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GMAW EQUIPMENT

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WE CAN…

  • IDENTIFY THE BASIC GMAW EQUIPMENT

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  • DESCRIBE FACTORS IN SELECTING GMAW EQUIPMENT

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GMAW ARC WELDING STATION

  • CONSTANT VOLTAGE DC ARC WELDING POWER SOURCE
  • ELECTRODE WIRE FEED MECHANISM
  • ELECTRODE WIRE
  • SHIELDING GAS CYLINDERS
  • SHIELDING GAS
  • GAS REGULATOR
  • SHIELDING GAS FLOWMETER
  • THE ELECTRODE & WORKPIECE LEADS
  • GROUND CLAMP
  • GMAW WELDING GUN

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POWER SOURCES

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GMAW AND FCAW POWER SOURCES

  • GMAW AND FCAW WELDING POWER SOURCES PROVIDE A CONSTANT VOLTAGE

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  • A COMMON TYPE OF POWER SOURCE IS THE TRANSFORMER-RECTIFIER MACHINE

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  • INVERTER POWER SOURCES ARE MUCH SMALLER AND LIGHTER THAN TRADITIONAL TRANSFORMER-RECTIFIER MACHINES

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DIRECT CURRENT

DIRECT CURRENT ELECTRODE NEGATIVE (DCEN):

  • ELECTRODE IS ATTACHED TO THE NEGATIVE POLE
  • WORKPIECE IS ATTACHED TO THE POSITIVE POLE

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DIRECT CURRENT ELECTRODE POSITIVE (DCEP):

  • ELECTRODE IS ATTACHED TO THE POSITIVE POLE
  • WORKPIECE IS ATTACHED TO THE NEGATIVE POLE
  • ALSO CALLED REVERSE POLARITY

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DCEP IS THE PRIMARY METHOD USED IN GMAW

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WELDING GUN

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MIG GUN

  • THE ELECTRODE HOLDER IS COMMONLY REFERRED TO AS THE MIG GUN.

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  • PRIMARY GOAL IS TO DIRECT THE ELECTRODE WIRE

TO THE METAL

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  • CONTAINS THREE PRIMARY PARTS:
    • TRIGGER SWITCH FOR ACTIVATING THE WELDING OPERATION
    • A GAS NOZZLE FOR DIRECTING THE FLOW OF THE SHIELDING GAS
    • A CONTACT TIP

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CONTACT TIP (OR CONTACT TUBE)

  • THIS IS WHERE THE ELECTRICAL CONTACT IS MADE

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  • HELPS TO GUIDE THE WIRE ELECTRODE INTO THE PUDDLE & TRANSMIT THE WELD CURRENT TO THE ELECTRODE WIRE

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  • MUST MATCH THE WIRE DIAMETER (WE USE .035”)

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NOZZLES

  • DIRECTS THE SHIELDING GAS TO THE PUDDLE

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  • THESE ARE SPECIFIC FOR SIZE AND FIT – YOU CANNOT SIMPLY TAKE IT FROM ONE GUN AND PUT IT ON ANOTHER

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GAS DIFFUSER

  • DISTRIBUTING SHIELDING GAS

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INSULATORS

  • PROTECT THE NOZZLE FROM BECOMING ELECTRICALLY HOT

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LINERS

  • PROVIDES A PATH FOR THE ELECTRODE WIRE TO TRAVEL THROUGH THE CABLES
    • PROTECTS THE CABLE FROM CONTINUOUS WEAR

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  • MUST BE COMPATIBLE WITH THE ELECTRODE WIRE DIAMETER

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  • TYPICALLY A COILED STEEL WIRE LINER

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MIG GUN

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WORK OR GROUND CLAMPS

  • MUST HAVE A GOOD CONNECTION TO THE WORK PIECE OR THE METAL TABLE

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  • SHOULD BE INSPECTED BEFORE EACH USE FOR WORN CABLES

GC 500

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ELECTRODE WIRE

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ELECTRODE WIRE

  • ELECTRODE WIRE IS FED THROUGH THE GUN BY A WIRE FEEDER AND CABLE
  • COATED IN COPPER
  • PROVIDED IN LARGE SPOOLS
  • WIRE DEPENDS ON:
    • TYPE OF METAL TO BE WELDED ON
    • JOIN DESIGN
    • SURFACE OF THE METAL
  • WIRE IS MEASURED IN DIAMETER
    • COMMON SIZES INCLUDE: .024, .030, .035, AND .045

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AWS CLASSIFICATION OF ELECTRODES

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ER70S-X

Electrode

Rod

Tensile Strength

Solid

Chemistry, Amount of Deoxidizers

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WIRE FEEDER

  • PULLS ELECTRODE WIRE FROM THE SPOOL AND DRIVES IT THROUGH THE CABLE ASSEMBLY AND GUN AT A CONSTANT RATE OF SPEED

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  • CAN BE CONTAINED INSIDE THE MACHINE OR OUTSIDE OF THE MACHINE

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  • THERE ARE PULL TYPE AND PUSH TYPE DRIVE WHEELS

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  • CORRECT TENSION IS IMPORTANT AND CAN BE ADJUSTED

ON THE DRIVE WHEELS

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  • WIRE FEED SPEED (WFS) CAN BE ADJUSTED
    • MEASURED IN INCHES PER MINUTE (IPM)

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WIRE FEEDERS

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GAS

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SHIELDING GAS

  • DISPLACES THE ATMOSPHERIC AIR WITH A COVER OF PROTECTIVE GAS
  • PROTECTS THE WELD – SIMILAR TO THE FLUX IN SMAW

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ARGON

  • MOST COMMON INERT GAS FOR NONFERROUS METALS
  • VERY STABLE, INERT GAS
  • QUIET AND SMOOTH SOUNDING
  • LITTLE SPATTER
  • CAN BE USED IN AY POSITION
  • COSTS LESS THAN HELIUM
  • DEEP PENETRATION

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HELIUM GAS

  • CONDUCTS HEAT WELL
  • REQUIRES HIGHER ARC VOLTAGE
  • LESS PENETRATION
  • MORE SPATTER
  • MORE EXPENSIVE THAN ARGON

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CARBON DIOXIDE

  • GOOD PENETRATION
  • SPATTER CAN BE A PROBLEM
  • COSTS LESS THAN HELIUM AND ARGON
  • CAN FORM CARBON MONOXIDE
  • USED ONLY ON CARBON STEELS

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GAS MIXTURES

  • ARGON AND CARBON DIOXIDE (C25)

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  • ARGON AND OXYGEN

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  • TRI MIX – HELIUM, ARGON, AND CARBON DIOXIDE

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GAS CYLINDERS

  • THE GAS OF CHOICE IS SUPPLIES IN A COMPRESSED CYLINDER

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  • SAFETY PRACTICES:
    • ALWAYS ROLL ON THE BOTTOM EDGE TO MOVE
    • SAFETY CAP MUST BE ON WHEN NOT IN USE
    • SHOULD BE CHAINED TO A WALL OR CART AT ALL TIMES

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GAUGES AND FLOWMETERS