Plasma cutting

A plasma cutter cuts metal by means of a plasma which is generated by an electric arc.

Operation

The plasma cutter consists of a power source, handpiece, ground cable, power supply and compressed air supply line. A plasma cutter creates an arc between a tungsten electrode and the workpiece. Plasma is an electrically conductive gas having a temperature of about 30,000 ° C. The arc is ignited usually with a high frequency ignition and constricted at the outlet of an insulated, water-cooled usually copper nozzle. Some systems use the lift-arc ignition, which is also used for the TIG welding equipment. In these devices, the burner is placed at the intersection of the workpiece and flowing a small current is not sufficient to cause damage to the burner. The gas flow pushes the torch from the workpiece surface, the arc ignites and the electronics of the welding current source increases the current of the strength required for the section. Due to the high energy density of the arc melts the metal, and is blown off by a gas jet, so that the kerf is produced. As a gas for blowing compressed air is often used. For a better kerf also shielding gas mixtures are used which prevent or reduce oxidation. Characteristic of plasma kerf is a rounding of the edge at the entry point.

Application in industry

In the metal processing hand - or machine- guided plasma cutter can be used. Depending on the current electrically conductive materials up to 200 mm thickness of the workpiece can be separated. Common hand plasma systems have up to 120 amperes, with the stronger mechanically guided plasma cutting systems, the amperage may be at about ten times to this value. Conventional systems use about 300 amps and can use it to pierce 70 mm black plate. With today's plasma technology distinguishes between conventional plasma cutting and precision plasma cutting. When precision plasma cutting without burrs of the cut lines, angularity of the cut or a bare metal surface as a criterion to be applied. Here, instead of compressed air used industrial gas, in order to achieve a better cutting quality, which is close to the quality of laser cutting. The advantages over the flame cutting with CNC plasma cutting machines are mainly used in about four times as high cutting speed and in the lower due to the high energy density heat distortion. In addition, plasma cutters can cut virtually all metals, while torch cutting is largely restricted to structural steels.

Application in rescue

Originally designed for industrial use plasma cutters, is used in a mobile variant in rescue work, for example by the fire brigade and the THW. Can a hydraulic spreader and a hydraulic cutter for lack of space not be used or prohibits the use of a cutting torch because of its difficult handling and significant thermal spread, is the plasma cutter is an ideal alternative represents the lower thermal expansion makes it possible to work closer to people. It is not possible to use a hydraulic cutter of hardened steel, as used in the steering column and in the control arm. There therefore frequently the plasma cutter is used. The equipment used generally reach a current of 20 to 60 A. With these it is possible to the rescue forces to cut up to 30 mm thick mild steel.