Lincoln Electric 405M, 355M service manual Pulse Welding GMAW-P, Figure B.3

B-8 OPERATION B-8

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SPECIAL WELDING PROCESSES AVAILABLE ON THIS MACHINE

PULSE WELDING (GMAW-P)

The pulsed-arc process is, by definition, a spray trans- fer process wherein spray transfer occurs in pulses at regularly spaced intervals. In the time between pulses, the welding current is reduced and no metal transfer occurs.

Pulsed-arc transfer is obtained by operating a power source between low and high current levels. The high current level or “pulse” forces an electrode drop to the workpiece. The low current level or “background” main- tains the arc between pulses. (See Figure B.3).

Pulsed MIG is an advanced form of welding that takes the best of all the other forms of transfer while mini- mizing or eliminating their disadvantages. Unlike short circuit, pulsed MIG does not create spatter or run the risk of cold lapping. The welding positions in pulsed MIG are not limited as they are with globular or spray and its wire use is definitely more efficient. Unlike the spray arc process, pulsing offers controlled heat input that allows better welding on thin materials. Pulsing allows for lower wire feed speeds which leads to less distortion and improved overall quality and appear- ance. This is especially important with stainless, nick- el and other alloys that are sensitive to heat input.

In GMAW-P mode, arc control adjusts the background current and frequency of the wave. When arc control goes up, the frequency increases thus increasing the droplet transfer.

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FIGURE B.3

EACH PULSE DELIVERS ONE DROPLET OF WELD MATERIAL

PEAK AMPS

FREQUENCY

SPRAY TRANSITION

CURRENT

POWER WAVE 355M/405M