Tweco CutMaster 12mm - Manual (Page 20)

CUTMASTER 12mm
2T-2 INTRODUCTION Manual 0-5076
G. Gas Requirements
Manual and Mechanized Torch Gas Specifications
Gas (Plasma and Secondary) Compressed Air
Operating Pressure
Refer to NOTE
60 - 95 psi
4.1 - 6.5 bar
Maximum Input Pressure 125 psi / 8.6 bar
Gas Flow (Cutting and Gouging)
300 - 500 scfh
142 - 235 lpm
!
WARNING
This torch is not to be used with oxygen (O
2
).
NOTE
Operating pressure varies with torch model, op-
erating amperage, and torch leads length. Refer
to gas pressure settings charts for each model.
H. Direct Contact Hazard
For standoff tip the recommended standoff is 3/16 inches
/ 4.7 mm.
2T.04 Options And Accessories
For options and accessories, see section 6.
2T.05 Introduction to Plasma
A. Plasma Gas Flow
Plasma is a gas which has been heated to an extremely
high temperature and ionized so that it becomes electri-
cally conductive. The plasma arc cutting and gouging
processes use this plasma to transfer an electrical arc to
the workpiece. The metal to be cut or removed is melted
by the heat of the arc and then blown away.
While the goal of plasma arc cutting is separation of the
material, plasma arc gouging is used to remove metals to
a controlled depth and width.
In a Plasma Cutting Torch a cool gas enters Zone B, where
a pilot arc between the electrode and the torch tip heats and
ionizes the gas. The main cutting arc then transfers to the
workpiece through the column of plasma gas in Zone C.
A-00002
Workpiece
Power
Supply
+
_
C
B
A
Typical Torch Head Detail
By forcing the plasma gas and electric arc through a small
orifice, the torch delivers a high concentration of heat to a
small area. The stiff, constricted plasma arc is shown in
Zone C. Direct current (DC) straight polarity is used for
plasma cutting, as shown in the illustration.
Zone A channels a secondary gas that cools the torch. This
gas also assists the high velocity plasma gas in blowing
the molten metal out of the cut allowing for a fast, slag -
free cut.
B. Gas Distribution
The single gas used is internally split into plasma and
secondary gases.
The plasma gas flows into the torch through the negative
lead, through the starter cartridge, around the electrode,
and out through the tip orifice.
The secondary gas flows down around the outside of the
torch starter cartridge, and out between the tip and shield
cup around the plasma arc.
C. Pilot Arc
When the torch is started a pilot arc is established between
the electrode and cutting tip. This pilot arc creates a path
for the main arc to transfer to the work.
D. Main Cutting Arc
DC power is also used for the main cutting arc. The nega-
tive output is connected to the torch electrode through
the torch lead. The positive output is connected to the
workpiece via the work cable and to the torch through a
pilot wire.