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9 GENERAL INFORMATION ON THE WELDING MODES
MMA welding
The manufacturers of the electrodes specify the optimum welding current for
each type of electrode. The type of electrode to be used depends on the
thickness of the material to be welded and on its position.
Insert the chosen electrode into the electrode holder. To strike the electric arc,
rub the electrode against the material to be welded connected to the earth
(ground) clamp. Once the arc is struck, lift the electrode holder slowly to the
normal welding distance.
To strike the arc better, an initial current is supplied which is higher (hot-start)
compared to the welding current. The electrode on melting deposits in the form
of drops onto the piece to be welded and its outer coating is consumed
supplying the shielding gas for the welding. To facilitate the fluidity of the
welding arc, while the drops are coming off, which can cause a short circuit
between the electrode and the weld pool, a momentary increase in the welding
current (arc-force) is given, thus preventing the arc from going out. If the
electrode stays stuck to the piece to be welded, there is an anti-stick function
that, after a certain short-circuit time, cuts off the power to the generator. Thus
you can detach the electrode without damaging it.
When the coating electrodes are used, you need to remove the dross from the
welding after every pass.
TIG welding
In TIG (Tungsten Inert Gas) welding the electric arc is struck between a non-
consumable electrode (pure tungsten or an alloy) and the workpiece in an
atmosphere protected by an inert gas (argon).
The TIG lift-arc process is struck by contact. A low short-circuit welding current
is set to limit the tungsten inclusion on the workpiece. This process does not
guarantee a weld of high quality at the start of the bead.
To completely prevent the tungsten being included, you must not let the
electrode touch the piece to be welded. However you use a start-up with high
frequency (HF) discharge, that allows striking of the electric arc at a distance.
