Views: 121 Author: Site Editor Publish Time: 2020-11-18 Origin: Site
I have introduced you a powerful laser cutting machine before, so what is the difference between the plasma cutting machine and the metal processing equipment? What are the differences between the two? How do we choose? This article will introduce the plasma cutting machine in detail from the principle, operation, maintenance and other aspects.
Plasma cutting is a processing method that uses the heat of a high-temperature plasma arc to partially or partially melt (and evaporate) the metal at the incision of the workpiece, and uses the momentum of the high-speed plasma to remove the molten metal to form an incision. Plasma arc cutting machine is a machine that uses plasma cutting technology to process metal materials. Generally, it has dual-mode selection of automatic and semi-automatic cutting. It can digitally precisely control the cutting length and the operation is very convenient.
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 causes the workpiece to melt and be 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 component. 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.
The power supply of the main circuit is controlled by the contactor; the on-off of the gas is controlled by the solenoid valve; the control circuit controls the high-frequency oscillator to ignite the arc, and stops the high-frequency operation after the arc is established. In addition, the control circuit also has the following internal locking functions: the thermal switch operates and stops working.
The plasma cutting machine with different working gases can cut all kinds of metals that are difficult to cut with oxygen, especially for non-ferrous metals (stainless steel, carbon steel, aluminum, copper, titanium, nickel). The cutting effect is better; its main advantage is that the cutting thickness is not For large metals, the plasma cutting speed is fast, especially when cutting ordinary carbon steel sheets, the speed can reach 5-6 times that of oxygen cutting, the cutting surface is smooth, the thermal deformation is small, and there is almost no heat-affected zone.
The working gas that the plasma cutting machine can use (the working gas is the conductive medium of the plasma arc, it is the heat-carrying body, and at the same time the molten metal in the incision must be removed) has a significant impact on the cutting characteristics of the plasma arc, cutting quality and speed . Commonly used plasma arc working gases are argon, hydrogen, nitrogen, oxygen, air, water vapor and some mixed gases. Through the safe, simple, effective, multi-functional and environmentally friendly method of obtaining plasma from water vapor, thermal processing (cutting, welding, brazing, quenching, spraying, etc.) of metal with a thickness of 0.3 mm or more is carried out. It is the first in the history of the processing industry.
The plasma product "Multiplaz 3500" consists of a plasma gun and a chassis, with a total weight of 9 kg. The essence of the working process of the plasma equipment is as follows: An arc is generated between the nozzle (anode) and the electrode (cathode) inside the gun, which ionizes the moisture between them, thereby achieving a plasma state. 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 8 000 °С. In this way, non-combustible materials are cut, welded, welded, and other forms of heat treatment are processed.
2. Fast cutting speed and high precision. The cutting opening is small, neat and without slag drop. On the basis of the traditional numerical control system, the control method for cutting is improved to avoid secondary trimming processing.
3. Suitable for low-carbon steel, copper, iron, aluminum, galvanized, titanium and other metal plates.
4. High configuration of CNC system. Automatic arc ignition, stable performance, and the success rate of arc ignition is over 99%.
5. 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.
Ⅰ Before use and when cutting
1. Check and confirm that the power source, air source, and water source have no leakage, air leakage, water leakage, grounding or zeroing, and it is safe and reliable.
2. The trolley and the workpiece should be placed in an appropriate position, and the workpiece should be connected to the positive electrode of the cutting circuit, and there should be a slag pit under the cutting working surface.
3. The nozzle aperture should be selected according to the material, type and thickness of the workpiece, and the cutting power, gas flow and electrode shrinkage should be adjusted.
4. The automatic cutting trolley should run empty and select the cutting speed.
5. The operator must wear protective masks, welding gloves, hats, filter membrane dust masks and soundproof earmuffs. Persons who do not wear protective goggles are strictly prohibited from directly observing the plasma arc, and bare skin is strictly prohibited from approaching the plasma arc.
6. When cutting, the operator should stand upwind to operate. Air can be drawn from the lower part of the workbench, and the open area on the workbench can be reduced.
7. When cutting, when the no-load voltage is too high, check the electrical grounding, zero connection and the insulation of the torch handle. The workbench should be insulated from the ground, or a no-load circuit breaker should be installed in the electrical control system.
8. The high-frequency generator should be equipped with a shielding cover, and the high-frequency circuit should be cut off immediately after the high-frequency arc is used.
9. The use of thorium and tungsten electrodes should meet the requirements of Article 12.7.8 of JGJ33-2001.
Ⅱ Cutting operation and protection of cooperating personnel
1. The plasma cutting machine used on site should be equipped with rainproof, moisture-proof and sun-proof sheds, and corresponding fire-fighting equipment should be installed.
