Analysis of arc instability fault in plasma cutting machine

The stability of the arc of the plasma cutting machine directly affects the cutting quality, and the instability of the plasma arc can lead to defects such as jagged indentation and accumulation of tumors, which also leads to a decrease in the life of related components of the control system, and frequent replacement of nozzles and electrodes. In response to this phenomenon, analysis and solutions are proposed.

1. The air pressure is too low

When the plasma cutting machine is working, if the working pressure is far lower than the pressure required by the specification, this means that the discharge speed of the plasma arc is weakened, and the input air flow is less than the specified value. At this time, a high energy, high speed plasma arc cannot be formed. As a result, the quality of the incision is poor, the cut is not penetrated, and the incision accumulates. The reasons for the lack of air pressure are: insufficient air input to the air compressor, low pressure regulation of the air regulator valve of the cutting machine, oil stain in the solenoid valve, and unobstructed air passage.

The solution is to observe the output pressure display of the air compressor before use. If the requirements are not met, adjust the pressure or repair the air compressor. If the input air pressure has reached the required level, check whether the air filter pressure reducing valve is adjusted correctly, and the gauge pressure display can meet the cutting requirements. Otherwise, the air filter regulator should be routinely maintained to ensure that the input air is dry and free of oil. If the input air quality is poor, oil will be generated in the solenoid valve, the valve core is opened, and the valve port cannot be fully opened. In addition, the pressure of the torch nozzle is too low, and the solenoid valve needs to be replaced; if the cross section of the gas path is small, the air pressure will be too low, and the air pipe can be replaced according to the instructions.

2. The air pressure is too high

If the input air pressure is far above 0.45 MPa, after the plasma arc is formed, the excessive airflow will blow the concentrated arc column, dispersing the energy of the arc column and weakening the cutting strength of the plasma arc. The causes of excessive air pressure are: improper input air conditioning, excessive adjustment of the air filter regulator or failure of the air filter regulator.

The solution is to check if the air compressor pressure is properly adjusted and whether the air compressor and air filter pressure reducing valve are out of pressure. After the start-up, such as the rotary air filter pressure reducing valve adjustment switch, the gauge pressure does not change, indicating that the air filter pressure reducing valve is malfunctioning and needs to be replaced.

3. Torch nozzle and electrode burnout

If the nozzle is not properly installed, if the thread is not tightened, the gears of the equipment are not properly adjusted. When the torch that needs water cooling is working, the cooling water that does not flow as required and the frequent arcing will cause premature nozzle damage.

The solution is to correctly adjust the gears of the equipment according to the technical requirements of cutting the workpiece, and check whether the nozzle of the torch is installed firmly. The nozzle that needs to pass the cooling water should circulate the cooling water in advance. When cutting, adjust the distance between the torch and the workpiece according to the thickness of the workpiece.

4. Input AC voltage is too low

The use of the plasma cutting machine has large-scale power facilities, and the main circuit components inside the cutting machine are faulty, which may cause the input AC voltage to be too low.

The solution is to check whether the plasma cutting machine is connected to the grid and has sufficient carrying capacity, and whether the power cord specifications meet the requirements. The plasma cutting machine should be installed away from large electrical equipment and places with frequent electrical interference. During use, regularly clean the dirt and components on the cutting machine, and check if the wires are aging.

5. The ground wire is in poor contact with the workpiece

Grounding is an essential preparation before cutting. If the special grounding tool is not used, the surface of the workpiece has insulation and the ground wire with severe aging for a long time will cause poor contact between the ground wire and the workpiece.

Special grounding tools should be used and checked for insulation that affects ground wire contact with the workpiece surface, avoiding the use of aged grounding wires.

6. Spark generator can not automatically break the arc

When the plasma cutting machine is working, the plasma arc is first ignited, and the gas between the electrode and the inner wall of the nozzle is excited by the high-frequency oscillator to generate a high-frequency discharge, so that the gas is locally ionized to form a small arc, which is compressed by the air. The action, which is ejected from the nozzle to ignite the arc, is the main task of the spark generator. Under normal circumstances, the working time of the spark generator is only 0.5 to 1 s. The reason why the arc cannot be automatically broken is generally to control the offset of the circuit board components, and the discharge electrode gap of the spark generator is not suitable.

Always check the spark generator discharge electrode to keep its surface flat, adjust the discharge electrode gap (0.8 ~ 1.2mm) of the spark generator in time, and replace the control board if necessary.

7. Other

In addition to the above reasons, the cutting speed is too slow, the perpendicularity of the torch and the workpiece during cutting, as well as the operator's familiarity with the plasma cutting machine, the operating level, etc., all affect the stability of the plasma arc, the user should pay attention to these aspects .

Ningxia Huahui Activated Carbon Company Limited (Huahui Company) was founded in 1992, its registered capital is 1.6912 billion yuan, production capacity is 35000 tons every year. With more than 20 years`experience in foreign trade, HuaHui Company is one of the key enterprises of foreign trade  in Ningxia Hui Autonomous Region.

The characteristics of the products in Huahui Company based on the developed micropores of Taixi Coal inherent, adjusting pore and making transition hole and large pore distribution extent according to customers` demands. 

Powder carbon is Huahui Company's third series of products. The common  produced varieties are 30x200mesh, 60x200mesh, 100x200mesh, <200mesh, <325mesh etc.

Powder activated carbon, which is grinded into suitable powder size with qualified activated carbon.Furnance. Because of its powder state, better diffusivity, it can full touch to the reaction material.  Meantime, it is applying to disposable recovery treatment of  filling water and industrial waste water with its high efficient adsorption, moreover, also used for refining and  decolorization of liquid. The types we manufacture through the year include HF-30x200, HF-60X200,HF-100X200,HF-325 etc.

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