Tweco XTTM-301 - Manual (Page 51)

Manual 0-4768 4-13 OPERATION
E. Dross
When dross is present on carbon steel, it is commonly
referred to as either “high speed, slow speed, or top
dross”. Dross present on top of the plate is normally
caused by too great a torch to plate distance. "Top
dross" is normally very easy to remove and can often
be wiped off with a welding glove. "Slow speed dross"
is normally present on the bottom edge of the plate. It
can vary from a light to heavy bead, but does not ad-
here tightly to the cut edge, and can be easily scraped
off. "High speed dross" usually forms a narrow bead
along the bottom of the cut edge and is very difficult to
remove. When cutting a troublesome steel, it is some-
times useful to reduce the cutting speed to produce
"slow speed dross". Any resultant cleanup can be
accomplished by scraping, not grinding.
4.07 Torch Operation
A. Cutting With Torch
1. Use a square to check that the torch is perpendicu-
lar to the workpiece to obtain a clean, vertical cut.
Rack and
Pinion Mounting
Assembly
Square
A-00660
Workpiece
Checking Alignment
2. To start a cut at the plate edge, position the center
of the torch along the edge of the plate.
3. The torch can be activated by the remote operator
control panel, remote control pendant, or by re-
mote interface device such as CNC. After a two
second gas purge, the pilot arc will start. The pilot
arc will stay on as long as the torch is activated or
until main arc starts.
4. With the pilot arc on, the main cutting arc will
be established when the torch is brought within
1/16 - 1/4 in (1.6 - 6.4 mm) of the workpiece. If
the cutting arc is interrupted and the torch is
still activated, as when cutting expanded metal,
the pilot arc will automatically restart (see
NOTE). Deactivating the torch will shut off ei-
ther the pilot or main arc, depending on the mode
of operation.
NOTE
Refer to High/Low Speed Auto-Restart Function in
the Plasma Power Supply Operating Manual.
5. Cut with a standoff of 1/16 - 1/4 in (1.6 - 6.4 mm)
from the work. The torch should be held perpen-
dicular to the workpiece while cutting. Start cut-
ting slowly and adjust cutting speed for optimum
cutting performance. Refer to the Appendix pages
for typical cutting speeds for various materials and
material thicknesses.