Effects
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Torch Position
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3 The contact tip-to-work distance, because of its effect on the wire extension, affects the welding current required to melt the wire at a given feed speed. Fig. 7-3 shows the extent to which the welding current requirement can vary with tip-to-work distance. Basically, as the tip-to-work distance is increased, the amount of I2R heating increases and the welding current required to melt the wire is decreased. The converse is also true. Controlling tip-to-work distance is important. Long extensions result in excess weld metal being deposited with low arc heat. This can cause poor bead shape and low penetration. In addition, as the tip-to-work distance increases, the arc becomes less stable. For short arc welding 3/8 in. (9.6mm) tip-to-work distance is recommended. It is very important that the wire extension be kept as constant as possible during the welding operation. In view of the substantial effect on the welding operation, it is always wise to record not only current and voltage, but also the wire-feed speed. Figure 7-3 – Effect of Tip-To-Work Distance on Welding Current