204 Modern Welding Copyright Goodheart-Willcox Co., Inc. Warning When setting up the GMAW or FCAW station, look for all potential safety problems. Spatter from GMAW or FCAW can cause a fire. All flammable materials must be removed from the welding area. 8.4.1 Setting Up a GMAW/FCAW Power Source In order to produce acceptable welds, a GMAW/ FCAW power source must be properly adjusted for the material being joined and the desired metal transfer method. Before setting up the power source, the fol- lowing information must be known: • The type of base metal to be welded. • Base metal thickness. • The type and diameter of welding wire. • The type of transfer method to be used. • The type of shielding gas to be used. Once this information is known, the welding machine can be properly set up. Only a few controls must be set prior to welding. See Figure 8-13. First, adjust the voltage setting. The voltage deter- mines the arc length and helps determine the metal transfer method. Other factors also affect the transfer method, as discussed in sections 8.2.1 through 8.2.4. Second, adjust the wire feed speed. When the wire feed speed is adjusted, the machine’s welding amper- age is also adjusted. Figure 8-14 through Figure 8-22 list the voltage and amperage settings for welding different base metals using both short circuiting transfer and spray transfer. 5. Connect the workpiece lead to the welding machine. Both the welding gun cable assembly and the workpiece lead should be checked for any signs of wear or cuts. Wear or cuts on the outside of these items may indicate damage to the leads. 6. The workpiece clamp should be checked. The clamp should be clean so it can make a good electrical connection. 7. If a water cooler is used, connect it to the welding machine or to the gun according to the manufacturers’ recommendations. The welding machine, wire feeder, or welding gun is connected to the outlet on the water cooler. This way, cool water flows from the cooler to the gun. Warm water returning from the gun is connected to the inlet on the water cooler. GMAW Spray Transfer — Carbon Steel Electrode diameter Arc voltage Amperage range inches mm V A 0.030 0.035 0.045 1/16 3/32 0.8 0.9 1.2 1.6 2.4 24–28 24–28 24–30 24–32 24–33 150–265 175–290 200–315 275–500 350–600 Note: The values shown are based on the use of argon with 2%–5% oxygen for mild and low-alloy steel. Goodheart-Willcox Publisher Figure 8-15. Approximate machine settings for spray transfer on carbon or low-alloy steel. GMAW Short Circuit Transfer — Carbon Steel Electrode diameter Arc voltage Amperage range inches mm V A 0.030 0.035 0.045 0.8 0.9 1.2 15–21 16–22 17–22 70–130 80–190 100–225 Note: The values shown are based on the use of CO 2 for mild steel and argon CO2 for low-alloy steel. Goodheart-Willcox Publisher Figure 8-14. Approximate machine settings for short circuiting metal transfer on carbon and low-alloy steel. Gun cable connection Gun trigger connection Voltage adjustment Wire feed adjustment Jog switch Purge switch Voltage and current meters Power on/off Miller Electric Mfg. Co. Figure 8-13. A GMAW/FCAW power source.