2. When cutting at high altitude, safety belts must be fastened, fire prevention measures should be taken around and below the cutting, and special personnel should be supervised.
3. When it is necessary to cut pressurized containers, sealed containers, oil drums, pipes, and workpieces stained with flammable gases and solutions, first eliminate the pressure in the containers and pipes, eliminate flammable gases and solutions, and then flush toxic, harmful and flammable Substance: For containers with residual grease, rinse them with steam and alkaline water first, and open the lid, confirm that the container is cleaned, and then fill with water before cutting. Measures to prevent electric shock, poisoning and suffocation should be taken when welding and cutting in the container. Air holes should be left for cutting sealed containers, and equipment and ventilation equipment should be installed at the inlet and outlet when necessary; the lighting voltage in the container should not exceed 12V, and the welder and the workpiece should be insulated; outside the container should be monitored by a special person. It is strictly forbidden to cut in the container that has been sprayed with paint and plastic.
4. It is strictly forbidden to cut pressure vessels and pipelines, live equipment, load-bearing structures, and containers containing flammable and explosive materials under pressure.
5. Welding and cutting are not allowed in the open air on rainy days. When working in a humid area, the operator should stand in a place covered with insulating materials and wear insulating shoes.
6. After the operation, the power supply should be cut off, and the air and water sources should be turned off.
1. Assemble the torch correctly
Install the cutting torch correctly and carefully, make sure that all parts are well matched, and ensure that the gas and cooling air flow. Install all the parts on a clean flannel to avoid dirt sticking to the parts. Add appropriate lubricating oil to the O-ring, subject to the brightening of the O-ring, no more.
2. Consumable parts should be replaced in time before they are completely damaged
Do not replace the consumable parts after they are completely damaged, because severely worn electrodes, nozzles and swirl rings will produce uncontrollable plasma arcs, which can easily cause serious damage to the cutting torch. So when the cutting quality is found to be degraded for the first time, the consumable parts should be checked in time.
3. Clean the connecting thread of the torch
When replacing consumable parts or daily maintenance and inspection, be sure to ensure that the internal and external threads of the cutting torch are clean. If necessary, clean or repair the connecting threads.
4. Clean the contact surface of electrode and nozzle
In many cutting torches, the contact surface between the nozzle and the electrode is a charged contact surface. If there is dirt on these contact surfaces, the cutting torch will not work normally and should be cleaned with hydrogen peroxide cleaning agent.
5. Check gas and cooling gas daily
Check the flow and pressure of the gas and cooling air flow every day. If you find that the flow is insufficient or leaking, you should stop the machine immediately to troubleshoot.
6. Avoid torch collision damage
In order to avoid collision damage to the cutting torch, it should be programmed correctly to prevent the system from running out of limits. The installation of an anti-collision device can effectively avoid the torch damage during collision.
7. The most common causes of torch damage
(1) The cutting torch collides.
(2) Destructive plasma arc caused by damage to consumables.
(3) Destructive plasma arc caused by dirt.
(4) Destructive plasma arc caused by loose parts.
8. Precautions
(1) Do not apply grease on the cutting torch.
(2) Do not overuse O-ring lubricant.
(3) Do not spray anti-splash chemicals while the protective cover is still on the cutting torch.
(4) Do not use the manual cutting torch as a hammer.
Plasma cutting machines are widely used in automobiles, locomotives, pressure vessels, chemical machinery, nuclear industry, general machinery, construction machinery, steel structures and other industries!
The advantages of plasma cutting machine are that the plasma arc energy is more concentrated, the temperature is higher, the cutting speed is faster, the deformation is small, and 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 certain pollution to the environment. For the medium thickness, 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 quality. It is not ideal to master it. It is not as simple as flame cutting. Plasma cutting guns should not be too many, because the cutting speed is faster, it is easy to be affected by the above factors, and the cutting quality is not the same. Generally speaking, for thin plate cutting, the surface quality of plasma cutting is better than that of fire filling cutting, and there is little slag.
In recent years, foreign manufacturers have developed a new technology called fine plasma or high-precision plasma, which has been introduced by domestic manufacturers. The effect is better. By improving the design of the cutting moment, the quality of the cutting surface of the workpiece is significantly improved, and the edge perpendicularity can reach 0-1.5°, which is especially beneficial for improving the cutting quality of thick plates. Due to the improved cutting gun, the electrode life has been increased 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. Therefore, plasma cutting of 4-30 mm steel plates is an ideal method, which can avoid the disadvantages of slow oxygen acetylene cutting speed, large deformation, severe cutting and severe slagging. Obtained a certain thickness of stainless steel and other materials.
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