Before clarifying this question, I recall that the plasma is considered the fourth state of matter after solid, liquid and gas. The plasma sewn for a cluster of positive ions and neutral atoms, free electrons. And gas obtained by heating to extremely high temperatures. Changes in states of matter involves a certain quality of heat (latent heat of transformation) and to transform water into steam is necessary to produce heat. In the same way. The arc gas supplies heat to take the plasma state. Later when the plasma returns to its gaseous state returns the same amount of heat.

The process of plasma arc cutting, also called PAC (plasma arc cutting), separating metal using an arc constrained to melt a localized area of the workpiece at the same time removing the molten material with a high speed jet ionized gas that leaves the hole of constriction. The plasma is an ionized gas, hence the name of the process. The plasma arc usually operate at temperatures of 10 000 ° 14 000 ° C. Below is an outline of how this process:

A plasma arc is a gas which is heated by an arc to reach a state of at least partial ionization, allowing you to conduct an electrical current. In any plasma arc exists, but the term plasma arc torches applies to using a constricted arc. The main feature that distinguishes the plasma arc torches of other arc torches is that for a current and gas flow rate given, the arc voltage is higher in the constricted arc torch. The arc is constricted by passing through a hole in the electrode. When gas passes through the arc plasma is heated rapidly to a high temperature, it expands and accelerates as it passes through the constriction hole into the workpiece.

The intensity and speed of the plasma depend on a number of variables, among which are the type of gas, its pressure, the flow pattern, the electric current, the size and shape of the hole and its distance from the piece of work. The process works with direct current, straight depolaridad. The orifice directs a stream of superheated plasma from the electrode to lapieza work. When the arc melts the workpiece, the high velocity jet expels the molten metal to form the cut. The cutting arc is connected or “transferred” WORKING piece, so-called transferred arc.

To start the arc cutting method is used starting with pilot arc is an arc between the electrode and the tip of the torch. This arc sometimes called non-transferred arc because it is transferred or connected to the workpiece, as does the transferred arc. The pilot arc provides an electrically conductive path between the electrode of the torch and the workpiece so that you can start cutting the main arch.

The technique of starting with pilot arc most common is to make a spark of altafrecuencia between the electrode and the tip of the torch, the pilot arc is established in the resulting trayectoionizado. When the torch gets close enough to the workpiece so that the pen pilot arc or flame touch it, establishing a electrically conductive path between the electrode and the workpiece. The cutting arc will follow this path to the workpiece.

A BIT OF HISTORY …

The CAP was invented in the mid-1950s and achieved commercial success soon after its introduction in industry. The ability of the process of cutting any electrically conductive material made it particularly attractive for cutting non-ferrous metals which could not be cut using the process of oxy-fuel gas cutting (OFC). At first it was used for cutting stainless steel and aluminum, but as they develop the process was to have an advantage over other cutting processes for cutting carbon steel as well as nonferrous metals.

ADVANTAGES OF THE PROCESS

* Compared with mechanical cutting processes, the amount of force required to hold the workpiece in place and move the torch (or vice versa) is much lower for the process of plasma arc cutting, which makes no contact

* Compared with the OFC, the plasma cutting process operates in a much higher energy level, allowing higher cutting speeds.

* The PAC has the advantage to start immediately, without preheating. The instant start is particularly advantageous for applications involving interrupted cutting, like cutting meshes.

DISADVANTAGES OF THE PAC

* Compared to most mechanical methods Decorte, presents hazards such as fire, electric shock, intense light, smoke and fumes, and noise levels that are probably not present in mechanical processes.

* PAC is difficult to control as precisely as some mechanical processes to work with close tolerances.

* Compared with the OFC, the PAC team tends to be more expensive, requires electrical power and present danger of electrical shock.

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The calorific value of the jet (about 18 000 ° C) causes an almost instantaneous merger that spreads throughout the thickness of the piece, the jet is powerful enough to eject molten metal from the point of cutting. The plasma cutting allows cutting of sheet metal over thicknesses from 0 to 70 mm with an accuracy of plus or minus 0.2 mm.

The use of the torch plasma cutting should be mandatory in specially ventilated or outdoors due to release of toxic gases generated by the very high working temperatures. Some cutting systems include plasma water supply in the form of a calibrated jet which springs from the plasma torch, allows the metal to cool soon after plasma cutting, also avoiding the emission of these gases.

The plasma cutting torches are also used with a digital controller. Manufacturers build CNC cutting tables, some incorporating the torch on the table. The Modern CNC plasma equipment are capable of multi-axis cutting on thick materials. I therefore propose that one of these tables CNC plasma cutting, ESAB brand, built in 1994. It is equipped with a torch Hypertherm Max 200 and the table may include a format sheet 6000×1500mm.

The mark is the CNC ESAB NCE 280 Control.

This machine is available and visible in the United Kingdom for a price of 25,300 € HT
You can find this machine and several other cutting machines plasma in our catalog Exapro. Eu.

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