We will explain the CNC Plasma Cutting Machine operating principle which uses plasma metal cutting technology with high temperature and high movement speed of airflow from the cutting head’s mouth to break metal materials. Ngoc Viet CNC is currently the leading manufacturer of this model in Vietnam nowadays.
Plasma cutting mechanism
Plasma understood according to science as a state of matter which is formed by strongly ionized substances. The majority of atoms or molecules are nuclei, and electrons move almost freely between these nuclei.
The plasma cutting machine work based on the principle of plasma gas to carry out the metal cutting process. It operates by using very high temperatures and the extremely high-speed airflow from the nozzle to melt and blowfly the metal part opposite it from the cutting slot. When appropriately applied the plasma cutting machine, the cutting line will be straight and less susceptible to slag. Also, moderate cutting speeds can make the cutting process gently.
The quality of the cutting line when cutting with a plasma cutter depends on the current intensity, the type of gas used, the cutting speed and the distance from the cutting head to the cutting object.
If you want to learn about CNC Plasma Cutting Machine, kindly read the following article: Comprehensive information about CNC Plasma Metal Cutting Machine
What does the plasma cutting system include?
A basic plasma cutting system incaludes a power supply unit, an arc start circuit and a cutting head. The components of the power supply system, the ionization capacity and the control process are necessary to produce high quality and high-yield cutting on various types of metals.
The power supply kit is a continuous one-way power source with a voltage of 240 to 400 VDC. The output current of the power supply is adjusted according to the desired speed and material thickness. The main function of the power supply is to provide accurate energy to maintain the plasma arc after ionization.
The arc start circuit is a high-frequency generator that generates an alternating voltage of 5,000 to 10,000 volts at 2 million Hz (2MHz). This voltage is used to create an intense arc inside the cutting head to ionize the gas, thus creating plasma.
The nozzle is used to hold consumables such as nozzles (cutters) and electrodes, supplying coolant (gas or water) to these parts. Nozzles and electrodes function to compress and maintain the plasma jet.
What kind of gas used to generate Plasma?
The plasma gas-forming environment must ensure: creating an effective shape for the cutting arc; creating high-quality cutting surface; efficiently transferring heat into the material object; lasting long life for cutting torch parts; Adding heat in the cutting process through exothermic reaction and ensuring to be economical, safe.
Commonly gases used to create plasma are nitrogen, argon, hydrogen, oxygen, compressed air. Inert gas leaves the cleanest cut surface, suitable for non-ferrous metals. Atomic O2 has the effect of improving the transmission of energy into the arc for the cutting object through the mechanism of separation – recombination. Oxygen-containing gas has a high energy efficiency to cutting which creating an exothermic reaction of oxygen with the cutting material, giving high productivity. The most used gas is compressed air. It is possible to add water to the cutting torch to gain steel cutting surface quality and increase cutting speed. It is also possible to add flammable gas to increase the cutting speed of copper and copper alloys and enhance the quality of the cutting surface.
Operating principle of CNC Plasma Cutting Machine
The power supply and arc start circuit are connected via internal pipes and wires in the CNC plasma cutting machine. These pipes and wires provide the appropriate electric, gas and arc current to the cutting heads to bait and maintain the material cutting process using CNC plasma cutting machine. The operating principle of the CNC plasma cutting machine includes the following steps:
Firstly, a start signal will be sent to the power supply unit, which is a current of 280 VDC activated. The gas flow begins to move to the cutting edge of the CNC plasma cutter. This voltage is measured from the electrode to the nozzle of the CNC plasma cutting machine. This nozzle is connected to the positive pole of the power supply via a resistor and relay. Meantime, the cutting material is connected directly to the anode of the power supply. Accordingly, airflow passes through the nozzle before going out of the environment. In phase 1, the voltage circuit is opening, so there is no arc emitted as well as current flows through the DC source.
2. Create a bait arc stream
Once the gas flow has stabilized, the arc circuit is started. A high voltage of 5000 to 10000 VAC is generated by the arc circuit with very high frequency. At this time, a current will be released between the electrode and the nozzle inside the cutting head where the gas used to create plasma go through before exiting the environment. The energy transferred from the high-frequency spark to the gas stream, which leads to the airflow ionized and able to conduct electricity. As a result, a conductive line between the electrode and the nozzle is created. The arc is formed pushed by the airflow to the nozzle hole, then going out and forming a priming arc stream.
3. Finish creating primer arc
When the nozzle is moved closer to the cutting material, the plasma arc current will strike the cutting material as a current path to the anode of the power supply. Unlike the nozzle connected to the anode, this arc current is not limited by resistors. The power supply unit will recognize the current flowing through the cutting material, at this time, the arc starter will automatically stop working, and the pilot relay will be opened. The ionization current is maintained by energy from the plasma arc of direct current.
4. The process of cutting materials start
The arc can melt metal cutting materials because of its extremely high temperature. Also, It melts, punctures and blows the molten material down the cutting line thanks to the extremely high velocity of the gas stream. At this point, the cutting process starts, and the machine is automatically controlled to follow the lines already drawn on the computer.
5. Cutting process and height control
The CNC plasma cutting machine move along the line preset as the drawing, the height controller of the CNC plasma simultaneously work. Depending on the warping of the cutting material that the height controller will automatically sense the distance and controls the height appropriately, which ensure the height from the nozzle to the material to be stable, and cutting products be always as expected.