How does plasma cutting actually work? How it is that plasma is able to cut through such a hard material as metal? Why is it so important that we use plasma assist gases? The following is a brief overview of some of the science behind plasma cutting technology, how it works, and why it is so tremendously powerful:
The Plasma
Plasma cutters operate by sending pressurized gas through a small channel. These gases are referred to as primary plasma cutting gases.
These primary plasma cutting gases include:
- Oxygen
- Compressed air
- H35 – 65% Argon, 35% Hydrogen
- F5 – 95% Nitrogen, 5% Hydrogen
Since they are concentrated through such a narrow space their pressure is increased significantly. At the center of this opening there is a negatively charged electrode which passes an electric current through the gas. The stimulation of the gas atoms produces both negatively and positively charged ions that continue to collide together until the very hot state of plasma is created.
Creating the Current/Connection
When power is applied to the negative electrode a circuit is created between itself and a positive electrode. The metal plate being cut acts as the positive electrode and attracts the plasma energy toward it. If power is continued to be supplied, and contact is maintained with the metal then the electric current that the plasma conducts will continue to exist.
Controlling the current
The plasma is an unpredictable state, so in order to control it, shielding gas or assist gas is released. These are also known as secondary gases. They are not a part of the actual plasma state, but assist in the control of the current. They not only aid in directing the plasma, but also ensure that the area where the plasma touches the metal plate is protected so that the connection is maintained. The primary gases mentioned earlier can also be used as assist gases. To read more about assist gases read Plasma Assist Gases
Making the Cut
Due to the extreme heat directed at the metal plate by the plasma torch, (as much as 30000 degrees Fahrenheit), the metal is melted. This leads to the achievement of an effective cut in the material.
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