What is GMAW welding, and how does it work?

‍

GMAW (Gas Metal Arc Welding) has been used to complete thousands of welds in automotive plants and metal fabrication shops. This welding method is one of the fastest ways to join metal parts while maintaining consistent, high-quality results. Here’s how it works and compares to other welding processes.

What is GMAW welding?

Gas Metal Arc Welding (GMAW) is a welding process that joins metals using an electric arc between a continuous consumable wire electrode and a shielding gas.

The arc is a super-hot discharge of electricity that jumps through the air between two conductors. In this case, between the wire electrode and the metal workpiece. This welding process gets its name from the gas that protects the weld.

During welding, a wire electrode continuously feeds through a welding gun while a gas (usually argon, CO2, or a mix) flows out around it.

When the wire touches the metal, it creates an electric arc that creates a plasma that can reach temperatures above 6,000°F (3,300°C). This is hot enough to melt both the electrode wire and the surface of the base metal.

As the wire continuously feeds into this molten pool, it fuses with the base metal. Then, once it cools, it solidifies into a strong joint.

The gas plays a key role here. It surrounds the arc and molten pool from the air, which would contaminate the weld and make it brittle.

Key equipment of GMAW welding systems

A GMAW welding system integrates several components to generate and maintain the welding arc. The power source supplies electricity, the wire feeder delivers filler metal, the gas shields the weld zone, and the ground clamp completes the electrical circuit.

Each component serves a specific function:

Step-by-step GMAW welding process

Proper setup and parameter selection determine weld quality and joint integrity. The process follows a systematic sequence:

Step 1: Select electrode wire

Pick a wire that matches your base metal and your welding requirements. The wire is continuously fed through the welding gun during the process.

Step 2: Attach ground clamp

Attach the grounding clamp to the workpiece to complete the circuit. Make sure it's firmly connected to bare metal.

Step 3: Adjust gas flow

Adjust the flow rate of the shielding gas to protect the weld pool from contamination. The flow rate depends on factors like wire size and amperage. Typically, a flow rate of 20 to 50 cubic feet per hour is used.

Step 4: Set welding parameters

Set the voltage, wire feed speed, and travel speed on the wire feeder or welding machine. These settings vary with the type and thickness of metal. It may take some testing to dial in the optimal settings.

Step 5: Position the gun

Hold the welding gun at a 10- to 15-degree angle and position the wire tip about 1/2 inch from the workpiece. Tilt the gun according to the direction that you’re welding in.

Step 6: Start welding

Squeeze the trigger to start the arc and begin moving the gun slowly and steadily along the joint. Move the gun at an even speed in a smooth, straight line, or small circles. Let go of the trigger to stop welding.

Step 7: Inspect & reinforce

Check that the weld penetrates fully into the joint and is slightly convex. Make additional passes as needed until the joint is filled to the desired reinforcement.

Types of GMAW welding

GMAW welding has different transfer modes, which describe how the molten metal from the wire electrode moves into the weld pool. 

1. Short-circuit transfer

The wire actually touches the weld pool. Each time it touches, the tip melts, transfers metals, and repeats many types per second.

Pros: Works well on thin metals, produces less heat and spatter, and can weld in all positions

Cons: Limited penetration, not ideal for thick materials

Typical use: Auto repair, light fabrication, thin sheet metal

2. Globular transfer

The wire melts into large droplets that fall into the weld pool under gravity. The transfer is irregular, which causes more spatter and less control.

Pros: Higher deposition rate (how fast you’re adding metal into the weld joint) than short-circuit

Cons: Messy arc, so it’s not suitable for out-of-position welding

Typical use: Thicker metals in flat or horizontal positions

3. Spray transfer

The wire melts into fine droplets that are sprayed steadily into the weld pool. It requires higher voltage and current and works best with argon-rich gas.

