Constant Voltage Welding, Pulse Welding

B-4	OPERATION	B-4

CONSTANT VOLTAGE WELDING

Non Synergic CV:

This type of CV mode behaves more like a conventional CV power source. Voltage and WFS are independent adjustments. Therefore to maintain the arc characteristics, the operator must adjust the voltage to compensate for any changes made to the WFS.

All CV Modes:

Arc Control, often referred to as wave control, adjusts the induc- tance of the wave shape. The wave control adjustment is similar to the "pinch" function in that it is inversely proportional to induc- tance. Therefore, increasing wave control greater than 0.0 results in a harsher, colder arc while decreasing the wave con- trol to less than 0.0 provides a softer, hotter arc. (See Figure B.2)

FIGURE B.2

CURRENT WAVE FORM (CV)

Current

Time

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 impractical, 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 automatically recal- culate the waveform parameters to maintain similar arc properties.

The Power Wave utilizes "adaptive control" to compensate for changes in electrical stick-out while welding. (Electrical stick-out is the distance from the contact tip to the work piece.) The Power Wave waveforms are optimized for a 0.75" (19mm) stick-out. The adaptive behavior supports a range of stickouts from 0.50" (13mm) to 1.25" (32mm). At very low or high wire feed speeds, the adaptive range may be less due to reaching physical limitations of the welding process.

Arc Control, often referred to as wave control, in pulse pro- grams usually adjusts the focus or shape of the arc. Wave control values greater than 0.0 increase the pulse frequency while decreasing the background current, resulting in a tight, stiff arc best for high speed sheet metal welding. Wave con- trol values less than 0.0 decrease the pulse frequency while increasing the background current, for a soft arc good for out-of-position welding.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. 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 GMAW-P. A number of high energy pulses are used to obtain spray transfer and transfer metal across the arc. Such pulses are shown in Figure B.4. After a number "N" of such pulses, depending on the wire feed speed used, an identical number "N" of low ener- gy pulses are performed. These low energy pulses, shown in Figure B.4, do not transfer any filler metal across the arc and help to cool the arc and keep the heat input low.

FIGURE B.4

Current	"N" PULSES	"N" PULSES
	HIGH HEAT	LOW HEAT
	PULSES	PULSES
PEAK
AMPS
BACKGROUND
AMPS
		TIME

Lincoln Electric F355I Constant Voltage Welding, Pulse Welding, Pulse-On-Pulse Gmaw-Pp, Current

OPERATION