Chapter 8 Gas Metal and Flux Cored Arc Welding 203 Copyright Goodheart-Willcox Co., Inc. Wire speed control Gas out Contactor cable Manually held gun Work Switch Electrode spool Gas in Flowmeter Shielding gas source Regulator Voltage control Wire feed drive motor Contactor control 24–40V DC supply Welding power source Goodheart-Willcox Publisher Figure 8-11. Diagram of a complete gas metal arc welding (GMAW) outfit. Procedure Preparing a GMAW or FCAW Outfit To prepare a GMAW or FCAW outfit for welding, the follow- ing steps should be taken: 1. Connect a separate wire feed unit to the welding power source, if required. Follow the manufacturer’s instructions to make these connections. Usually, a single cable assembly electrically connects the wire feeder to the welding machine. The welding lead from the positive terminal of the welding machine is usually connected to the wire feeder for GMAW and FCAW–G. Connecting the positive lead to the wire feeder provides DCEP current. For most FCAW–S electrodes, the wire feeder is connected to the negative terminal, which provides DCEN current. 2. Mount the desired welding electrode wire spool onto the wire feeder. See Figure 8-12. 3. Determine what shielding gas is required, if any. See section 8.4.3. Properly secure the cylinder (if used) to prevent it from being knocked over. Check that the regulator and gas flowmeter are attached properly. Connect a hose from the flowmeter to the welding machine or wire feeder as required. The GMAW and FCAW–G processes require a shielding gas connection. The FCAW–S process does not. Finally, the hose and fittings should be checked to make sure there are no leaks in them. 4. Connect the welding gun to the correct place on the welding machine or wire feeder. Quite often, two connections need to be made. Refer to Figure 8-10. Electrode wire spool Retaining ring Drive rolls The Lincoln Electric Company Figure 8-12. A welding wire reel on a wire feeder. One is the main cable that is connected where the welding wire exits the wire feeder. Attach this part of the cable assembly to its proper place. The second connection is for the electrical contact to the gun trigger. This part of the cable assembly also must be connected to its proper place. Confirm all connects are made and are secure. A water-cooled gun has additional connections. Secure the water connections and confirm there are no leaks. (Continued)