Page 46 - Welding Robots Technology, System Issues, and Applications
P. 46
Welding Technology
31
2.1.2.5 Shielding Gas Regulator
The regulator is a device that reduces source gas pressure to a constant working
pressure, independently of source pressure variations. Pressure reduction can be
made in one or two stages. Regulators in two stages give in general more stable
output flow.
2.1.3 Process Parameters
In this section the relevant parameters for the GTAW process will be reviewed
with the double objective of presenting them and showing that they can certainly
be used for automatic robotic welding.
2.1.3.1 Current
Current has direct influence on weld bead shape, on welding speed and quality of
the weld. Most GTAW welds employ direct current on electrode negative (DCEN)
(straight polarity) because it produces higher weld penetration depth and higher
travel speed than on electrode positive (DCEP) (reverse polarity). Besides, reverse
polarity produces rapid heating and degradation of the electrode tip, because anode
is more heated than cathode in gas tungsten electric arc.
DCEP
AC
DCEN
Figure 2.5. Effect of current and polarity on weld bead shape