Pros: Smooth and stable arc

Cons: Generates a lot of heat, so it’s best for thicker metals and flat positions only

Typical use: Structural steel, heavy equipment, and large fabrications

4. Pulsed spray transfer

The current alternates between high (peak) and low (background) levels. During the peak, a droplet transfers; during the low, the pool cools slightly.

Pros: Combines the smoothness of spray transfer with better control and less heat

Cons: Requires a bit more setup

Typical use: Stainless steel, aluminum, and thinner materials where control matters

Applications of GMAW 

GMAW is one of the most common welding methods because it’s fast and works on many types of metals. The process supports production across multiple industrial sectors.

• Automotive manufacturing: GMAW is common in car factories because it quickly joins thin steel parts like doors, frames, and exhaust systems with strong, clean welds.
• Aerospace production: Aircraft and spacecraft builders use GMAW for aluminum and steel components that need precise, high-quality welds.
• Shipbuilding: Shipyards rely on GMAW to join large steel plates for hulls and decks. It works well for long welds and can be used in almost any position.
• General metal fabrication: Workshops and factories use GMAW for everyday metal projects from building machines to repairing tools because it’s fast, versatile, and easy to control.

Advantages of GMAW welding

GMAW welding delivers measurable productivity gains over alternative welding processes, including speed, reduced warping, and increased safety.

• Speed: Because GMAW uses a continuously fed wire instead of individual rods, you can weld much faster than with older methods like stick welding. You do more work in less time.
  ‍
• Less shape distortion: The arc in GMAW is small and easy to control, so it doesn’t transfer as much heat into the metal.
  
  Less heat means the metal is less likely to warp or bend. This also gives you better control of the molten weld pool for cleaner and more precise welds.

• Safer and easier to learn: GMAW doesn’t create a layer of slag that you need to chip away afterward. But as it uses gas, you need proper ventilation.
  
  It’s also a semi-automatic process, which makes it easier to learn. It’s also much safer if a welding cobot does it.

• Versatile and portable: The GMAW process can weld a wide range of materials like steel, aluminum, and stainless steel. It can work in all positions, including flat, horizontal, vertical, and overhead. 
  
  Plus, the equipment is lightweight, portable, and suitable for fieldwork.

Challenges and limitations of GMAW welding

GMAW delivers speed and flexibility, but the process has specific operational requirements and constraints:

• Equipment and gas requirements: GMAW requires a power source, a wire feeder, a welding gun, and shielding gas. That setup can get expensive, especially for industrial units. Moreover, you have to buy, store, and handle gas cylinders safely.
• Skilled operators: Even though GMAW is easier to learn than some methods, it still takes skill to set up and run correctly. Incorrect settings or poor technique can cause weak welds, porosity, or cracks. Welders need training and regular refreshers to stay up to date with new techniques.
• Porosity and cracking: If the gas flow or speed isn’t correct, you can end up with holes or cracks in the weld. Contaminants like oil, rust, or moisture make this worse. Careful prep and parameter control are key to avoiding defects.
• Limited material thicknesses: GMAW is not the best for very thick sections. It can handle heavier metals with the proper setup, but doing so consumes more power and needs experienced welders.

GMAW vs. other welding methods

Each welding method has specific characteristics that determine its optimal application. Here’s how GMAW compares:

• GMAW vs. TIG welding: GMAW is quicker and easier. You simply pull the trigger, and the wire feeds itself. TIG takes more skill because you control both the torch and a separate filler rod, but it gives beautiful, precise welds, especially on aluminum or stainless steel.
• GMAW vs. stick welding: GMAW makes smoother, cleaner welds, but it needs shielding gas and a clean surface. Stick welding can handle dirty or rusty metal and works great outdoors, though it’s slower and leaves slag to chip off afterward.
• GMAW vs. laser welding: Laser welding uses a focused beam of light for microscopic precision. It’s incredibly accurate but costly and primarily used in industries like aerospace, electronics, and medicine. GMAW is more affordable for most metalwork.

