Method and apparatus for automatic gas control for a plasma arc torch

A plasma arc torch for cutting a workpiece, the plasma arc torch having a plasma gas source to supply a plasma chamber, such that an electrical current passing between an electrode and a nozzle produces a plasma arc that exits the plasma arc torch through a nozzle exit orifice, the plasma arc torch comprising:

• a means for sensing a parameter in a first fluid line that supplies a plasma gas from the plasma gas source;
• and
• a means for controlling a flow of the plasma gas based on the sensed parameter using a programmable control valve disposed in the first fluid line of the plasma arc torch, the programmable control valve using a predetermined setpoint curve to prolong electrode life or to optimize a duty cycle based on associating the flow with a duration of an operation of the electrode producing the plasma arc by:
• (a) increasing the plasma gas ramp down time for a longer duration electrode operation or (b) decreasing the plasma gas ramp down time for a shorter duration electrode operation.

A method for control of a plasma gas flow to a plasma arc torch for prolonging a life of an electrode or optimizing a duty cycle, the plasma arc torch including a plasma chamber defined by the electrode and a nozzle and disposed within a body of the plasma arc torch, the method comprising the steps of:

• providing a first fluid line for supplying a plasma gas to the plasma chamber;
• positioning in the first fluid line of the plasma arc torch a programmable control valve using a predetermined setpoint curve to control a flow of the plasma gas;
• and
• controlling the flow of the plasma gas to the plasma chamber during shutdown of the torch, the controlling comprising:
• (i) increasing, by manipulating the programmable control valve via a digital signal processor, a ramp down time of the flow of the plasma gas to the plasma chamber when the plasma arc torch has been operated for a duration of an operation of the electrode at a higher current level or (ii) decreasing, by manipulating the programmable control valve via the digital signal processor, the ramp down time of the flow ofthe plasma gas to the plasma chamber when the plasma arc torch has been operated for a duration of an operation of the electrode at a reduced current level.

A plasma arc torch for cutting a workpiece, the plasma arc torch having a plasma gas source to supply a plasma chamber, such that an electrical current passing between an electrode and a nozzle produces a plasma arc that exits the plasma arc torch through a nozzle exit orifice, the plasma arc torch comprising:

• a means for sensing a parameter in a first fluid line that supplies a plasma gas from the plasma gas source;
• and
• a means for controlling a flow of the plasma gas based on the sensed parameter using a programmable control valve disposed in the first fluid line of the plasma torch, the programmable control valve using a predetermined setpoint curve to prolong electrode life or to optimize a duty cycle by:
• (a) increasing the first gas ramp down time when the plasma arc torch has been operated for a duration of an operation of the electrode at a higher current level, or (b) decreasing the first gas ramp down time when the plasma arc torch has been operated for a duration of an operation of the electrode at a reduced current level.