Gas flow control for a plasma arc torch is provided. More particularly, a method and apparatus to modulate the pressure and flow from a plasma arc torch is provided. Cyclic pulsing of a flow control valve between states of fully open and fully closed provides for a relatively constant flow of plasma gas to the torch at a relatively constant pressure.

An electrode is provided for use in a plasma arc torch. The electrode includes a body having an elongated forward portion and a ring-shaped aft portion. The forward portion is configured to provide an electrically conductive path from the distal end to the proximal end. The forward portion comprises a first conductive material. The ring-shaped aft portion, defining a hollow center, is configured to substantially surround a portion of the forward portion when the forward portion is located inside of the hollow center. The aft portion includes a pneumatic reaction region for receiving a biasing flow of a pressurized gas. The aft portion comprises a second material. In some embodiments, the first conductive material is the same as the second material.

Gas flow control for a plasma arc torch is provided. More particularly, a method and apparatus to modulate the pressure and flow from a plasma arc torch is provided. Cyclic pulsing of a flow control valve between states of fully open and fully closed provides for a relatively constant flow of plasma gas to the torch at a relatively constant pressure.

A method of operating a plasma arc torch system is provided. A first plasma gas supply source, a second plasma gas supply source, and a control unit are provided. A first plasma gas composition is flowed through a first plasma gas flow path, and a plasma arc is generated using the first plasma gas composition. After arc generation, the plasma gas composition is changed to a second plasma gas composition, and the plasma gas flow path is changed to a second plasma gas flow path, wherein the second plasma gas flow path is different from the first plasma gas flow path. The plasma arc is sustained using the second plasma gas composition. The first and second plasma gas flow paths are both at least partially disposed within the plasma arc torch.

In some aspects, methods for preserving a usable life of a plasma arc electrode consumable installed in a plasma arc torch can include measuring a characteristic of an electrical signal being provided to the torch to generate a plasma arc between the torch and a workpiece to be processed; monitoring the characteristic during operation of the torch over a time period; comparing the characteristic to a threshold value; and, responsive to determining that a measured characteristic meets and/or exceeds the threshold value, initiating an arc extinguishing sequence to preserve the life of the electrode.

In some aspects, methods for limiting damage to a plasma arc torch body resulting from a consumable failure within the torch can include determining a specified conductivity parameter set point of a current to be provided to the plasma arc torch for a material processing operation; measuring a detected conductivity parameter of plasma arc current being provided to the plasma torch to perform the material processing operation; comparing the specified conductivity parameter set point to the detected conductivity parameter of plasma arc current and calculating an error term signal; and based on a determination that the error term signal exceeds a threshold amount, initiating a plasma arc shut down sequence to extinguish the plasma arc to limit damage to the plasma arc torch body.

In some aspects, methods of initiating a plasma arc of a plasma arc torch to pierce a workpiece and detecting plasma piercing through the workpiece to begin a cutting sequence can include calculating a pulse width modulation characteristic of an electrical signal associated with a plasma arc between an electrode of a plasma arc torch and a workpiece to be processed; monitoring the characteristic during operation of the torch over a time period of a workpiece piercing sequence; comparing the characteristic to a threshold value; and responsive to determining that a calculated characteristic meets and/or exceeds the threshold value, ending the workpiece piercing sequence and beginning the cutting sequence and causing the plasma arc torch to move relative to the workpiece to form a cut.

An apparatus is disclosed wherein an electric arc is employed to heat an injected gas to a very high temperature. The apparatus comprises four internal components: a button cathode and three cylindrical co-axial components, a first short pilot insert, a second long insert and an anode. Vortex generators are located between these components for generating a vortex flow in the gas injected in the apparatus and which is to be heated at very high temperature by the electric arc struck between the anode and cathode. Cooling is provided to prevent melting of three of the internal components, i.e. the cathode, the anode and the pilot insert. However, to limit the heat loss to the cooling fluid, the long insert is made of an insulating material. In this way, more electrical energy is transferred to the gas.

Known plasma cutting machines comprise a plasma burner that can be moved by means of a movement unit, a distance sensor that can be actuated at a low voltage level and has an electronic control unit for determining the distance between a workpiece to be machined and said plasma burner, an ignition device which can be actuated at a high voltage level and by means of which an ignition process can be triggered, and a protection device which moves with said plasma burner for the purpose of protecting the electronic control unit from interference voltage resulting from said ignition process. According to the invention, in order to provide a plasma cutting machine based thereupon which satisfies high demands on interference immunity and operational safety, it is suggested that the protection device contains an electronic circuit which comprises said electronic control unit for the distance sensor, a protection switch having a plurality of protection levels for the purpose of reducing the interference voltage, and an interface to a machine control system.

A swirl ring component of a contact start plasma arc torch is provided. The swirl ring component includes a hollow body formed of a front portion and a rear portion along a longitudinal axis and defining an exterior surface and an interior surface. The swirl ring component also includes one or more gas passageways extending from the exterior surface to the interior surface in the front portion of the hollow body and a resilient element disposed relative to the interior surface in the rear portion of the hollow body and configured to pass at least a pilot arc current to an electrode body. The swirl ring component further includes a shoulder portion configured to retain the resilient element in the hollow body.