Plasma cutters are an incredibly useful and versatile piece of sheet metal machinery; it is able to pass through sheet metal with very little resistance and extreme precision, producing clean cuts of sheet metal that go on to be used in construction, transport and more. In this blog, we give you the basics on how plasma cutters work, as well as how to use them in order to achieve different sheet metal cuts.
What is Plasma?
Plasma is one of the four states of matter (the others being solid, liquid, and gas) and can be achieved by heating gas to extremely high temperatures. Plasma differs to gas in that its electrons are negatively charged and are not bound to the nucleus (which is positively charged). Instead, plasma electrons are able to move freely around the atom. Because plasma is ionised (made of charged particles), it is strongly influenced by magnetic and electrical fields, and is able to carry an electric current. This ability is what makes it so useful in sheet metal fabrication.
When was the first plasma cutter invented?
Plasma arc technology was first harnessed in the 1940s during World War II as a means to aid the production of aircraft for the U.S. military. Traditional forms of welding were not fast or accurate enough, so the concept of using an inert gas fed through an electric arc in order to form sturdier, more precise joints was born. This technology was further developed and soon it was discovered that by restricting the opening of the inert gas flow to the nozzle, the particles of the electric gas arc could be altered to be much hotter and faster, allowing the electric gas arc to not only weld metal, but cut through it with extreme precision. Different gases were experimented with, along with voltage, nozzle size and flow rate, allowing plasma cutters to cut through many different grades of sheet metal.
How do plasma cutters work?
Today, there are many varieties of plasma cutter, from industrial sized plasma cutters with robotic arms, to compact handheld plasma cutters. Despite the many types of and uses for plasma cutters, they all work using the same principle. First, pressurised gas (such as nitrogen, argon, oxygen etc.) is sent down a small channel, the centre of which holds a negatively charged electrode. When power is applied to this electrode and the tip of the nozzle is applied to the metal workpiece, an electrical circuit is created, resulting in a powerful spark between the electrode and the metal. This spark heats the inert gas as it passes through the channel, turning it into a stream of extremely hot (around 16,649 C), incredibly fast (6,096 m/sec) stream of plasma. When this plasma comes into contact with the metal it reduces the metal into molten slag, cutting it away from the rest of the workpiece. The plasma itself conducts an electrical current, allowing a continuous arc as long as power is supplied to the electrode and the plasma is in contact with the metal. The cutter nozzle has a second set of channels that release a constant flow of shielding gas, which control the radius (and in turn, thickness of cut) of the plasma beam, and protect the cut against oxidisation.
Plasma cutters in industry
Plasma cutters are used in many industries, from industrial scale construction and transport fabrication (automobiles, ships and planes), right down to small business (for example, locksmiths) and the arts. Although plasma cutters face competition from the newer technology of laser cutting, they are generally more affordable and are still an evolving technology with the introduction of modifications like CNC (Computer Numerical Controls).
If your business requires a plasma cutter for sheet metal fabrication, ACRA is able to help. We stock a range of new plasma cutters and can advise you on the best machine for your needs.