Plasma is specified in Websters as a “collection of billed bits … having about equal numbers of favorable ions and electrons and displaying some homes of gas however varying from gas in being a good conductor of power …”. You can also consider it as an electrically warmed gas stream. I such as to think about it as a condition where every one of the electrons from every atom is moving from atom-to-atom, rather than simply orbiting. Despite what’s taking place inside a plasma stream, the means to cut steels with it is pretty simple. Take that stream of power flowing with gas, as well as restrict it through a tiny orifice. Now that stream is really thick as well as relocating very fast. The resulting stream can thaw and also blow through the majority of metals quite conveniently. That’s a plasma torch.
Plasma cutting torches generally make use of a copper nozzle to tighten the gas stream with the arc moving through it. That arc jumps from an electrode in the lantern to something else– typically the conductive material being cut. That’s a ‘moved arc’. There are some systems that make use of a ‘non-transferred’ arc where it leaps from the electrode back to the nozzle, but those are not normally made use of for reducing. To make sure that indicates that plasma cutting is only utilized for materials that are conductive, primarily light steel, stainless steel, and also lightweight aluminum. However great deals of various other steels and also alloys are conductive too, such as copper, brass, titanium, Monel, Inconel, cast iron, and so on. The issue is that the melting temperature level of some of those steels makes them challenging to reduce with a good quality edge.
The electrode is usually made from copper, but with a metal insert at the point where the arc connects. That’s due to the fact that the copper would certainly thaw also quick if the arc attached directly to it. Tungsten makes a wonderful electrode product, so lots of electrodes have a tungsten insert. Some smaller lanterns utilize a ‘pencil’ design electrode made completely out of tungsten with a sharp end. The trouble with tungsten is that it burns up in the existence of Oxygen. So when utilizing Oxygen or compressed air as the cut gas, the insert is made from a product called Hafnium. Hafnium lasts a lot longer in the existence of Oxygen, however, it still puts on a bit with each begin of the arc.
So why usage Oxygen in a plasma lantern? The very same factor you utilize Oxygen in an acetylene torch– the Oxygen in the plasma stream responds with mild steel. That is why pure Oxygen is just utilized when cutting mild steel, or ‘carbon steel’. That chemical reaction between the Oxygen in the plasma gas and also the base metal helps to accelerate the cutting procedure and also improves the edge of high quality. However given that Oxygen doesn’t have the very same response with Stainless-steel or Aluminum, less costly gases can be made use of for those steels, like Nitrogen or pressed air (which is mostly Nitrogen anyhow).
Various other specialty gases are occasionally used for various other objectives. Argon gas is utilized when plasma marking (a whole other topic). A mixture of Argon as well as Hydrogen is usually used when cutting thicker Stainless Steel or Light Weight Aluminum. Some individuals use a mixture of Hydrogen and also Nitrogen, or Methane and also Nitrogen when cutting thinner Stainless-steel. Each mixture has its benefits (enhanced cut top quality) and also its negative aspects (price & handling).
So those are several of the essentials of plasma cutting– an arc lugged in a stream of gas from an electrode with an orifice and after that right into the conductive metal that is being reduced. There are lots of various other considerations that I will certainly address later on, such as swirling gases, kerf, elevation control, arc starting, shield gas, and so on. However, whether it’s hand-held or placed on a CNC device, the essentials coincide.