In a previous article, we discussed the topic of plasma as a subject in physics. In this article, we will focus on its practical aspects. You will learn how a plasma cutting machine is built and how it works.
What does a plasma cutting machine comprise?
Power – supply system – upplied from an electric network and generating direct current (DC), with a voltage of 240-400 V. The total wattage rating of the power supply and its current capacity has a crucial influence on the thickness of the material to be cut. Its task is to supply the correct amount of energy to the ignition circuit.
Ignition circuit – is a typically a high frequency generator circuit that generates an AC voltage of 5 to 10 kV, with a frequency of 2 MHz.
Torch – it serves as both a holder for the nozzle and the electrode. It also provides cooling.
Chassis ground clamp – is attached to the material to be cut and used to close the ignition circuit through the torch and the material.
There are different methods of ignition.
Air plasma torches use a moving electrode or ‘backflow starting method’ to ignite the gas.
Using manual plasma cutter, you need to scratch or bring the nozzle close to the material. When the ground clamp is attached to the material to be cut, it can initiate an electric flow and so ignite an electric arc between the electrode and the material.
High kinetic energy arc is supported by a stream of compressed gas (usually air), passed through a gap in the nozzle which acts as a focus for the plasma flow. The flow is directed by means of a gas introduced in a swirling motion on the walls of the nozzle. A suitable positioning ensures that a stream with a thickness of 1 mm can be obtained. The set is cooled by gas or water.
Because both, the nozzle and the electrode are consumables, they need to be replaced when consumed.
The cutting process is based on high temperatures of 10,000 to 30,000 K and a very high plasma beam speed. It results in melting the material, oxidisation and removal from the narrow slit. As a consequence, the edge is smooth and requires little further machining.
All electrically conductive materials can be cut via plasma including those covered with paint. Thereby, it is necessary to clean the area under the chassis ground clamp.
The plasma cutter is best suitable for cutting:
- carbon steel
- cast iron
- acid resistant steel
- aluminium and its alloys
Below, there are some advice on the safe use of plasma units:
- Protect yourself against burns. Plasma cutting process involves very high temperatures!
- Protect your respiratory tract and vent the workroom properly!
- Protect your eyes and face from intense UV radiation!
- Avoid exposure to electromagnetic radiation from the electrical system units!
We encourage you to watch the video on YouTube. It presents the functional principles of the plasma source in an interesting way.
Feel free to check out our previous blog articles.
More coming soon!