ESAB Multimaster-260, Installation And Operation Manual

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29
hANDLING ThE TorCh
Starting the Arc
There is nothing difficult or technical about starting an are in
the proper manner. We recommend the particular procedure
outlined briefly below, to ensure maximum protection of
the workpiece from the atmosphere at the start of welding
operations.
In a.c. welding, the electrode does not have to touch the
workpiece to start the arc. The superimposed high-frequency
current jumps the gap between the welding electrode and
the workpiece thus establishing a path for the welding cur-
rent to follow. To strike an arc, first turn on the power supply
and hold the torch in a horizontal position about 2 inches
above the workpiece or starting block, as shown in Figure 4-1
below. Then quickly swing the end of the torch down toward
the workpiece, so that the end of the electrode is about 1/8
inch above the plate. The are will then strike.
This downward motion should be made rapidly to provide the
maximum amount of gas protection to the weld zone. Figure
4-2 shows the torch position at the time the arc strikes.
In d.c. welding, the same motion is used for striking an
arc. However, in this case, the electrode must touch the
workpiece in order for the arc to start. As soon as the arc is
struck, withdraw the electrode approximately 1/8 inch above
the workpiece to avoid contaminating the electrode in the
molten puddle. High frequency is usually used to start a d.c.
are. This eliminates the need for touching the workpiece.
The high frequency is automatically turned off by means of
a current relay when the are is started.
The arc can be struck on the workpiece itself or on a heavy
piece of copper or scrap steel, and then carried to the starting
point of the weld. Do not use a carbon block for starting the
arc, as the electrode becomes contaminated causing the arc
to wander (see Section B below). When starting to weld with
a hot electrode, the action must be very rapid as the arc tends
to strike before the torch is in proper welding position.
To stop an arc, merely snap the electrode quickly back up
to the horizontal position. This motion must be made rap-
idly so the arc will not mar or damage the weld surface or
workpiece.
Strongly recommended for proper TIG welding, the use of
hand or foot controls allows the operator to strike the are,
vary welding current and terminate the arc without moving
the torch.
SECTIoN 4 oPErATIoN