OPERATION | ||
|
|
|
PULSE WELDING
Pulse welding procedures are set by controlling an overall "arc length" variable. When pulse welding, the arc voltage is highly dependent upon the waveform. The peak current, back ground current, rise time, fall time and pulse frequency all affect the voltage. The exact voltage for a given wire feed speed can only be predicted when all the pulsing waveform parameters are known. Using a preset voltage becomes impracti- cal, and instead the arc length is set by adjusting "trim".
Trim adjusts the arc length and ranges from 0.50 to 1.50, with a nominal value of 1.00. Trim values greater than 1.00 increase the arc length, while values less than 1.00 decrease the arc length.
All pulse welding programs are synergic. As the wire feed speed is adjusted, the Power Wave will automati- cally recalculate the waveform parameters to maintain similar arc properties.
The Power Wave utilizes "adaptive control" to com- pensate for changes in electrical
Arc Control, often referred to as wave control, in pulse programs usually adjusts the focus or shape of the arc. Wave control values greater than 0.0 increase the pulse frequency while decreasing the background cur- rent, resulting in a tight, stiff arc best for high speed sheet metal welding. Wave control values less than
0.0decrease the pulse frequency while increasing the background current, for a soft arc good for
(See Figure B.3)
FIGURE B.3
CURRENT WAVE FORM (PULSE)
Current
Time
PULSE-ON-PULSE™ (GMAW-PP)
Pulse on Pulse™ is a Lincoln process specifically designed for use in welding relatively thin (less than 1/4" thick) aluminum (See Table B.3). It gives weld beads with very consistent uniform ripple.
In Pulse on Pulse modes, two distinct pulse types are used, instead of the single pulse type normally used in
FIGURE B.4
"N" PULSES | "N" PULSES |
HIGH HEAT | LOW HEAT |
PULSES | PULSES |
PEAK |
|
AMPS |
|
BACKGROUND |
|
AMPS |
|
| TIME |
The Peak Current, Background Current, and Frequency are identical for the high energy and low energy pulses. In addition to cooling the weld down, the major effect of the low energy pulses is that they form a weld ripple. Since they occur at very regular time intervals, the weld bead obtained is very uniform with a very consistent ripple pattern. In fact, the bead has its best appearance if no oscillation of the welding gun ("whipping") is used.(See Figure B.5)
FIGURE B.5
When Arc Control is used in the Pulse on Pulse modes, it does the same things it does in the other pulsed modes: decreasing the Arc Control decreases the droplet transfer and weld deposition rate. Increasing the Arc Control increases the droplet trans- fer and weld deposition rate. Since Arc Control varies weld droplet transfer rate, the Arc Control can be used to vary the ripple spacing in the weld bead.