The MIG welding process is efficient due to its ability to feed welding wire through the electrode. This allows for longer weld times and increased productivity. Unlike other welding machines that use a stinger, the MIG uses a gun to lead wire into the weld puddle. MIG guns require parts that other welding machines do not, and these additional parts are subject to wear. A MIG gun has a liner that guides the wire through the lead and out the nozzle of the MIG gun. When the liner becomes damaged or wears from long-term use, it needs to be replaced.
Turn off the power switch on the MIG welding machine, disconnect the power supply, and turn off the gas. Disconnecting the power supply is to maintain your safety while exchanging the MIG gun liner. If the MIG machine's power is turned on while you are performing the liner exchange, you may receive an electric shock. Back roll the wire inside the MIG lead and thread the wire into the holes on the spool to keep it from unspooling.
Gain access to the nut that holds the MIG casing in place. Internal spooled MIG machines have a door that opens to access the spool and MIG lead. External spooled machines will require you to use a ladder or lower the spool arm to release tension on the nut. Disconnect the trigger control from the MIG welding machine.
Pull the cup off the MIG gun and set it aside. Loosen the copper tip with the needle nose pliers and place it with the MIG cup. Remove the liner holder with the adjustable wrench to free the MIG gun liner. Lay the MIG gun casing flat on a table or the floor. Grab the liner with the needle nose pliers from the end that you disconnected from the welding machine and pull gently. The liner will slide without a lot of pressure. Remove and dispose of the liner.
Blow out the inside of the MIG casing to remove debris. If debris gets lodged inside of the liner, the wire will not feed correctly. Insert the new MIG gun liner, while the MIG gun lead is still laying flat on the table. Work the liner in slowly. The liner may bind up when it reaches the MIG gun. Twist the liner while applying pressure forward to release the bind. Push the liner until it is 3/4 inch beyond the MIG tube. Cut off the excess liner with the wire cutters.
Reassemble the MIG gun. Attach the MIG lead to the welding machine and reconnect the trigger control. Thread the MIG wire through the drive rolls and into the end of the liner. Re-clamp the drive rolls to hold the wire in place. Reconnect the power supply to the welding machine and turn the MIG welding machine on.
Turn up the wire speed on the MIG and press the trigger on the MIG gun until the wire exits the copper tip. Trim the excess wire with the wire cutters and reset your welding machine to begin welding.
