Selecting the Right GMAW Gun for the Job

Many may be curious, “how much of a difference does your welding gun selection make?” If you are engaged in gas metal arc welding (GMA), it is crucial to pick the right tool for your unique needs.

Selecting a welding gun requires careful balancing of initial costs, operating costs and maintenance requirements, operating preferences and application needs. The right selection will depend primarily on the type and volume of welding you do and the materials you weld on. The wrong welding gun can have a negative impact on operator comfort and safety, productivity, equipment life, weld joint quality and your bottom line. This article will discuss some considerations in choosing the right gun for your shop.

Air or Water Cooled?

When it comes to selecting a gun for GMAW, the first decision to make is whether you want it to be air or water cooled. Welding guns must have a cooling system to prevent the gun itself from overheating. Without some form of cooling, excess heat can make the gun too hot to handle or damage the materials in the contact tip, gun head or electrical system.

Air-cooled—sometimes called gas-cooled— guns rely on the shielding gas to dissipate heat into the ambient air. Conversely, water-cooled guns have a extra hose inside that carries a coolant pumped from a radiator. Similar to that of a car radiator or air conditioning unit, this coolant cycles through the weld gun, carrying excess heat to the radiator unit where it is dissipated using a baffle system.

Pros and Cons of Air- and Water-Cooled Welding Guns

While both air- and water-cooled guns can be utilized for the same types of welding applications, the systems have different strengths and weaknesses.

Air Cooled Pros

  • Lower coat
  • High portability
  • Low maintenance requirements

Air Cooled Cons

  • Lower cooling efficiency
  • Greater weight for the same amperage
  • Greater risk of overheating with long operating cycles
  • Lower maneuverability
  • Increased operator fatigue
  • Decreased operator comfort

Water Cooled Pros

  • Better cooling efficiency
  • Reduced weight for the same amperage
  • Greater maneuverability
  • Reduced operator fatigue
  • Increased operator comfort

Water Cooled Cons

  • Higher initial cost
  • Higher system operating costs
  • Higher maintenance requirements (e.g., monitoring and replacement of cooling fluids)
  • Low portability
  • Risk of water-related equipment damage or safety hazards if not properly maintained

What Air- and Water-Cooled Welding Guns are Best For

Air Cooled

  • Low-amperage applications
  • Shorter duty cycles

Water Cooled

  • High-amperage applications (e.g., aluminum)
  • Longer duty cycles

Generally, here’s what you can expect from the different types:

  • Air-cooled guns are more portable than water-cooled systems and less expensive to buy and operate. They are also heavier than water-cooled guns with the same amperage rating; need a longer swan neck to allow heat from welding to dissipate before it reaches the handle and thicker copper cabling to reduce heat from electrical resistance; and are available with ratings from 150 to 600 A.
  • Water-cooled guns have greater cooling efficiency. That means the actual gun can be smaller and lighter for the same amperage, reducing operating fatigue. However, these systems are more expensive and require more maintenance as well as the purchase of coolant solutions. Water-cooled systems are available with ratings from 300 to 600 A.

Other Factors to Consider When Choosing Welding Guns

Water cooled vs. air cooled is not the only decision that needs to be made. Within each of these categories, there is wide variation in gun design and capabilities.

The right welding gun well depend on your amperage requirements, the amount of time the gun will be on, the materials you are welding and additional considerations such as mobility needs and ergonomics. The factors to consider when selecting a welding gun for you application include:

Amperage

Amperage needs are significantly driven by the type of material you are welding. Thicker materials require more amperage than thinner materials, and different metals have different optimal amperage recommendations. The higher the amperage, and the longer the time the gun will be on, the more benefit you will gain from a water-cooled system. No matter whether you choose air or water cooled, be sure your gun is rated for the highest amperage you expect to use in your shop.

