Tweco A80-A120 CutMaster - Manual (Page 21)

CUTMASTER A80, A120
Manual 0-5119 INTRODUCTION
2T-3
A-08331
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 concentra-
tion 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 negative output is connected to the torch elec-
trode through the torch lead. The positive output
is connected to the workpiece via the work cable
and to the torch through a pilot wire.
E. Parts - In - Place (PIP)
The torch includes a 'Parts - In - Place' (PIP) cir-
cuit. When the shield cup is properly installed, it
closes a switch. The torch will not operate if this
switch is open.