Choosing a MIG welder for trade use comes down to one question: will it keep welding for as long as your job needs it to, day after day, without stopping to cool down. Everything else on the spec sheet, wire feed, torch type, control panel, sits underneath that one fact.

What duty cycle actually tells you

Duty cycle is the share of a ten-minute period the machine can weld at a given output before its internal temperature forces it to stop and cool. A machine rated at 200A/30% duty cycle can run at 200A for three minutes in every ten before it cuts out. Push it harder than that and it protects itself by shutting down mid-weld, which is not a fault, it is the machine doing exactly what the datasheet said it would.

The figure that matters is your amperage

Retailers lead with the peak output figure because it looks impressive. It is rarely the number a working welder needs. What decides whether a machine suits your day is the duty cycle at the amperage you actually run for most of a job. A machine that welds all day at 140A might still cut out repeatedly if you spend most of your time at 180A, even though 180A is well within its rated maximum.

Reading a datasheet properly means checking duty cycle at more than one output figure, where the manufacturer publishes it, and matching that against your typical working amperage. A full explanation of how these figures are built and where they mislead is covered on Duty Cycle Explained.

Why this figure decides the rest of the purchase

Once you know the duty cycle you actually need, most of the other decisions follow it. A higher sustained duty cycle generally means a heavier transformer or a beefier inverter, which affects weight and portability. It also often pushes the machine's power requirement from a standard 230V single-phase supply toward three-phase, which is worth confirming before the machine arrives on site. The trade-offs between single-phase and three-phase machines are set out on Single Phase vs Three Phase Welders.

Work out your typical welding amperage first. The duty cycle you need follows from that, and the rest of the specification follows from the duty cycle.

The price gap between a budget MIG welder and a mid-range one usually comes down to a single figure: duty cycle, the share of a ten-minute period the machine can actually weld at a given amperage before it has to stop and cool. A budget machine and a mid-range machine can put down the same weld on the same steel. What differs is how long each one can keep doing it before the thermal cutout kicks in.

When the cheaper machine holds up

If your welding is intermittent, a budget machine is not a compromise, it's the right tool. That covers a fair amount of trade work: repairs, brackets, fabrication jobs measured in minutes, site fixes between other tasks. In that pattern the machine spends most of its time off, and duty cycle at your working amperage is rarely the limit you hit.

• Occasional repair or maintenance welding
• Thinner gauge material where the working amperage sits well under the machine's rated maximum
• A second machine kept for site work while a better-specified one stays in the workshop
• A trade where welding is one task among several

In each of these, paying more buys headroom you won't use.

Where it turns into a false economy

The condition that flips this is hours in the arc. If you're running structural steel most of the day, or any job where the welder is genuinely working for long stretches, the duty cycle gap between a budget machine and a mid-range one stops being theoretical. The budget machine cuts out, you wait for it to cool, and the job takes longer than the price tag suggested it would.

The same applies where the work regularly pushes the machine near its rated maximum output. A machine rated for a given amperage at a low duty cycle is not lying about what it can do, it's telling you exactly how little of a working hour it can do it for.

The other side of the price tag

Spares and service network matter here too. A budget machine that's cheap to buy and expensive to keep running, because parts are slow to source or don't exist for that model, is a different kind of false economy from a duty cycle shortfall. Worth checking before you buy.

For a fuller look at what duty cycle figures mean once you're welding for a living, see the guide on duty cycle explained. If your power supply is part of the decision, the guide on single-phase vs three-phase welders covers the other half of it.

The price on the box is the smallest number in what a MIG welder actually costs you over three or four years of daily use. The larger figure is what you spend keeping it running: consumables, the odd repair, and the wait for a part when something fails.

What wears out first

Torch consumables go first on any machine, whatever the brand. Contact tips, nozzles and liners wear with normal use and need replacing as a matter of course. Drive rollers wear more slowly but still wear, particularly if you run flux-cored wire through them regularly.

Beyond consumables, the parts that actually fail under load are the wire feed motor, the torch trigger switch and the contactor that switches the welding current. None of these appear on a retailer's spec sheet, because they only become relevant once the warranty has run out. Running a machine near the top of its duty cycle day after day is what shortens their life, far more than light or occasional use does.

Consumables and spares are not the same question

Consumables can usually be sourced from several suppliers regardless of brand, since tip and nozzle sizes are broadly standard across torch types. Spares are a different matter. A feed motor, a control board or a torch assembly is brand-specific and often model-specific, and that is where the difference between manufacturers actually shows up.

What to check before you buy

• Search for the exact spare part for the model before you commit to it.
• Check whether spares come directly from the manufacturer or only through a wider distributor network, and how that affects lead time.
• Ask what a repair typically involves for that model: whether it can be done on site or has to be sent away.
• Note the torch fitting used. A common fitting widens your consumable options; a proprietary one narrows them.

A machine with a thin spares network is not automatically the wrong choice. If your use is light and occasional, you may never need a part beyond consumables. If the machine is working daily and close to its rated duty cycle, spares and service turnaround are worth confirming before the machine arrives.