Application

In addition to the design of the gun itself, operators also need to make the right selections for replaceable/interchangeable components such as liners and contact tips. The material you are welding and the type and diameter of wire you are using will determine these selections. For instance, normal copper contact tips can be utilized to weld normal steel. However, you will need a harder tip, typically an alloy such as copper chromium zirconium (CuCrZr), for stainless steel welding. For aluminum, a standard copper tip is fine, but you will want a larger hole to accommodate the softer wire. Additionally, the wires must be matched to the application. A Teflon™ liner is required for aluminum and stainless steel welding, while a steel liner will work for standard steel applications.

Swan Neck Design

Weld guns come in a variety of swan neck lengths and curvatures. The right design will depend on your application as well as personal preference. A longer swan neck adds weight, but it puts more distance between the operator and heat generated by welding, and helps to dissipate heat before it reaches the handle. Curved necks are generally more comfortable to use for manual welding applications.

Ergonomics

How comfortable is the gun in your hand? How heavy is it? Is it easy to handle and maneuver? The more time you will spend holding the welding gun, the more important these ergonomic factors should be in your selection. A lighter, more comfortable gun reduces operator fatigue and increases productivity time. If you are only welding occasionally for short periods of time, you may be able to compromise on ergonomics to save overall cost.

Fume Capture

If you are engaged in high-production manual welding, you may want to consider a fume gun. With fume guns, both welding gun and fume extraction are combined in a single package, so weld fumes are captured right at the source as they are generated. New generations of fume guns such as the Extractor™ from Translas, The Netherlands, are much smaller, lighter and not much larger than a stand-alone welding gun. This newer fume gun can capture up to 90-95 percent of weld fumes at the source without reducing ergonomics for the operator. For ideal results, pair the fume gun with a quality high-vacuum dust collector such as the RoboVent FlexPro®.

Overall Quality

How well is the gun built? Are the components and connections well made and durable? After amperage rating and application suitability, quality should be the number one consideration in choosing a welding gun. This is particularly important if you are anticipating heavy use; a higher-quality product will save money over time through longer life and reduced downtime.

Troubleshooting: When the Gun Isn’t Up to the Job

If you don’t have the right gun for your application, you will soon find out through poor weld joint quality or reduced gun life. Here are a few of the common mistakes to look out for.

Failing to Change the Liner for the Application

Utilizing the wrong liner has a negative impact on wire transport and will lead to uneven arcing at the weld tip. For example, when changing from steel to aluminum, it is crucial to change to a Teflon™ liner to ensure a smooth, continuous wire feed.

Dirty Liners

Even if you have the right liner for the material you are welding, it will eventually wear down and get dirty. As wire goes through the liner, small particles are worn off. Over time, these particles will clog the liner and result in issues with wire transport. Liners should be cleaned weekly with compressed air and replaced regularly to avoid problems.

Old Contact Tips

As contact tips age, friction and wear cause the hole to increase in diameter. Eventually, this will cause excessive motion of the wire as it comes out of the contact tip, resulting in instability in the arc length and poor weld joint quality.

Overheating

Using a higher amperage than the gun is rated for, using the gun for excessively long duty cycles or allowing coolant to run out in a water-cooled system can result in overheating. Regardless of the cause, overheating is dangerous for the operator and bad for the gun. Overheating the contact tip will result in the metal expanding, which reduces the size of the hole. This can cause problems with wire transport. The wire will no longer feed smoothly from the tip, leading to uneven arcing, potentially causing the tip to burn along with the wire.

Inadequate Shielding Gas

The shielding gas protects the weld joint and helps to cool the gun. When the amount of the shielding gas is inadequate, the resulting weld joint is highly porous, and may display visible pits and craters. It is important to check not just the amount of gas left in the tank, but also the amount that is actually coming from the gun to ensure adequate shielding gas.

 

Selecting the right weld gun for job, as well as the right components and consumables, will go a long way way toward increasing the life of your weld gun, maintaining weld joint quality and improving operator comfort and safety.

Source: aws.org

Leave a Reply

Your email address will not be published. Required fields are marked *