220 Modern Welding Copyright Goodheart-Willcox Co., Inc. An increased electrode extension distance preheats the electrode wire. If the electrode extension is not suffi cient, the electrode wire will not be preheated enough. Figure 8-44 lists proper electrode extensions for GMAW and FCAW processes. A long extension may cause too much fi ller metal to be deposited with low heating by the arc. This may cause shallow penetration and a high-crowned weld bead shape. In spray transfer, if the extension is too short, proper preheating of the welding wire does not occur. In FCAW–S, the proper electrode extension is important. If the welding wire is not properly pre- heated, the fl ux will not produce the shielding gas necessary to protect the welding area. 8.7 Welding Techniques Most arc welding processes require the welder to con- trol the arc length, welding speed, gun angle, and gun motions to obtain a good weld. In GMAW and FCAW, the arc length remains constant and is determined by the arc voltage set on the welding machine. While gas metal or fl ux cored arc welding, the welder must watch and control the distance from the nozzle or con- tact tip to the work. Refer to Figure 8-43. By control- ling the nozzle-to-work distance, the welder controls the electrode extension distance. The welding speed affects the bead width and pen- etration. A slower weld speed produces a wider bead and deeper penetration. Gun angle also affects the bead width and penetration. The welder can use weave motions and change the gun angle as needed to obtain the desired weld pool. The terms forehand, backhand, and perpendicular are used to describe the angles at which the gun can be held in relation to the weld bead. In forehand welding, the tip of the electrode points in the direction of travel. This is often referred to as a push angle or push travel angle. In backhand welding, the electrode tip points away from the direction of travel. This is often called a drag travel angle. Perpen- dicular welding is done with the electrode at a 90° angle to the base metal. This is a travel angle of zero. Figure 8-45 shows the effects of these various angles. GMAW and FCAW Electrode Extensions Process Method Electrode extension GMAW Short circuiting 1/4″–1/2″ (6 mm–13 mm) GMAW Spray transfer 1/2″–1″ (13 mm–25 mm) FCAW Gas-shielding 3/4″–1 1/2″ (19 mm–38 mm) FCAW Self-shielding 3/4″–3 3/4″ (19 mm–95 mm) Goodheart-Willcox Publisher Figure 8-44. Recommended electrode extension distances for GMAW and FCAW. Forehand Perpendicular Backhand 25° drag travel angle 25° push travel angle Direction of travel Direction of travel Direction of travel Goodheart-Willcox Publisher Figure 8-45. Effects of the welding gun angle on the bead. Notice that the backhand angle gives the deepest penetration.