Safety tips for GMAW welding

GMAW welding operations require strict safety protocols:

1. Ventilation: Weld in a well-ventilated space or outdoors, or use an exhaust fan to pull fumes away when working indoors. A respirator with welding filters helps protect your lungs from metal particles.
2. Protective gear: Wear a long-sleeve shirt, welding jacket, welding helmet, welding gloves, and steel-toed boots. Your eyes also need safety goggles to protect you against UV from the arc.
3. Fire safety: Never weld near flammable materials like paper, wood, chemicals, or fabrics. Have a fire extinguisher rated for electrical and grease fires readily available. Assign someone to monitor and react fast in case of fires.

Summing up

Gas Metal Arc Welding (GMAW) is a widely used welding method in automotive, aerospace, shipbuilding, and metal fabrication industries. This process creates an electric arc between a continuously feeding wire electrode and the metal workpiece, melting both to form a strong joint. 

The essential equipment includes a power source, wire feeder, welding torch, shielding gas, and ground clamp. GMAW offers four transfer modes, allowing welders to adapt to various metal types and thicknesses.

The primary advantages of GMAW include fast welding speed, minimal heat distortion, easy learning curve, and versatility across different materials and positions. Compared to other methods, GMAW is faster than TIG welding, cleaner than stick welding, and far less expensive than laser welding. Safe operation requires adequate ventilation, complete protective equipment, and strict fire prevention practices.

Next steps with Standard Bots’ robotic solutions 

Looking to upgrade your automation game? Standard Bots Thor is built for big jobs, while Core is the perfect six-axis cobot addition to any automated operation, delivering unbeatable throughput and flexibility.

• Affordable and adaptable: Core costs $37k. Thor lists at $49.5k. Get high-precision automation at half the cost of comparable robots.
• Perfected precision: With a repeatability of ±0.025 mm, both Core and Thor handle even the most delicate tasks.
• Real collaborative power: Core’s 18 kg payload conquers demanding palletizing jobs, and Thor's 30 kg payload crushes heavy-duty operations.
• No-code simplicity: Our intuitive, no-code app makes it easy to teach Standard Bots robots to do everyday tasks. So, Core and Thor integrate smoothly with welding operations for advanced automation.
• AI-driven models: For complex, high-variance, and unpredictable tasks that are otherwise impossible to automate today, Standard Bots robots learn through our AI-driven vision-to-action models, similar to how full self-driving works.
• Safety-first design: Machine vision and collision detection mean Core and Thor work safely alongside human operators.

Schedule your on-site demo with our engineers today and see how Standard Bots Core and Thor can bring AI-powered greatness to your shop floor.

FAQs

1. What does GMAW stand for?

GMAW stands for Gas Metal Arc Welding. This welding process uses a continuously fed wire electrode and shielding gas to create strong, clean welds on various metal types.

2. Is it possible to weld without gas in GMAW?

No, GMAW requires shielding gas to protect the weld from contamination and atmospheric exposure. If you need a gasless welding option, flux-cored arc welding (FCAW) is a better alternative that uses a self-shielding flux core instead of external gas.

3. What are the common shielding gases used in GMAW?

The most common shielding gases are argon, carbon dioxide (CO2), and helium. Argon provides precision for thin materials, CO2 offers cost-effective deep penetration for thicker metals, and helium works well for high-heat applications on aluminum and copper.

4. Can GMAW be performed outdoors?

GMAW is not ideal for outdoor welding because wind can blow away the shielding gas and compromise weld quality. If you must weld outside, use a windscreen or enclosure to protect the welding area and maintain proper gas coverage.

5. What safety measures are essential in GMAW?

Essential safety measures in GMAW include wearing a welding helmet with proper lens shading, fire-resistant clothing, and welding gloves. You also need adequate ventilation to remove fumes and should maintain a safe distance from the arc to prevent burns and eye damage.