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Expanded metal is easy to weld badly. The thin strands heat quickly, the open pattern provides little support, and every unnecessary pass adds shrinkage that can pull the sheet out of shape. A suitable MIG welder helps, but technique and fixturing matter just as much. For most expanded-metal work, the best setup is a small inverter MIG welder with adjustable voltage, wire speed, inductance or arc control, and a reliable low-amp range.
What Makes a MIG Welder Suitable for Expanded Metal
Look for a machine that can produce a stable arc below about 100 amps. Many expanded-metal sheets are between 16 and 22 gauge, although heavier flattened or raised patterns may be 14 gauge or thicker. A welder that starts at 30 or 40 amps is easier to control than one that has a harsh minimum output of 60 or 70 amps.
Wire size matters. Use .023-inch solid MIG wire for thin sheet, .030-inch wire for general-purpose work, and .035-inch wire only when the material is heavy enough to absorb the extra heat. Smaller wire requires less current to melt and makes short tack welds easier. A machine with a spool of .023-inch wire and a 75/25 argon-carbon dioxide gas mix is usually the most forgiving combination.
A 120-volt inverter MIG welder with gas capability is sufficient for light expanded-metal panels, guards, screens, and repair work. Choose a 240-volt unit if you also weld frames, brackets, or tubing thicker than 1/4 inch. Extra power is useful for the surrounding frame, but it does not make a thin sheet safer to weld.
Best Welder Types for the Job
| Welder type | Best use | Advantages | Limitations |
|---|---|---|---|
| 120V inverter MIG | Thin expanded metal and light frames | Low minimum output, portable, inexpensive to run | Limited duty cycle and penetration on heavy steel |
| 120/240V dual-voltage MIG | Mixed sheet, tubing, and structural repairs | More range, better long-term flexibility | Costs more; high output is unnecessary for the mesh itself |
| Flux-core MIG | Outdoor work or dirty steel | No shielding-gas bottle, better wind tolerance | More spatter and heat; easier to burn through thin mesh |
| Stick welder | Heavy frames and outdoor repairs | Simple and effective on thick steel | Usually too hot and cumbersome for thin expanded metal |
A dual-voltage MIG machine is the best all-around purchase if expanded metal is only one part of your work. It lets you run a controlled low-current arc on the mesh and switch to 240 volts for heavier plate. If you only build small panels, a cheaper 120-volt MIG is fine and may actually be easier to use.
Starting Settings That Limit Warping
Use the lowest setting that gives a clean tie-in to the surrounding frame. For 18- to 20-gauge expanded metal, start around 35 to 60 amps with .023-inch wire, then adjust wire speed according to the machine’s chart. For 16-gauge material, roughly 60 to 90 amps with .023- or .030-inch wire is a reasonable starting range. These are starting points, not universal settings; pattern size, steel coating, joint fit, and welding position change the result.
Use short-circuit transfer rather than spray transfer. Spray transfer requires substantially more current and will rapidly overheat thin strands. Set the gas flow near 20 cubic feet per hour indoors, increase it only when necessary, and keep the nozzle close enough to maintain shielding without dragging it through the openings.
Make tacks no longer than about 1/4 inch at first. If the mesh is very thin, use a series of quick trigger taps instead of one continuous bead. Let the area cool until it is no longer visibly hot before adding the next tack. A short weld followed by cooling is slower than running a continuous bead, but it prevents the panel from pulling into a bowl shape.
Setup and Fixturing Matter More Than Maximum Amperage
Expanded metal must sit tightly against its frame. Gaps force you to bridge unsupported openings, which concentrates heat and causes burn-through. Use clamps every 6 to 10 inches on straight sections, and add temporary flat bars or copper backing where the pattern allows it. Copper absorbs heat and will not fuse readily to steel, making it useful behind small openings.
Clean mill scale, oil, paint, and galvanized coating from the weld area. Galvanized expanded metal requires particular care: remove the coating well away from the weld zone, provide strong ventilation, and use appropriate respiratory protection. Zinc fumes can cause metal fume fever. Do not weld coated material in an enclosed space simply because the welds are small.
Tack the panel at the center of one side, then the opposite side, followed by the remaining sides. Continue alternating locations rather than welding around the perimeter in one direction. For a large panel, divide the work into sections and skip around so heat does not accumulate in one corner.
Features Worth Paying For
Prioritize a smooth wire-feed mechanism, a good torch liner, an adjustable inductance or arc-control setting, and a clear voltage and wire-speed chart. A machine with separate voltage and wire-speed controls is preferable to a basic tapped-voltage unit because small adjustments are important on mesh.
A dual-voltage MIG welder with inductance control is worth considering when you weld different thicknesses. Lower inductance can produce a sharper, more forceful arc; higher inductance generally softens the arc and can reduce spatter. The useful setting depends on the wire, gas, and joint, so treat the control as a tuning aid rather than a cure for poor fit-up.
Do not pay extra for a 250-amp machine solely to weld expanded metal. That output is valuable for thick structural work, but the mesh will usually warp or burn through long before a small welder runs out of power. Spend the difference on clamps, a gas regulator, quality wire, and a proper auto-darkening helmet. A quality auto-darkening welding helmet with grind mode makes it easier to inspect each short tack without repeatedly lifting the hood.
Common Failure Modes
Burn-through usually means the arc is too hot, the travel speed is too slow, or the mesh is not supported. Reduce wire size and output first; do not solve the problem by increasing shielding gas. Porosity points to wind, contamination, a blocked nozzle, or insufficient gas flow. Excessive distortion usually comes from long welds, poor clamping, or welding one side continuously.
If the mesh is only being attached to a solid frame, weld intermittently. Tacks spaced 2 to 4 inches apart are often adequate for nonstructural screens, while load-bearing work requires a design based on the frame, mesh gauge, and applicable code. Expanded metal should not be treated as a structural substitute for plate or properly sized bar.