Typical case analysis of arc instability fault of plasma cutting machine

Typical case analysis of arc instability fault of plasma cutting machine

The stability of the plasma cutter arc directly affects the cutting quality. The instability of the plasma arc will lead to defects such as uneven incision and accumulation, and will also lead to a reduction in the life of the related components of the control system, and frequent replacement of nozzles and electrodes. In view of this phenomenon, analyze and propose solutions:

1. air pressure too low

When the plasma cutting machine is working, if the working air pressure is far lower than the air pressure required by the manual, it means that the ejection 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. , resulting in poor incision quality, incision, and incision accumulation. The reasons for insufficient air pressure are: insufficient input air from the air compressor, too low pressure regulation of the air regulating valve of the cutting machine, oil pollution in the solenoid valve, and unobstructed air passage.

Solution: Pay attention to the output pressure display of the air compressor before use. If it does not meet the requirements, you can adjust the pressure or repair the air compressor. If the input air pressure has reached the requirements, check whether the adjustment of the air filter pressure reducing valve is correct; the gauge pressure display can meet the cutting requirements. Otherwise, routine maintenance should be performed on the air filter pressure reducing valve to ensure that the input air is dry and free of oil. If the input air quality is poor, it will cause oil pollution in the pressure reducing valve, the valve core is difficult to open, and the valve port cannot be fully opened. In addition, if the air pressure of the torch nozzle is too low, it is necessary to replace the pressure reducing valve; if the gas path section becomes smaller, the air pressure will also 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 far exceeds 0.8MPa, after the formation of the ion arc, the excessive airflow will blow away the concentrated arc column, disperse the energy of the arc column, and weaken the cutting strength of the plasma arc. The reasons for the high air pressure are: improper adjustment of the input air, excessive adjustment of the air filter pressure reducing valve or failure of the air filter pressure reducing valve

The solution is to check whether the pressure of the air compressor is properly adjusted, and whether the pressure of the air compressor and the air filter pressure reducing valve is out of balance. After turning on the machine, if the air filter pressure reducing valve is turned to adjust the switch, the gauge pressure does not change, indicating that the air filter pressure reducing valve is out of order and needs to be replaced.

3. Torch nozzle and electrode burnout

Improper installation of the nozzle, such as the thread is not tightened, the gears of the equipment are not adjusted properly, the cutting torch that needs to be cooled by water does not pass the flowing cooling water as required and frequent arcing will cause the nozzle to be damaged prematurely.

Solution: According to the technical requirements of the cutting workpiece, correctly adjust the gears of the equipment, check whether the torch nozzle is installed firmly, and the cooling water should be circulated in advance for the nozzle that needs to pass the cooling water. 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 plasma cutting machine has large-scale power facilities, and the main circuit components of the cutting machine are faulty, etc., which will make the input AC voltage too low. Solution: Check whether the power grid connected to the plasma cutting machine has sufficient carrying capacity and whether the specifications of the power cord meet the requirements. The installation location of the plasma cutting machine should be far away from large electrical equipment and places with frequent electrical interference. During use, regularly clean the dust in the cutting machine and the dirt on the components, and check whether the wires are aging.

5. Poor contact between ground wire and workpiece

Grounding is an essential preparation before cutting. If no special grounding tool is used, there is insulation on the surface of the workpiece, and long-term use of the ground wire with serious aging will cause poor contact between the ground wire and the workpiece.

Solution: Special grounding tools should be used, and check whether there is any insulation that affects the contact between the ground wire and the surface of the workpiece, and avoid using an aging ground wire.

6. The spark generator cannot automatically cut off the arc

When the plasma cutting machine is working, the plasma arc must be ignited first, 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, which ionizes the gas locally to form a small arc, which is affected by the compressed air. It is sprayed from the nozzle to ignite the plasma arc, which is the main task of the spark generator. Under normal circumstances, the working time of the spark generator is only 85ms. The reason why the arc cannot be automatically interrupted is generally that the control circuit board components are out of tune, and the discharge electrode gap of the spark generator is not suitable.

Solution: Check the discharge electrode of the spark generator frequently to keep its surface flat, adjust the discharge electrode gap (1.6+0.05mm) of the spark generator in time, and replace the control board if necessary.

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