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Plasma cutting machines are machines that use plasma cutting technology to process metal materials. It is a processing method that uses the heat of a high-temperature plasma arc to partially melt the metal at the incision of the workpiece. It uses the momentum of the high-speed plasma to remove the molten metal to form an incision.
2. Plasma Cutting Machine Features
The plasma cutting machines with different working gases can cut all kinds of metals that are difficult to cut with oxygen, especially for non-ferrous metals (aluminum, copper, titanium, nickel). And the cutting effect is better; its main advantage is when cutting metals with a small thickness. Plasma cutting speed is fast, especially when cutting ordinary carbon steel thin plates. The speed can reach 5-6 times that of the oxygen cutting method, the cutting surface is smooth. The thermal deformation is small, and there is almost no heat-affected zone.
Plasma cutting machines, the available working gas (working gas is the conductive medium of the plasma arc. It is also the heat-carrying body, and at the same time the molten metal in the incision must be removed) has obvious effects on the cutting characteristics, cutting quality and speed of the plasma arc. Influence. Commonly used plasma arc working gases are argon, hydrogen, nitrogen, oxygen, air, water vapor, and some mixed gases.
We widely use plasma cutting machines in automobiles, locomotives, pressure vessels, chemical machinery, nuclear industry, general machinery, engineering machinery, steel structures, and other industries.
Through the safe, simple, effective, multi-functional, and environmentally friendly method of obtaining plasma from water vapor. It can carry out the thermal processing (cutting, welding, brazing, quenching, spraying, etc.) of metal with a thickness of 0.3mm or more in the metal. It is the first in the history of the processing industry.
The essence of the working process of the plasma equipment is this: an arc can generate between the nozzle (anode) and the electrode (cathode) inside the gun. Which ionizes the moisture between them, thereby achieving the state of plasma. At this time, the ionized vapor is ejected from the nozzle in the form of a plasma jet under the pressure generated inside. And its temperature is about 8000°C. In this way, it can cut and weld the non-combustible materials, and process other forms of heat treatment.
3. Plasma Cutting Machine Structure
- The frame adopts a fully welded structure, which is firm and reasonable, simple to operate, and durable.
- Fast cutting speed and high precision. The cutting opening is small, neat, and there is no slag drop phenomenon. On the basis of the traditional numerical control system, the control method for cutting is improved. And the secondary trimming processing is avoided.
- Suitable for low-carbon steel, copper, iron, aluminum, galvanized, titanium and other metal plates.
- The CNC system has a high configuration. Automatic arc ignition, stable performance, and the success rate of arc ignition is over 99%.
- Support standard G code path files generated by Wentai, Beihang Haier, ARTCAM, Type3 and other software. The control system adopts U disk to exchange processing files, which is convenient and quick to operate.
4. Plasma Cutting Machine Working Principle
Plasma is a gas that is heated to a very high temperature and is highly ionized. It transfers the arc power to the workpiece. The high heat melts the workpiece and is blown off, forming the working state of plasma arc cutting.
After the compressed air enters the cutting torch, it is distributed by the gas chamber to form plasma gas and auxiliary gas. The plasma gas arc serves to melt the metal, while the auxiliary gas cools the various parts of the torch and blows off the molten metal.
The cutting power supply includes two parts: the main circuit and the control circuit. The electrical principle: the main circuit includes a contactor, a three-phase power transformer with high leakage reactance, a three-phase bridge rectifier, a high-frequency arc ignition coil, and a protection element. The high leakage reactance leads to a sharp external characteristic of the power supply. The control circuit completes the entire cutting process through the button switch on the cutting torch:
Pre-venting—main circuit power supply—high-frequency arc ignition—cutting process—removing arc—stop.
It can control the power supply of the main circuit by the contractor; it can control the gas flow by the solenoid valve; the control circuit controls the high-frequency oscillator to ignite the arc. And stops the high-frequency operation after establishing the arc.
In addition, the control circuit also has the following internal locking functions: the thermal switch operates and stops working.
