Lincoln Electric SVM141-A Advanced TIG Welding Features, Hand and Foot Amptrol Operation

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OPERATION

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11.Hold the Arc Start Switch down until an arc is established. The arc will start at a low current value that is equal to 25% of the preset current established in Step 4. It will remain at this current as long as the Arc Start Switch is closed. Release the Arc Start Switch. At this point, the Square Wave TIG 275 will quickly ramp up to the preset maximum welding current, (0.5 seconds upslope time) and the weld will continue indefinitely. Press the Arc Start Switch a second time to initiate the Downslope time. The current will go down to a crater fill current that is equal to 25% of the weld- ing current. Release the Arc Start Switch to stop the arc and start the Post flow timer. After the Post flow time has expired, the gas and optional water valves will close. To make another weld, repeat steps 10 and 11.

HAND AND FOOT AMPTROL OPERATION

Both the Hand and Foot Amptrol work in a similar man- ner. They are meant to be used for remote current con- trol. The TIG 2-Step mode must be selected when using an Amptrol for remote current control.

For simplicity, the following explanation will refer only to "Amptrols", meaning both Foot and Hand models. The term "minimum" refers to a Foot pedal in the "up" posi- tion, as it would be with no foot pressure, or a Hand Amptrol in the relaxed position, with no thumb pres- sure. "Maximum" refers to a fully depressed Foot Amptrol, or a fully extended Hand Amptrol.

The Amptrol is capable of controlling the output current from 5 amps to the preset current on the output control knob. For example, if the preset is at 200 amps, the Amptrol, when depressed just past its minimum posi- tion, will cause the Square Wave TIG 275 to weld at 5 amps. At the Amptrol's maximum position, the output will be near 200 amps.

It is important to note that, for many applications, the tungsten will not start an arc at only 5 amps. (Refer to the TIG Welding Guidelines for recommended tungsten currents.) To start an arc reliably, it is important to depress the Amptrol far enough so that the machine output current is near the tungsten operating range. In the example above, a 3/32" tungsten may be used on DC- to weld near 200 amps. To start the weld, the operator may have to depress the Amptrol approxi- mately 1/4 of the way down, or to nearly 50 amps, in order to start the arc. Merely depressing the Amptrol to its 5 amp minimum position will not start the arc.

ADVANCED TIG WELDING FEATURES

AC WAVE BALANCE AND AUTO BALANCE™

The AC Wave Balance feature is unique to the Square Wave TIG 275. It is active only in AC TIG mode. It con- trols the amount of positive and negative current in the AC output.

The Square Wave TIG 275 allows the operator to select Auto Balance™. This selection provides auto- matic adjustment of the AC Wave Balance; it is suitable for most welding conditions. Auto Balance™ gives the ideal amount of cleaning and penetration, based on the welding current output.

Manual adjustment of the AC Wave Balance is also possible. Manual Balance settings vary from 0 (maxi- mum cleaning) to 10 (maximum penetration). A setting of 3 yields a balanced output (equal amounts of clean- ing and penetration). Use the following as a guide when setting the Balance manually:

BALANCED (3): The amounts of positive and negative are the same.

CLEANING (0 to 2): Provides more positive current than negative current. Since the positive cur- rent produces the "cleaning" or oxide removal on aluminum, this setting is used for welding on heavily oxidized aluminum.

PENETRATION (4 to 10): Provides more negative cur- rent than positive. The arc plasma will be more concentrated and more easily directed to where the heat is needed. Higher penetration settings allow a given size of tungsten to carry more cur- rent.

CAUTION: Use only the amount of cleaning required because the greater amount of positive current will heat the tungsten more and possibly cause it to melt or "spit". Also, the arc is usually more flared and less sta- ble with more cleaning current.

In general, use just enough "cleaning" to remove oxides and to give good wetting of the puddle.

SQUARE WAVE TIG 275