The most basic way to explain the process behind plasma cutting is to think of it as controlled melting. It is very accurate strategic controlled melting.
A compressed gas is blown through a nozzle at high pressure, an electrical arc is formed within the gas between an electrode, which is often integrated into the nozzle, and the material that you are cutting. The electrical arc creates a channel of plasma by ionizing some of the gas that is being blown through the nozzle. The Plasma torch passes enough electricity through the gas and the arc that plasma becomes hot enough to melt the material in a controlled manner. As the material becomes hot enough the pressure from the gas and plasma is enough to force the molten material away and leave you with a clean cut.
This process is the same for any type of plasma cutting. CNC plasma cutting tables can cut much thicker materials than hand-held plasma torches can. Cutting tables can cut metal three times as thick as hand-held torches.
Computer Numerically Controlled Cutting Tables
CNC cutting tables are controlled either by specific computers made to run cutting tables or PCs that have been adapted to control them. The process involves Computer aided design which lets you draw your desired cuts onto the screen. Once you have done this, the cutting table can be programmed to cut the material the based on your design. There are varying levels of control from machine to machine however, generally, you can pause and set speeds for the cutting.
This accuracy is possible due to the sharp clean cuts made by a plasma torch. Intricate designs can be cut in a fraction of the time that would be needed to do so manually. No metal shards are left after cutting which is another important advantage to plasma cutting.
There are 3 main types of CNC cutting tables, 2 dimensional, 3 dimensional and tube cutting. Their uses and prices can be particularly different.
2 dimensional CNC cutting tables are most common type of cutting table, and often the most affordable, they are able to cut materials at a 90 degree angle up to an average of 150mm thick.
3 dimensional CNC cutting tables differ in that they have an extra axis of rotation for the cutting torch. This means a lot more flexibility and is particularly useful to prepare metal for welding. Although these tables are more expensive than their 2 dimensional counterparts they can save you a lot of money. Due to the flexibility of the extra axis you can prepare metal for welding without any extra processes. Typically, these cutting tables cut out the need to grind or machine the metal further before welding.
Tube plasma cutting typically has a stationary plasma torches whilst the material is automatically passed under the torch accordingly. This is particularly useful in welding preparation and in the HVAC industry. Also, some tube plasma cutters have an extra axis much like 3 dimensional cutting tables which, again, are used for welding preparation.
In fact, over the last decade plasma torches have reached near laser levels of accuracy. It is now possible to manufacture the torches with increasingly smaller nozzles and therefore a smaller plasma arc to cut with. This, again, reduces the need for any extra preparation for metal before welding.