5. Production Application
The advantages of the plasma cutting machine are that the plasma arc energy is more concentrated. The temperature is higher, the cutting speed is faster, and the deformation is small. It can also cut stainless steel, aluminum, and other materials.
The disadvantages of plasma cutting are that the arc is strong, the noise is large. And there is a lot of dust, which has a certain degree of pollution to the environment. For many medium thicknesses, underwater plasma cutting is used, and the cutting thickness is also limited. Similarly, gas flow, arc length, telegraph quality, current size, and cutting speed all affect the quality. It is not as simple as flame cutting. Plasma cutting guns should not be too many, because the cutting speed is faster. The above factors easily affect it, and the cutting quality is not the same. Generally speaking, for thin plate cutting, the surface quality of plasma cutting incision is better than that of fire filling. And there is little slag.
In recent years, foreign manufacturers have developed a new technology called fine plasma or high-precision plasma. Many domestic manufacturers have introduced it. The effect is better. By improving the design of the cutting moment, significantly improved the quality of the cutting surface of the workpiece. The verticality of the shaft edge can reach 0-1.5°, which is especially beneficial for improving the cutting quality of thick plates. Due to the improved cutting gun, it has increased the electrode life several times. However, the distance between the cutting torch and the steel plate is relatively high, and the height sensor on the cutting torch is required to be more sensitive and the cutting torch to react faster when moving up and down.
Therefore, plasma cutting 4-30 mm steel plate is an ideal method, which can avoid the shortcomings of slow oxygen-acetylene cutting speed, large deformation, severe cutting, and severe slagging. Obtained a certain thickness of stainless steel and other materials.
6. Cutting Specifications
- No-load voltage and arc column voltage
The plasma cutting power supply must have a high enough no-load voltage to easily start the arc and make the plasma arc burn stably. The no-load voltage is generally 120-600V, and the arc column voltage is generally half of the no-load voltage. Increasing the arc column voltage can significantly increase the power of the plasma arc, thereby increasing the cutting speed and cutting larger thickness metal plates. It often does not reach the arc column voltage by adjusting the gas flow rate and increasing the internal shrinkage of the electrode, but the arc column voltage cannot exceed 65% of the no-load voltage, otherwise, the plasma arc will unstable.
- Cutting current
Increasing the cutting current can also increase the power of the plasma arc, but the maximum allowable current will limit it, otherwise, the plasma arc column will become thicker, the slit width will increase, and the electrode life will decrease.
- Gas flow
Increasing the gas flow can not only increase the arc column voltage but also enhance the compression effect on the arc column, so that the plasma arc energy is more concentrated and the jet force is stronger, thus improving the cutting speed and quality. However, if the gas flow is too large, it will shorten the arc column, increase the heat loss, and weaken the cutting ability.
- The amount of electrode shrinkage
The so-called shrinkage refers to the distance between the electrode and the end surface of the cutting nozzle. A proper distance can make the arc be well compressed in the cutting nozzle, and obtain a plasma arc with concentrated energy and high temperature for effective cutting. If the distance is too large or too small, it will seriously burn the electrode, it will burn out the cutting tip, and it will reduce the cutting ability. The shrinkage is generally 8-11mm.
- Cutting nozzle height
The height of the cutting nozzle refers to the distance from the end of the cutting nozzle to the surface of the workpiece to be cut. The distance is generally 4~10mm. It is the same as the internal shrinkage of the electrode, and the distance must be appropriate to give full play to the cutting efficiency of the plasma arc, otherwise, it will reduce the cutting efficiency and cutting quality or cause the cutting nozzle to burn out.
- Cutting speed
The above various factors directly affect the compression effect of the plasma arc, that is, the temperature and energy density of the plasma arc. The high temperature and high energy of the plasma arc determine the cutting speed, so the above various factors are related to the cutting speed. On the premise of ensuring the cutting quality, it should increase the cutting speed as much as possible. This not only improves productivity but also reduces the amount of deformation of the cut parts and the heat-affected area in the kerf area. If the cutting speed is not appropriate, the effect is opposite, and the sticking slag will increase and the cutting quality will decrease.