Control Panel and Power Source.--The control
The electrode must be concentric with the
panel is the operating station for the machine. It
electrode outside diameter.
controls the power supply to the torch. The power
supply is a 200-volt, open-circuit, dc power source with
A scribe line on the electrode body indicates
a drooping volt/ampere characteristic. It also provides
the limit to which the electrode can be
a pilot power supply of less than 200 volts, dc, open
circuit for the operation of the pilot arc to start the arc
cutting process. A typical control panel will have a gas
Torch Leads.--The plasma arc machine has four
flowmeter, ammeter, fuse panel, gas mixing control
different color-coded torch leads and connections to
supply plasma gas and cooling water to the torch. The
panel, and amperage setting dial.
four color-coded connections are as follows:
Plasma Arc Torch.--The torch body is composed
of a handle, a ceramic cup, and a tungsten electrode.
Green for the negative water-cooled lead
The handle is similar to a GTAW torch and serves as an
attachment base for the ceramic cup and as an electrode
Red for the positive water-cooled lead
holder. The ceramic cup concentrates and columnates
the energy of the arc stream created inside the torch.
The electrode provides the electrical current required to
Black for the plasma gas
produce the ionized plasma gas. The electrode should
be replaced if it becomes eroded or out-of-round.
Yellow for the shield gas
Resharpen the electrode when the eroded part in the
CAUTION: Purge the gas hoses prior to use to
center becomes l/8 inch in diameter. Keep the
remove any moisture that may have entered the torch or
following points in mind when sharpening electrodes:
leads during storage, shipment, or setup.
Sharpen the electrode with a 0.218-inch
Gas Mixture.--Gas mixtures for plasma arc
diameter, flat in the center, and a 60-degree
cutting serves similar functions as those used for GTAW
welding. A mixture of argon (AR) and hydrogen (H)
Figure 13-37.--Plasma arc cutting equipment.