Lincoln Electric IM520-B manual Welding Operation, Hand and Foot Amptrol Accessory Operation

OPERATION

HAND AND FOOT AMPTROL ACCESSORY OPERATION

Both the Hand and Foot Amptrol work in a similar manner. They are meant to be used for remote current control when Remote Current Control is selected. The TIG 2-Step mode must be selected when using an Amptrol for remote current control. As explained below, Amptrols can also be used as arc start switches if Local Current Control is selected.

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” position, as it would be with no foot pressure, or a Hand Amptrol in the relaxed position, with no thumb pressure. “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 displayed on the ammeter. For example, if the ammeter is preset for 200 amps and the Current Control switch is in the REMOTE position, the Amptrol, when depressed just past its minimum position, will cause the Square Wave TIG 255 to weld at 5 amps. At the Amptrols maximum position, the output would be near 200 amps.

It is important to note that, for many applications, the tungsten will not start an arc at only 5 amps. 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 approximately 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.

If the Current Control switch is set to the LOCAL position, an Amptrol can be used as an arc start switch. Depressing the Amptrol just past minimum will cause the Amptrols built-in arc start switch to close, and backing off completely causes the built-in start switch to open. The Amptrol will have no effect on the welding current when used as an arc start switch.

WELDING OPERATION

TIG Welding

Familiarize yourself with the Controls and Display Section before attempting operation of the Square Wave TIG 255.

TIG Welding Guidelines

TIG welding can be done in either the TIG 2-Step or the TIG 4-Step Weld Mode. TIG 2-Step is typically used with Hand or Foot Amptrols, with Remote Current control. TIG 4-Step is typically used with Arc Start switches and Local Current Control, because it provides a very brief current upslope, and a 5-second current downslope. TIG 4-Step also functions like a trigger interlock, making it unnecessary to hold down the Arc Start switch during a weld. Note, on later versions, TIG 4-Step was made available for use with Remote Current Control with the release of ROM version S21228-4 (initiated on Control board G2150-3 on codes 10022 and higher). This feature requires that the remote control devise in use must have separate Arc Start and Output Control mechanisms. Read the TIG Welding Sequence of Operation sections for more details on 2-Step and 4-Step Operation.

TABLE 2

RECOMMENDED POLARITY

SETTINGS FOR TIG WELDING

	Electrode	High Frequency
Type of Welding	Polarity	Setting
Stainless Steel	DC-	START
Aluminum & Magnesium	AC	CONTINUOUS
Other Metals	DC-	START

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