Plasma is a thermally high-heated, electrically conductive gas. That means that neutral atoms dissolve into ions and electrons by adding ionisation energy. This energy can be produced by very high temperatures or strong electric fields. Generally, plasma reacts like a gas with a neutral outside effect.
Plasma cutting is a thermal fusion cutting method which is realised with an electric arc constricted by a nozzle. The cutting process starts first with a pilot arc which is ignited between nozzle and electrode (cathode) by high voltage. The pilot arc has low energy and ionises partly the atoms between plasma torch and workpiece. As soon as the pilot arc touches the workpiece, the electric circuit closes and the main are is ignited by the increased power. The high thermal energy of the arc and the high kinetic energy of the plasma gas melt the material and the molten material is driven out of the kerf. The small heat affected zone and high cutting speeds are particularly huge advantages of this method.
Different process variants:
1.Dry Plasma Cutting
Dry plasma cutting is often referred to as conventional or standard plasma cutting. However, the historic development should be regarded in a more differentiated way. Conventional plasma cutting means that the arc is only focussed by the inner diameter of the nozzle
2.Underwater Plasma Cutting
The development of underwater plasma cutting originated in the special requirements of industrial cutting applications. Among other things, the noise pollution, radiation and dust exposure as well as material distortions caused by heat input should be reduced.
Materials are cut under the water surface which means that the plasma beam has to be shielded from the water. This can be realised by additionally using a swirl gas flowing around the plasma arc. For physical reasons, this process requires a higher energy input compared to dry plasma cutting, thus reducing the cutting speeds that can be achieved. Furthermore, it is not possible to reach the cutting quality of a dry plasma cut.
3.Plasma Cutting with HiFocus
When using the HiFocus technology for plasma cutting, a swirl gas is added which rotates around the plasma beam at very high speed and constricts the plasma beam heavily. Originally, this method comes from underwater plasma cutting and has been adopted for dry plasma cutting, too, because of its positive features: The rotation of the swirl gas has the effect that the plasma beam is strongly focussed, stabilised and protected. A big advantage for users is that this technology allows nearly rectangular cut surfaces within a broad range of material thicknesses. Further, the HiFocus plasma cutting systems are characterised by excellent cutting results when cutting thin sheets. In connection with the latest inverter technology the HiFocus technology allows highest cutting quality when cutting thin sheets and is therefore a serious competition for laser cutting.
4.Marking, Notching and Punching with Plasma
MMarking, Notching, Punching and Gouging with PlasmaLarge orders – whether for national or international customers – require a good and traceable flow of materials. The larger such orders are the more important are identification marks on the material. The industry increasingly recognizes and uses the advantages of plasma marking because this method saves production steps and, thus, incidental expenses can be reduced:
Variable marking intensity with one system
No additional equipment necessary
Marking with the same tools – no change necessary
Simplest integration into CNC control unit
The high-precision plasma cutting systems of the HiFocus series with inverter technology – marked with an „i“ in their names – already have this marking function. It allows cutting and marking without changing the consumables of the torch. These inverter power sources achieve the best marking quality in the plasma industry in particular due to the extremely low marking currents from 5 A and the use of argon as marking gas.
In any case, users can decide on the depth and width of the marking. Almost any marking task can be realized with plasma, from simple annealing colours that are invisible after finishing to deeper notches and punching marks.