plasma cutter
plasma cutter machines for poles
How plasma cutter works
Plasma cutters send an electric arc through a gas conveyed through a constricted opening.Production processes through plasma cutters use a gas as a medium to transfer thermal power from an electrical power source to processed material.
Plasma cutter processing can be classified according to two plasma types: hot plasma and cold plasma, according to temperature (and consequent ionisation density) reached by heavy material..
In hot plasma heavy materials have the same average temperature of light particles (starting from 10.000 °C): plasma is in a condition of thermal balance. In cold plasma, gas is not in a condition of thermal balance: heavy particles have remarkably lower temperatures (around the 500-800°C) compared to electronic temperature.
Plasma temperatures and conditions influence their application: cold plasma applications are related to thermal processes requiring selective and limited material processing (selective fusion, heat treatment, structural changes, etc.) and chemical and physical reactions and transformations. Main hot plasma applications are related to welding, thermal spray and metal cutting.
Hot plasma cutting is achieved by producing an electric arc in gas subject to different electrical frequencies. The high-temperature ionised gas thus produced can remove, melt and modify material. The plasma beam is an easily controlled tool which does not directly contact processed material. It is also not subject to wear fretting.
Right from its initial applications (during the Eighties in Italy), standard plasma cutting has been acknowledged for its high operating efficiency (in terms of operation timing and costs) but also for insufficient cutting quality, often requiring further edge processing.
The cutting edge is rounded, covered in seams and grooves with very bad surface finish. The cutting groove is wide and flared and the trailing edge is often impaired due to burrs caused by rapid melted metal solidification. The heat-worked area is wider and subject to residual tension, metallurgic and structural distortions and variations.
Plasma cutting quality has remarkably improved due to the introduction of high-definition plasma (High Tolerance Plasma Arc Cutting, HTPAC) during the Nineties. High-definition plasma cutting is the result of the improvement of previous technologies and it has therefore in part replaced standard plasma cutting especially in low-depth processing.
However, considering such significant improvements (clean outlines, burr-free edges, limitation of the heat-worked area in sufficiently squared edges) plasma cutting has been used not only for material cutting (in order to allow subsequent processing) but also to achieve good surface and macro-geometric qualities in metal cutting.
HTPAC has therefore also been extended to similar processes in near net shape sheet cutting (no further processing required), thus competing with other non-standard high-quality technologies such as laser and hydro-abrasive jet cutting.
Negative standard plasma cutting reputation and relatively new HTPAC technologies are the reasons for limited attention on HTPAC research development. Only recently has greater attention been focused on this process which also offers to broader research potential..
Definition of plasma cutter: a tool used to cut steel and other materials. Plasma cutters send an electric arc through gas conveyed through a constricted opening. The gas can be air, nitrogen, argon, oxygen. etc. This increases gas temperature to the stage that it enters a 4th state of matter. We all are familiar with the first three states: i.e., solid, liquid, and gas. Scientists define this further state as plasma. As the metal being cut is part of the circuit, the plasma electrical conductivity causes the arc to transfer its working power. The restricted opening (nozzle) the gas passes through causes it to be conveyed at a high speed, like air passing through a Venturi in a carburettor. The high-speed gas cuts through the molten metal. The gas is also directed around the perimeter of the cutting area to shield the cut.
