MIG (GMAW)

MIG (GMAW) joins metals with a continuously fed wire electrode and shielding gas, delivering fast, robust welds with moderate heat input and cleanup.

Overview

MIG (GMAW) is an arc welding process that feeds a consumable wire through a gun while shielding the weld pool with gas (typically Ar/CO₂ mixes). It’s one of the fastest ways to produce strong welds on carbon steel, stainless, and aluminum, and it adapts well to manual, robotic, and fixture-based production.

Choose MIG when you need repeatable structural welds, good deposition rate, and reasonable fit-up tolerance for fabrication work. It handles fillets and groove welds efficiently on plate, tube, and formed parts, and it’s commonly used for short-run and production welding.

Tradeoffs: heat input can distort thin sections, spatter and cleanup are common (especially short-circuit transfer), and outdoor/windy environments can compromise shielding gas. Precision cosmetic weld appearance and very thin-gauge control are harder than with TIG, and joint prep still drives quality and cost.

Common Materials

  • A36 steel
  • 1018 steel
  • 304 stainless
  • 316 stainless
  • Aluminum 6061
  • Aluminum 5052

Tolerances

±0.030" to ±0.060" (welded fabrication after fixturing; tighter typically requires post-machining)

Applications

  • Structural steel frames and bases
  • Welded sheet metal enclosures
  • Truck and trailer components
  • Handrails and guard structures
  • Aluminum brackets and supports
  • Robotic production fillet weldments

When to Choose MIG (GMAW)

MIG fits parts that need strong, repeatable welds at moderate to high throughput on steel, stainless, or aluminum. It’s a good choice when joint fit-up isn’t perfect but you can fixture parts to control distortion and maintain geometry. It scales well from prototypes to production, including robotic cells when volume justifies fixturing.

vs TIG (GTAW)

Choose MIG when deposition rate and throughput matter more than maximum weld appearance and pinpoint heat control. MIG is typically faster on fillet and groove welds in thicker sections and is easier to automate for consistent production.

vs Stick (SMAW)

Choose MIG when you can control the environment and want higher productivity with less operator fatigue and faster learning curve. MIG also reduces slag removal and supports continuous welding, which helps on long seams and repeatable assemblies.

vs Resistance Welding

Choose MIG when the joint isn’t a simple lap joint on thin sheet or when you need longer seams, thicker material capability, or 3D tubular/plate fabrications. MIG works well when spot-weld electrode access is limited or when you need continuous, sealed joints.

vs Laser Welding

Choose MIG when part fit-up varies, gaps are present, or you’re welding thicker sections where high deposition is needed. MIG usually has lower equipment cost and is more forgiving in job-shop fabrication with mixed part geometries.

vs Brazing & Soldering

Choose MIG when the joint must carry high structural loads and base-metal strength is required at service temperature. MIG produces a true fusion weld, while brazed/soldered joints rely on filler bonding and typically have lower strength and temperature limits.

Design Considerations

  • Specify weld symbol details (size, length, intermittent vs continuous, all-around) and inspection requirements so the shop can quote consistently
  • Design joints to be self-locating and fixture-friendly (tabs/slots, hard stops, consistent datums) to control weld distortion and assembly variation
  • Avoid long continuous welds when not required; use intermittent welds or stitch patterns to reduce heat input, distortion, and cycle time
  • Call out post-weld machining surfaces and leave stock where needed; don’t rely on as-welded dimensions for tight fits
  • Provide realistic gap/fit-up tolerances and edge prep notes for groove welds; joint prep often dominates cost and quality
  • Plan access for the gun and nozzle (clearance, line-of-sight, and travel path) and avoid deep pockets that trap spatter and fumes