Tweco Maximizer 300 Torch for BNFL - Manual (Page 30)

OPERATION 4-8 Manual 0-2990
E. Lead Angle
The angle between the torch and workpiece depends
on the output current setting and torch travel speed.
At 50 amps, the recommended lead angle is 35°. At a
lead angle greater than 45° the molten metal will not
be blown out of the gouge and may be blown back
onto the torch. If the lead angle is too small (less than
35°), less material may be removed, requiring more
passes. In some applications, such as removing welds
or working with light metal, this may be desirable.
A-00743
35 o
Workpiece
Torch Head
Standoff Height
1/4 - 3/8"
Figure 4-7 Gouging Angle and Standoff Distance
F. Standoff Distance
The tip to work distance affects gouge quality and
depth. A standoff of 1/4 - 3/8 in (6.3 - 9.5 mm) allows
smooth, consistent metal removal. A smaller stand-
off may result in a severance cut rather than a gouge.
A standoff greater than 3/8 in (9.5 mm) may result in
minimal metal removal or loss of transferred main
arc.
G. Slag Build-up
Slag generated by gouging on materials such as car-
bon and stainless steels, nickels, and alloyed steels,
can be removed easily in most cases. Slag does not
obstruct the gouging process if it accumulates to the
side of the gouge path. However, slag build-up can
cause inconsistencies and irregular metal removal if
large amounts of material build up in front of the arc.
The build-up is most often a result of improper travel
speed, lead angle, or standoff height.
Characteristics of Recommended Gases for Plasma Arc Gouging
Type of Gas Type of Material
Plasma Secondary Carbon Steel Stainless Steel Aluminum
Air Air Excellent Good Fair
Nitrogen Air Good Good Fair
Nitrogen CO2 Good Good Good
Ar/H2 Nitrogen Good Excellent (Over 3/4 in) Excellent
Ar/H2 Argon Good Excellent Excellent