By: Jared McCombs
MIG= Metal Inert Gas Welding
An arc is struck between an electrode and
the sheet metal to be welded. The
electrode used in the machine shop is
Copper wire and is in the form of
continuous filler metal. The weld is
shielded by an inert gas, CO , to prevent
• Carbon steels, low alloy steels, stainless steels,
most aluminum alloys, and zinc based copper
alloys can be welded with the MIG Welder.
• Can weld very thin sections and metals that can
not be easily welded with other types of welding.
• Always wear non-flammable, non-synthetic
clothing when welding. (i.e. cotton).
• Ensure area is properly ventilated.
• Always wear welding gloves, a welding helmet,
and a shop coat.
• Ensure the piece you are welding is safe to weld
(i.e. a container containing flammable liquid).
• Caution: Some materials (i.e. galvanized
materials) can become toxic when welded, so try
to scratch off the toxic material and ventilate the
area as much as possible.
• Caution: Welding produces high temperatures
even after welding is completed.
Setting up the Machine
• Choose the correct wire gage based
on the type of material and thickness
of weld. You can determine the proper
wire gage by calling companies Aluminum
(i.e. Oxarc) or looking up information in
tables. Keep in mind, tables change
often due to new material discoveries.
• Set the wire speed and thickness dials
to appropriate settings. (Lift up the
hood to find the wire speed and
thickness settings in a table.)
• Turn on the MIG welder.
• Open valve on CO2 tank to form an
inert gas shield.
• Ground the welder to the table using
• Turn the ventilation fan on using the
switch on the wall.
Setting Up Demonstration
Person enters welding area, and demonstrates the following process:
1. Turn on ventilation fan
2.Set the wire speed and thickness dials to appropriate settings. (Lift up the hood to find the wire speed and thickness
settings in a table.)
3.Turn on the MIG welder.
4.Open valve on CO2 tank to form an inert gas shield.
5.Ground the welder to the table using the clamp.
The following is the correct procedure for setting up the mig welder. First, make sure the ventilation is turned on at all
times while using the mig welder. Next, set the wire speed and thickness dials to appropriate settings. You can find
approximate settings on the inside cover of the welder. Turn on the mig welder. Open the valve on the CO2 tank.
Ground the welder to the table or the part. (make sure to say the script simultaneous with actions)
• Prep surface to ensure a clean strong
• Put on all safety gear.
• If the wire is protruding 1 cm past the
nozzle, break it off on the table. Do not
leave it stuck to the table.
• Ensure others around you know you are
welding by saying, “COVER!”
• Hold the tip of the electrode against the piece
being welded and pull the trigger until an arc is
created between the electrode and the work
• When MIG welding, push the electrode along the
surface while slowly rotating wrist from side to
• It is important to be comfortable and have a
steady hand while welding. You can use both
hands to keep the torch steady.
The purpose of this slide will be to demo the the proper and improper techniques of mig
welding. First have welder do a proper smooth and steady weld. Next demo a weld which the
welding speed is to slow and the weld burns through. Next demo a weld which is to fast and
does not penetrate through the material. Last, re-demo the correct techniques.
Script: We will now look at proper and improper techniques of mig welding. As you can see
the welder uses a steady smooth motion, moving the torch along the surface of the part. You
can see the bead has consistent properties along its axis. You can hear the welder is making
a sound like frying bacon.
In this demo you will see the welder using a motion that is too slow. The weld is burning
through and leaving holes in your part. The welder should increase speed.
In this demo you will see the welder using a motion that is too fast. You can see that the bead
is thin, and has inconsistent properties along its axis. The welder should decrease speed.
(show a good weld again) Remember that as you weld, take a deep breath, relax, count to
10, and use a steady motion.
• Turn off the power to the welder.
• Close the valve on the CO Tank.
• Wrap the ground cable around the welder.
• Wrap the torch around the welder.
• Unplug the welder from the socket and wrap the
cord around the welder.
• Turn off the ventilation fan with the switch on the
• Put away the helmet, gloves, and shop coat.