Plasma arc torch and cutting system

A plasma arc torch, comprising:

• a nozzle body;
• a nozzle extending from the nozzle body;
• a shield cap;
• an outer retaining cap attached to the plasma arc torch that secures the shield cap to the plasma arc torch;
• a sleeve located radially outward from the outer retaining cap and configured to receive a flow of pressurized gas;
• an insulator located between the outer retaining cap and the sleeve;
• and
• a shield extending from the sleeve axially past a distal terminal end of the outer retaining cap, wherein at least one of the sleeve and the insulator forms a gas flow channel configured to direct a gas flow from the sleeve to a distal portion of the outer retaining cap, and wherein the shield is radially offset from the outer retaining cap and the shield cap so as to form an air gap between the shield and both of the outer retaining cap and the shield cap for conducting the gas flow to a distal terminal end of the plasma arc torch.

A plasma cutting system, comprising:

• a plasma arc torch;
• a plasma cutting power supply that supplies a plasma cutting current to the plasma arc torch;
• a torch actuator that moves the plasma arc torch during a cutting operation;
• a motion controller operatively connected to the torch actuator to control movements of the plasma arc torch during the cutting operation;
• and
• a gas controller configured to control a flow of plasma gas and a flow molten metal clearing gas to the plasma arc torch,
• wherein the flow of molten metal clearing gas is active during a piercing operation of the plasma arc torch, and the gas controller is configured to automatically determine a completion of the piercing operation and stop the flow of molten metal clearing gas upon determining the completion of the piercing operation.

An attachment for a plasma arc torch, comprising:

• an outer retaining cap that is attachable to the plasma arc torch and that is configured to secure a shield cap to the plasma arc torch;
• a sleeve located radially outward from the outer retaining cap and configured to receive a flow of pressurized gas;
• an insulator located between the outer retaining cap and the sleeve;
• and
• a gas flow channel configured to direct a gas flow from the sleeve to a distal portion of the outer retaining cap, wherein the gas flow channel comprises a plurality of grooves arrayed annularly around an outer surface of the insulator and wherein the sleeve includes an annular plenum, and the plurality of grooves extend axially from the annular plenum to a distal terminal end of the insulator.

An attachment for a plasma arc torch, comprising:

• an outer retaining cap that is attachable to the plasma arc torch and that is configured to secure a shield cap to the plasma arc torch;
• a sleeve located radially outward from the outer retaining cap and configured to receive a flow of pressurized gas;
• an insulator located between the outer retaining cap and the sleeve;
• a gas flow channel configured to direct a gas flow from the sleeve to a distal portion of the outer retaining cap;
• and
• a shield extending from the sleeve axially past a distal terminal end of the outer retaining cap, wherein the shield is radially offset from the outer retaining cap so as to form an air gap between the shield and the outer retaining cap for conducting the gas flow to a distal terminal end of the plasma arc torch.

A plasma cutting method, comprising the steps of:

• providing an open air plasma cutting system for cutting a workpiece in open air, wherein the open air plasma cutting system includes a plasma arc torch;
• initiating a flow of plasma gas to the plasma arc torch;
• initiating a flow of molten metal clearing gas to the plasma arc torch;
• and
• automatically stopping the flow of molten metal clearing gas to the plasma arc torch upon determining a completion of a piercing operation while controlling the flow of plasma gas to the plasma arc torch.