This document provides an overview of gas metal arc welding (GMAW), also known as metal inert gas (MIG) welding. It discusses GMAW safety, the basic principles and components of the GMAW process, how to set up GMAW equipment, important welding variables, and the advantages of GMAW. Key aspects covered include the use of a solid wire electrode and shielding gas, the electric arc between the wire and workpiece, and how to adjust variables like wire feed speed, voltage, and gas flow rate.

1. GMAW / Mig Welding
Munim Shaukat (Lecturer)
Mechanical Engineering Department
University of Lahore

2. Over view
a During this overview, we will discuss the
following topics:
• Safety
• GMAW Basics
• Equipment Set-Up
• Welding Variables
• Process Advantages and Limitations

3. GMAW Safety
a ‘GMAW Safety’ is supplemental and does
not replace the information found in ‘Arc
Welding Basics’

4. a Fumes and Gases can be dangerous
• Keep your head out of the fumes
• Use enough ventilation, exhaust at the arc, or both, to keep
fumes and gases from your breathing zone and the general
area
• Local exhaust and mechanical ventilation can be used
without reducing weld quality
a Electric Shock can kill –
• Do not touch the electrode or metal parts of the electrode
holder with skin or wet clothing
• Keep dry insulation between your body and the metal being
welded or ground
• The coil of wire is ‘electrically hot’ so do not touch it.

5. a REMEMBER – Gas Cylinders require SPECIAL safety
precautions
• Cylinders must be secured in an upright position
• Cylinders should be located in an area away from arc
welding, cutting, heat, sparks, and flame

6. GMAW Principles
a GMAW stands for Gas Metal Arc Welding
a GMAW is commonly referred to as MIG or Metal Inert
Gas welding
a During the GMAW process, a solid metal wire is fed
through a welding gun and becomes the filler material
a Instead of a flux, a shielding gas is used to protect the
molten puddle from the atmosphere which results in a
weld without slag
a GMAW is the most widely used arc
a welding process in the United States

7. GMAW Circuit
a Three things happen when the GMAW gun trigger is
pulled:
• The wire electrode begins to feed
• The circuit becomes electrically ‘hot
• Current flows from the power source through the gun
cable, gun, contact tip to the wire and across the arc. On
the other side of the arc, current flows through the base
metal to the work cable and back to the power source
– Shielding gas flows through the gun and out the nozzle

9. GMAW Components
a DC or Direct Current power supply
a Electrode or wire feed controller
a Wire drive roller assembly
a Shielding gas source (cylinder) & regulator
a Manually held Gun & ground clamps
a Wire reel

10. 1 - Electrode
a A GMAW electrode is:
• A metal wire
• Fed through the gun by the wire feeder
• Measured by its diameter

11. 2 - Arc
a An electric arc occurs in the gas filled space
between the electrode wire and the work
piece
aElectric arcs can
generate temperatures up
to 10,000°F

12. 3 - Weld Pool
a As the wire electrode and work piece heat up and melt,
they form a pool of molten material called a weld pool
a This is what the welder watches and manipulates while
welding

13. 4 - Shielding Gas
a GMAW welding requires a shielding gas to protect the
weld puddle
a Shielding gas is usually CO2, argon, or a mixture of both
aThe gauges on the regulator
show gas flow rate and bottle
pressure

14. 5 - Solidified Weld Metal
a The welder “lays a bead” of molten metal that
quickly solidifies into a weld
a The resulting weld is slag free
aAn aluminum weld done with
the GMAW process

15. GMAW Equipment Set Up
1. Connect work clamp
2. Select electrode
a. Type
b. Diameter
3. Select shielding gas
4. Turn power supply on
5. Adjust machine output
a. Wire feed speed
b. Voltage
6. Adjust gas flow rate

16. GMAW Process Variables
a Welding variables
• Wire Feed Speed (WFS)
• Voltage
a Operator controlled variables
• Travel speed
• Gun angles
• Contact tip to work distance
(CTWD)
• Gas flow rate

17. GMAW component diagram

18. GMAW Advantages
• Welding can be done in all positions
• No slag removal required
• High efficiency
• Less work piece distortion
• Large gaps bridged easily ,
• High Weld Quality

19. Typical Setup for voltage
• The GMAW machine is a “Constant Voltage”
power supply. This is set using the voltage dial
• This setting can be monitored by the “Volt” meter
on the front panel of the welder
• Ideal voltage settings can be found in the wire
manufactures data book

20. Typical Setup for Wire speed
• The wire feed rate or speed is set using the dial on the wire
controller This setting increases or decreases current or
“Heat”. This setting is measured in AMPS or IPM
(inches per minute )
• Ideal settings can be monitored by the “Amp” meter on the
front panel of the welder. Note : Some machines display
“Current” (Same as AMPS) or IMP
• Ideal settings can be found in the wire manufactures data
book for both IPM and Current

21. Shielding Gas
• Air in the welding zone is displaced by inert gas to
“Shield” the molten weld pool and prevent it from
contamination from Oxygen, Nitrogen and Water
present in the atmosphere.
• Insufficient gas flow will not displace the
atmosphere resulting in “porosity” or voids in the
deposited weld.
• Flow is measured in CFH (Cubic Feet per Hour).

22. Insufficient Shielding Gas coverage
• Gas not turned on
• Flow rate not properly adjusted
• Leaks in the hose supplying the shielding
gas to the machine
• GMAW / MIG Gun loose at wire drive
connection
• Spatter buildup on gas cup
• Windy environment