When cutting with a CNC plasma cutting machine , special attention should be paid to the problem of plasma cutting arc. The instability of the arc of the CNC plasma cutting machine directly affects the cutting quality. The unstable phenomenon of the plasma arc will cause defects such as uneven cuts and accumulation of nodules, and will also reduce the life of related components of the control system. Frequent replacement of nozzles and electrodes . So what exactly makes the arc unstable?
1. Poor contact between ground wire and workpiece. Grounding is an essential preparation before cutting. Without using special grounding tools, insulation on the surface of the workpiece and long-term aging ground wire will make the ground wire contact the workpiece poorly. Special grounding tools should be used, and check whether there is insulation affecting the ground wire contact with the surface of the workpiece, avoid using aged ground wire.
2. The input AC voltage is too low. There is a large-scale electricity installation on the site of the plasma cutting machine. The failure of the main return components inside the cutting machine will cause the input AC voltage to be too low.
Solution: Check whether the network involved in the plasma cutting machine has sufficient carrying capacity and whether the power cord specifications meet the requirements. Plasma cutting machine should be installed away from large electrical equipment and places with frequent electrical interference. During use, regularly clean the dust and dirt on the components in the cutting machine, and check the wires for aging.
3. The air pressure is too low. When the plasma cutting machine is working, if the working air pressure is far lower than the air pressure required in the manual, 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, high energy and high High-speed plasma arc, resulting in poor incision quality, impervious cuts, and incision accumulation. The reasons for the insufficient air pressure include insufficient input air from the air compressor, too low pressure adjustment of the air regulator valve of the cutting machine, oil contamination inside the solenoid valve, and unsmooth air passages.
Solution: Observe the output pressure display of the air compressor before use. If it does not meet the requirements, it can be adjusted.
4. The spark generator cannot automatically cut off the arc. When the plasma cutting machine is working, the plasma arc must be ignited. The high-frequency oscillator excites the gas between the electrode and the inner wall of the nozzle to generate a high-frequency discharge, which locally ionizes the gas and forms a small gas. The arc, a small arc hand compressed air, is ejected 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 0.5-1s. The reason why the arc cannot be automatically interrupted is generally that the control circuit board components are out of adjustment, and the spark electrode discharge electrode gap is not suitable.
5. 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 air flow will disperse the concentrated arc column, dispersing the energy of the arc column, and weakening the cutting strength of the plasma arc. The causes of high air pressure are: improper adjustment of input air, excessive adjustment of air filter pressure reducing valve, or failure of air filter pressure reducing.
Solution: Check whether the air compressor is properly adjusted and whether the pressure of the air compressor and the air filter pressure reducing valve is out of adjustment. After turning on, if the adjustment switch of the air filter pressure reducing valve is turned on, there is no change, indicating that the air filter pressure reducing valve has failed and needs to be replaced. Pressure or overhaul air compressor. If the input air pressure has reached the requirements, you should check whether the adjustment of the air filter pressure reducing valve is correct, and the gauge pressure shows whether it can meet the cutting requirements. Otherwise, daily maintenance should be performed on the air filter pressure reducing valve to ensure that the input air is dry and dirty. If the input air quality is poor, it will cause oil pollution in the solenoid valve, it will be difficult to open the valve core, and the valve port cannot be completely opened. Also. The pressure of the cutting nozzle is too low, and the solenoid valve needs to be replaced; the smaller the cross section of the gas path will cause the pressure to be too low, you can replace the air pipe according to the instructions.
6. The cutting nozzle and electrode are burned. Due to improper installation of the nozzle, such as the screw is not tightened tightly, the cutting position of the equipment is not adjusted properly. The cutting torque that needs to be cooled by water does not pass in the flowing cooling water as required during operation. Arcing can cause premature nozzle damage.
Solution: According to the technical requirements of cutting the workpiece, adjust the gears of the equipment correctly, check whether the cutting nozzle is installed firmly, and the nozzle that needs to pass the cooling water should circulate the cooling water in advance. When cutting, adjust the distance between the cutting moment and the workpiece according to the thickness of the workpiece. The discharge electrode of the spark generator should be checked frequently to keep the surface flat. Adjust the discharge electrode gap (0.8-1.2mm) of the spark generator in a timely manner, and replace the control board if necessary.
7. In addition to the above reasons, the cutting speed is too slow, the cutting moment and the perpendicularity of the workpiece when cutting, and the operator's familiarity with the CNC plasma cutting machine, the level of operation, etc., all affect the stability of the plasma arc, users should be in Pay attention to these aspects.