Neck and handle options: MIG welding guns are available with fixed, rotatable and flexible necks of different lengths and angles to provide flexibility when welding in various positions or tight quarters. Rotatable necks allow you to weld out-of position more comfortably without changing your gun handle or sacrificing quality. Operators can easily adjust flexible necks to fit different positions, and they save time and money for changing out and/or inventorying expensive specialty guns for a given application. Also, choose a neck with good armor (hard plastic or metal) to protect it from damage that could lead to shorts and failures in the gun. When looking at handle options, consider lightweight, comfortable styles that will meet your amperage/duty cycle rating needs. Similar to the power cable, a smaller gun handle makes it easier for you to weld. Also, a ventilated handle can reduce heat and increase your comfort and productivity.

f. Consumables (nozzles and tips): Less expensive consumables do not always translate into cost savings. Ultimately, you get what you pay for. By selecting a consumable based on longevity instead of price, you can reduce costs for replacement parts and for changeover time. You will likely spend more money upfront for such consumables, but more durable consumables can help reduce overall operating costs in the long run by increasing productivity and reducing downtime. It is also important to look for heavy duty tips and nozzles that provide good conductivity and gas coverage to help ensure good arc starts, less spatter and less rework and clean-up.

As you can see, the choice is much more complicated than simply picking the least expensive or most powerful gun that matches your machine. Careful consideration of your welding process, operator preferences and performance/comfort will lead you to the right MIG welding gun.

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