MIG (GMAW)

MIG (GMAW) creates strong continuous welds using a consumable wire electrode and shielding gas, ideal for fast, semi-automatic welding of steels and aluminum.

Overview

MIG (GMAW), or wire feed welding, uses a continuously fed consumable wire and shielding gas to join metals with a relatively clean, high-deposition weld. It works well on mild steel, stainless, and aluminum in the 1 mm to ~25 mm thickness range, with strong fillet and groove welds in many positions. The process is easily automated or semi-automated, which makes it a workhorse for production weldments and structural fabrications.

Choose MIG when you need good productivity, repeatable weld quality, and reasonable operator skill requirements. It excels in shop environments with proper fixturing, where you can control part fit-up and shielding gas coverage. Tradeoffs include higher spatter than TIG, limited access in very tight joints, and distortion that must be managed via design and fixturing. Weld appearance is good but not cosmetic-grade by default; post-grinding may be needed where aesthetics or precise dimensional control matter.

Common Materials

  • Mild steel A36
  • HSLA steel
  • Stainless steel 304
  • Stainless steel 316
  • Aluminum 5052
  • Aluminum 6061

Tolerances

±0.03" to ±0.06" on welded assemblies with proper fixturing; weld size typically held within ±1/16"

Applications

  • Structural steel frames and skids
  • Automotive and trailer chassis components
  • Equipment bases and machine frames
  • Agricultural and construction equipment weldments
  • Handrails, guards, and brackets
  • General fabrication of box sections and frames

When to Choose MIG (GMAW)

Use MIG (GMAW) for welded steel or aluminum parts where productivity, repeatability, and moderate appearance matter more than ultra-precise bead control. It fits small to high-volume weldments with material thicknesses from sheet to medium plate. It is best when parts can be fixtured in a shop environment with reasonable access to the joint.

vs TIG (GTAW)

Choose MIG over TIG when you need higher deposition rates, faster cycle times, and lower operator skill for structural or production weldments. MIG is better for thicker sections and long fillet welds where ultra-fine bead control or cosmetic appearance is not critical.

vs Stick (SMAW)

Choose MIG over Stick when you’re welding in a shop with power and gas available and want higher productivity, less cleanup, and better performance on thin to medium sections. MIG is ideal for repetitive production weldments where changing rods and chipping slag would slow you down.

vs Resistance Welding

Choose MIG over resistance welding when you have thicker materials, non-overlap joints, or complex weld paths that spot or projection welding can’t reach. MIG suits lower to medium volumes and structural weldments where joint strength and flexibility of joint design matter more than cycle time in the milliseconds range.

vs Laser Welding

Choose MIG over laser welding when joint fit-up is less precise, parts are heavier-gauge, and you don’t want the capital cost and tight tolerance requirements of laser systems. MIG is more forgiving of gaps and alignment errors and works well for robust structural assemblies.

vs Adhesive Bonding

Choose MIG over adhesive bonding when you need high structural strength, good performance at elevated temperatures, and immediate load-bearing capability. MIG gives a metallic joint with well-understood design rules where surface cleanliness and cure time constraints of adhesives would be a problem.

Design Considerations

  • Provide clear weld symbols and specify weld size and length instead of generic notes like “weld all around” to avoid over-welding and cost creep
  • Design joints for good torch and wire access, targeting flat or horizontal positions where possible to reduce labor and improve quality
  • Use consistent material thicknesses and simple joint preps (e.g., lap, T, single bevel) to simplify fit-up and fixturing
  • Control gaps at joints; aim for tight, repeatable fit-up to reduce heat input, distortion, and rework
  • Keep critical machined surfaces away from heavy welds or plan machining after welding to recover dimensional accuracy
  • Minimize unnecessary weld length and avoid oversized fillets; oversized welds add heat, distortion, and cycle time without meaningful strength gain