Start from the chart, finish by ear
Every machine prints a table inside the wire compartment: thickness against voltage and feed. Start there. Then run a bead on scrap of the same thickness and listen — a correct MIG arc makes a steady, even crackle, often described as frying bacon. A hiss with spatter means too much voltage; a stuttering, popping arc that pushes the gun back means too much wire.
Reading the bead
Too little heat and the bead sits proud on the surface with a rounded profile — it will lift off with a chisel because nothing fused. Too much and you get undercut along the edges, or a hole. The correct bead is slightly domed, evenly rippled, and fused into the parent metal at both toes.
Change one thing at a time
The commonest mistake is turning both dials at once and losing the reference. Set voltage for the thickness, then adjust wire speed until the arc note steadies. On a synergic machine the second dial follows the first, which is exactly what makes those machines easier to learn on.
Stick-out matters as much as the dials
Hold the nozzle so about 10 mm (0.39 in) of wire is exposed. Too long and the arc becomes cold and wandering regardless of settings; too short and spatter blocks the nozzle. Many « the machine will not weld » complaints are stick-out rather than voltage.
The questions welders ask
Why do my settings work one day and not the next?
Usually the contact tip. Its bore goes oval before it looks worn, and the arc wanders as a result — so the settings that worked yesterday appear wrong. Change the tip before touching a dial. After that, look at the wire: a spool that has sat in a damp workshop feeds differently from a fresh one.
Should I push or pull the gun?
Push for MIG under gas — angling the gun so it points forward into the direction of travel keeps the shielding gas over the pool and gives a flatter bead with less penetration. Pull for gasless flux-cored, where dragging keeps the slag behind the pool. Getting these the wrong way round produces porous, dirty welds on either process.
Last reviewed 2026-08-14
