Tweco 1000 Merlin(Dec2004) - Manual (Page 43)

Manual 0-2708 4-7 OPERATION
4.06 Cut Quality
Cut quality requirements differ depending on applica-
tion. For instance, nitride build-up and bevel angle may
be major factors when the surface will be welded after
cutting. Dross-free cutting is important when finish cut
quality is desired to avoid a secondary cleaning opera-
tion.
The following cut quality characteristics are illustrated
in Figure 4-7:
Cut Surface
The condition (smooth or rough) of the face of the cut.
Bevel Angle
The angle between the surface of the cut edge and a
plane perpendicular to the surface of the plate. A
perfectly perpendicular cut would result in a 0° bevel
angle.
Top-Edge Rounding
Rounding on the top edge of a cut due to wearing
from the initial contact of the plasma arc on the work-
piece.
Dross Build-up and Top Spatter
Dross is molten material which is not blown out of the cut
area and re-solidifies on the plate. Top spatter is dross
which accumulates on the top surface of the workpiece.
Excessive dross may require secondary clean-up opera-
tions after cutting.
Kerf Width
The width of material removed during the cut.
Nitride Build-up
Nitride deposits which may remain on the cut edge of the
carbon steel when nitrogen is present in the plasma gas
stream. Nitride buildups may create difficulties if the steel
is welded after the cutting process.
Table 4-A Cut Quality on Various Materials
Type of Material
Type of Gases Material Thickness Carbon Steel Stainless Aluminum
Gage Excellent Good - Excellent Good - Excellent
Air Plasma and
Air Secondary
Gage to 1 inch Excellent Good Good
1 to 1-1/2 inches Excellent Good Good
Gage NR Good - Excellent Good - Excellent
Nitrogen Plasma and
Air or CO2 Secondary
Gage to 1/2 inch NR Good - Excellent Good - Excellent
1/2 to 1 inch NR Good - Excellent Good - Excellent
Gage to 1/4 inch NR Good Good
Nitrogen Plasma and
Water Secondary
1/4 to 1/2 inch NR Excellent Good - Excellent
1/2 to 1-1/2 inches NR NR NR
Gage to 1/4 inch NR NR NR
Ar/H2 Plasma and
N2 or CO2 Secondary
1/4 to 1/2 inch NR Good Excellent
1/2 to 1 inch NR Good Good
Oxygen Plasma and
Air Secondary
Gage to 1 inch Excellent NR NR
Oxygen Plasma and
Oxygen Secondary
Gage to 1/4 inch Excellent NR NR