Arc Welding/Cutting Equipment
Gas Metal Arc Welding (GMAW / MIG)
Gas metal arc welding utilizes a continuously fed consumable wire electrode shielded by inert or semi-inert gas, enabling efficient welding of various metals with high productivity and minimal cleanup.
What is MIG Welding?
Equipment includes: DC power source, wire feeder, MIG torch, shielding gas, regulator, wire spool, helmet, and PPE.
Operation Steps: The following is a brief list of steps to safely operate the equipment:
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Inspect Equipment
- Check the welder, cables, gun, and shielding gas supply for damage or leaks.
- Ensure proper wire type and size is loaded in the machine.
- Confirm all connections are secure.
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Set Up Gas Supply
- Secure the gas cylinder and open the valve slowly.
- Adjust the flow rate (typically 20–30 CFH for most MIG welding).
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Adjust Machine Settings
- Select appropriate voltage and wire feed speed for material thickness and type.
- Consult a settings chart or welding procedure specification (WPS) if available.
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Prepare the Workpiece
- Clean the metal surface to remove rust, paint, oil, or other contaminants.
- Clamp the workpiece securely and connect the ground clamp to clean metal.
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Start Welding
- Position the welding gun at the correct angle and distance from the workpiece.
- Pull the trigger to start the arc and feed wire.
- Maintain a steady travel speed and motion to create a quality weld.
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Shut Down
- Release the trigger to stop welding.
- Close the shielding gas valve.
- Turn off the welding machine.
- Inspect the weld for quality and safety.
Safe Operation Guidelines: The following safe procedures and practices help prevent welding injuries and illnesses:
- Verify correct shielding gas and flow rates are being used to ensure weld quality and to prevent contamination from surrounding air.
- Inspect wire feeder, welding gun, cables, and grounding clamp. Damaged or worn-out equipment can cause electrical hazards, inconsistent wire feeding, and poor arc stability.
- Always wear an auto-darkening helmet to shield the welder from UV radiation, sparks, spatter, and heat.
- Wear welding gloves to prevent burns, and protective clothing to reduce skin exposure to hot metal and radiation.
- Maintain a safe distance from welding fumes, or use extraction equipment. Keeping distance or using fume extraction prevents inhalation of harmful particles and gases, which can cause respiratory issues or long-term health problems.
- Check the welding gun regularly for spatter build-up. Spatter can clog the nozzle or contact tip, leading to poor wire feeding, inconsistent arcs, and potential overheating.
- Shut off the gas cylinder valve after the welding session. Leaving the gas cylinder open can result in leaks, wasting shielding gas and creating a fire or explosion hazard.
- Regularly inspect and clean drive rollers and gun liners. Dirt or debris in the drive system can cause erratic wire feeding or damage to the wire.
An employee was on an aerial lift, welding connections on beams at a building under construction. He was holding the 220V welding feeder in his right hand and removing slag with his left hand using a metal scraper. As the feeder in his right hand was feeding wire out of the tip, it curled toward his arm and contacted his jacket, which was saturated with water and sweat. The worker then received an electric shock. He was found unconscious with his arm on fire. The employee was hospitalized for treatment.
Knowledge Check Choose the best answer for the question.
4-5. What is the purpose of verifying the correct shielding gas and flow rates during welding?
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