PRO-POINT 9085986 Mode D'emploi page 33

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grain' (Fig. 21). If electrodes are ground crosswise, the electrons have to jump
across the grinding marks and the arc can start before the tip and wander.
Grinding longitudinally with the grain, the electrons flow steadily and easily
to the end of the tungsten tip. The arc starts straight and remains narrow,
concentrated and stable.
ELECTRODE TIP/FLAT
The shape of the tungsten electrode tip is an important process variable in
precision arc welding. A good selection of tip/flat size will balance the need
for several advantages. The bigger the flat, the more likely arc wander will
occur and the more difficult it will be to arc start. However, increasing the flat
to the maximum level that still allows arc start and eliminates arc wander will
improve the weld penetration and increase
the electrode life (Fig. 22). Some welders
still grind electrodes to a sharp point,
which makes arc starting easier. However,
they risk decreased welding performance
from melting at the tip and the possibility
of the point falling off into the weld pool.
ELECTRODE INCLUDED ANGLE/TAPER - DC WELDING
Tungsten electrodes for DC welding should be ground longitudinally and
concentrically with diamond wheels to a specific included angle in conjunction
with the tip/flat preparation. Different angles
produce different arc shapes and offer
different weld penetration capabilities
(Fig. 23). In general, blunter electrodes that
have a larger included angle provide the
following benefits:
• Last Longer.
• Have better weld penetration.
• Have a narrower arc shape.
• Can handle more amperage without eroding.
Sharper electrodes with smaller included angle provide:
• Offer less arc weld.
• Have a wider arc.
• Have a more consistent arc.
The included angle determines weld bead shape and size. Generally, as the
included angle increases, penetration increases and bead width decreases.
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AC/DC Inverter TIG/Arc Welder 9085986
Fig. 22
Fig. 23
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