Air Plasma Cutting
Plasma cutting is a process that is used to cut steel and other metals of different thicknesses (or sometimes other materials) using a plasma torch. In this process, an inert gas (in some units, compressed air) is blown at high speed out of a nozzle; at the same time an electrical arc is formed through that gas from the nozzle to the surface being cut, turning some of that gas to plasma. The plasma is hot enough to melt the metal being cut and moves fast enough to blow molten metal away from the cut.
The HF type plasma cutting machine uses a high-frequency, high-voltage spark to ionize the air through the torch head and initiate an arc. These do not require the torch to be in contact with the job material when starting, and so are suitable for applications involving computer numerical controlled (CNC) cutting. More basic machines require tip contact (scratch) with the parent metal to start and then gap separation can occur similar to DC type TIG welders. These more basic type cutters are more susceptible to contact tip and shield damage on starting.
The Pilot Arc type uses a two cycle approach to producing plasma, avoiding the need for initial contact. First, a high-voltage, low current circuit is used to initialize a very small high-intensity spark within the torch body, thereby generating a small pocket of plasma gas. This is referred to as the pilot arc. The pilot arc has a return electrical path built into the torch head. The pilot arc will maintain itself until it is brought into proximity of the workpiece where it ignites the main plasma cutting arc. Plasma arcs are extremely hot and are in the range of 25,000°C.
Plasma is an effective means of cutting thin and thick materials alike. Hand-held torches can usually cut up to 38mm thick steel plate, and stronger computer-controlled torches can cut steel up to 150 mm thick. Since plasma cutters produce a very hot and very localized "cone" to cut with, they are extremely useful for cutting sheet metal in curved or angled shapes.
Plasma cutting consumables : are the parts in the torch that wear out over time. How often you need to change the consumables depends on a number of factors, including :-
- thickness and type of material being cut
- length of the everage cut
- air quality (the presence of oil, moisture, or other contaminants)
- whether you are piercing or dege-staring
- how well the proper torch-to-work distance is maintained with unshielded consumables
- proper pierce height
- which consumables you are using
Plasma torches were once quite expensive. For this reason they were usually only found in professional welding shops and very well-stocked private garages and shops. However, modern plasma torches are becoming cheaper, and now are within the price range of many hobbyists. Older units may be very heavy, but still portable, while some newer ones with inverter technology weigh only a little, yet equal or exceed the capacities of older ones.
Industries that use plasma cutters :-
This list can be endless, but a partial one would include: general fabrication, manufacturing, facility and equipment maintenance, agricultural equipment repair, car and truck repair, structural steel building construction, shipyard, container fabrication and repair, energy, HVAC/mechanical contractors, metal artwork, prototype faculties, aviation restoration, and of course the automotive industry.
Modern industry depends on the manipulation of heavy metal and alloys: We need metals to build the tools and transportation necessary for day-to-day business. For example, we build cranes, cars, skyscrapers, robots, and suspension bridges out of precisely formed metal components. The reason is simple: Metals are extremely strong and durable, so they're the logical choice for most things that need to be especially big, especially sturdy, or both.
The funny thing is that metal's strength is also a weakness: Because metal is so good at resisting damage, it's very difficult to manipulate and form into specialized pieces. So how do people precisely cut and manipulate the metals needed to build something as large and as strong as an airplane wing? In most cases, the answer is the plasma cutter. It may sound like something out of a sci-fi novel, but the plasma cutter is actually a common tool that has been around since World War II.
Conceptually, a plasma cutter is extremely simple. It gets the job done by harnessing one of the most prevalent states of matter in the visible universe.