Using a MIG welder comes with very minimal requirements and a few things to master. Follow this simple sequence and you’ll quickly be on your way to laying down decent quality welds.
Step #1: Get the Right Welding Wire
Make sure you’re using the right electrode wire — either gasless flux core wire or a gas-shielded metal wire. Set up your wire spool and wire tension so the gun feeds wire smoothly. For most basic steel welding applications the wire diameter should be between 0.25 and 0.35 inch.
Step #2: Set Up Your Gas Supply
If you’re welding with solid electrode wire using the gas-shielded MIG welding method (GMAW) you will need a cylinder full of the right shielding gas, a gas regulator, gas feed line and the correct gas flow, as follows:
- Shielding Gas: 75% argon / 25% carbon dioxide mix for welding steel, 100% argon for welding thin aluminum, argon / helium mix for thicker aluminum. You can get a gas cylinder pre-filled from your local welding supply store such as AirGas, Harris Gas, etc.
- Gas Regulator: set this to 22-25 cubic feet per hour flow rate
- Gas Line: set this up according to the manufacturer’s directions. One end should plug easily into the gas regulator, and the other end should plug right into your MIG machine.
Step #3: Prepare the MIG Gun
Once you have placed the electrode reel on the spool feed and set the right wire tension, now it’s time to prepare your MIG gun. Screw the copper contact tip into the end of the gun. Then screw the correct gas shielding tip on — this will be a narrower cone for flux-cored wire or a wider tube for solid metal wire.
Turn on the machine, but don’t turn on the gas yet. Feed the electrode wire through the MIG gun by pulling the trigger until the wire sticks out out of the contact tip for about 1/4 inch.
IMPORTANT! Do NOT touch any metal with the wire as you do this or you will start welding whatever you touch. Do NOT push the wire through the feed cable to the gun, as you are likely to kink the wire or damage the inside of the feeder tube.
Step #4: Configure the MIG Machine Settings
You need to configure your MIG machine to baseline on three key settings:
- Polarity: The polarity setting is the driving force that controls the electronic signal and melts the electrode wire into the molten weld puddle. There are two different settings for polarity, Direct Current Electrode Positive (DCEP or “Reverse Polarity”) or Direct Current Electrode Negative (DCEN). DCEP is the standard MIG setup, tends to have a more stable arc, and is suitable for thicker materials. DCEN is best used for thinner sheet metal. Welding aluminum requires DCEN.
- Voltage or Amperage: This controls the amount of current running through the electrode wire into the base metal. Higher voltage or amperage will generate a hotter arc that melts the wire faster and penetrates deeper for thick metal. Lower voltage or amperage will generate a cooler arc that melts the wire more slowly and penetrates shallower for thin metal.
- Wire Speed: The wire speed setting controls how fast the electrode wire feeds out of the tip of the gun and into the molten weld puddle. At lower voltage / amperage settings and when welding thin metal you want a slower wire speed. For higher voltage / amperage settings and thicker metals you want a faster wire speed.
Almost all MIG machines come with a detailed configuration table that shows you the correct baseline polarity, voltage / amperage, wire diameter and wire speed settings for different metal types and thicknesses. We strongly urge you to start with these baseline settings, then run some test welds to optimize them for your particular situation.
Step #5: Prepare the Weld Area and Metal Pieces
Now it’s time to prepare the area you’re welding and the metal pieces you’re planning to weld. ONLY start welding once your work pieces fit nicely together and you’ve got clean bare metal to weld. Otherwise you will end up with a weak, porous weld that will fail.
Remove anything flammable cfrom the area and make sure the welding surface is clear of oil, grease and dust. Ideally, you want to weld on a table with a metal top so you can clamp the ground directly to it.
Clean up your metal pieces, making sure there is no paint, dirt, grease or rust within an inch or two of the weld. Use a degreaser, then grind, sand or wire brush the area clean until you get bare metal on all sides of the joint.
If you’re welding thicker metal or metal tube, you will need to chamfer the edges. Ensure your metal pieces fit as tightly as possible, and use clamps, welding magnets and/or tape to hold things in place while you weld.
Finally, make sure you’ve got a fire extinguisher handy. Accidents happen and you don’t want your garage, shop or barn going up in flames!
Step #6: Put On Your Safety Gear
Before you start working with your MIG welder, put on your PPE:
- welding helmet
- welding jacket
- welding gloves
- steel-toe boots
Make sure all your PPE is flame-resistant as you’ll be working with an extremely hot electric arc, hot metal and molten metal drops.
Step #7: Start Welding!
Set yourself up so you’re comfortable, have a good view of the joint you’re planning to weld, and can control the gun tip with precision. Make sure the gun isn’t hung up on anything, your MIG machine is turned on, the gas is flowing, the wire is trimmed to the right length, and you’re holding the gun tip the correct distance from the work.
Practice your welding movement a few times before pulling the trigger. This helps get you “in the groove” with your planned welding pattern, and to identify any issues before you start.
When you’re ready, go ahead and start your weld. Work methodically using the tip pattern you want, making sure the weld puddle is moving smoothly and your MIG is making a nice sizzling sound (no popping or spattering).
Step #8: Evaluate Your Welds and Adjust
Keep iterating and troubleshooting your weld quality as you go. Make the right adjustments and you’ll have good quality welds soon enough!
We hope this MIG welding checklist for beginners has helped you get started in the right direction!
Nick Klamecki is a certified Fire and Workplace Safety expert with 15 years experience in product research and testing. He has a degree in Economics from U.C. Davis, is an active outdoorsman and spent years ensuring the safety of special needs children. Nick researches and tests workplace, industrial and safety products and provides advice on their safe use.