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Choosing A MIG Welder

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Key considerations

What amperage machine is required to to do the job? Presume 35 to 40 amps per millimetre to be welded.
What material will be welded? mild steel, stainless, aluminium & any others?
Synergic or synergic pulse ? Most machines are now synergic & have pre-programmed settings according to type of material & diameter. Having a pulse facility is a significant benefit, when welding stainless & aluminium.
How easy is the interface on the machine to operate? A simple set up & the ability to store frequent tasks to memory is essential.
What is the duty cycle of the machine? Check the duty cycle isn't too low (We explain more in our article below). Water cooling maybe needed for heavy duty, time on applications.
What is the wire drive system specification? 2 or 4 roll? The rollers are typically V grooved, but should be switched to U groove for aluminium. Make sure the drive block & rollers are durable.
What is the MIG torch specification & length? Check the torch amperage is sufficient for the job. Liners & contact tips will need changing if you are welding stainless or aluminium.
What input power do you have available? You will be limited on output if you have a 240 volt supply. Maximum amperage output on 240 volt is typically 200 amps, allowing you to weld up to 6mm.
How good will the after sales service be ? Is there a local distributor with engineers who can site visit?

Fan on Demand : This feature lowers running costs and reduces contamination to internal components. The fan kicks in when its needed, rather than running all day.
Printed Circuit Board Protection; If the Machines PCB's are protected from dust & kept away from the fan, reliability will increase. Some manufacturers have the parts that need cooling in a duct type housing & the PCB isolated separately.
MIG wire inch button; Saves wasting your shielding gas when feeding wire through at the start of a new reel.
Gas Purge button; Another nice option. Save yourself some MIG wire, when you're setting your gas flow.
Burn Back; Not all machines have this externally, but it is good to be able to trim the burn back to the wire according to the application & operator.

Drive Block Systems; Four roll would always be first choice, but some of the lower amperage machines won't have them, meaning two roll would be more acceptable.
Budget; How much welding are you going to undertake? Gear your purchasing decision around jobs you'll do most.
Polarity Changeover; A lot of welders at the light industrial end will be able to weld with gasless flux cored MIG wire. Is the switch over easy on the machine you're considering?
Duty Cycle Testing; MIG welders tested at 20 degrees & 40 degrees we consider good. Beware any manufacturer who doesn't quote an ambient temperature for testing duty cycles. Light industrial machine duty cycles can be as low as 20% but heavier ones should range between 40-60%. However a 300amp MIG with a 30% duty cycle is acceptable.

Digital Meters Factory Fitting; Great to have when you purchase and may be required for calibration requirements. To fit them retrospectively could be costly.
Availability of spares/after sales service ; Ask where the machine is manufactured. Even recognized brands outsource their production, which can lead to quality and after sales issues with a lack of continuity around supply for spares.
Selecting the correct amperage machine; Generally, you should work on 35-40 amps per 1.0 mm diameter of material to be welded.
Manufacturers Warranty; This is a great guide to quality. A three year warranty is good cover, five years exceptional. Be sure to return your registration.
Weld Characteristics; Make sure the arc is smooth and that it is suitable to your choice of application.

Drive Rollers; Metal rollers are the best, nylon and plastic ones will always wear quicker. Choose the groove of the roller according to material. It's V grooved for mild steel/solid wire, V knurled for flux cored & U grooved for aluminium.
Bottle Trolley; If you want a MIG to be portable, you'll need one. If you have a full size cylinder, check that the running gear is sturdy enough.
Inverters; All inverters are step less and so have infinite control. With traditional stepped voltage machines no longer manufactured, inverters also offer power saving.
Synergic; Synergic MIG's are pre-programmed & easy to set up, but don't necessarily have pulse. Checking the ease of set up & the ability to store frequent welding tasks to memory is a must before purchase. You should be able to dial in the material & the diameter.
Pulse MIG; Pulse MIG reduces heat input, lowers spatter & reduces welding fume.