Correct way to use the CNC plasma cutting machine.
The selection of cutting process parameters of CNC plasma cutting machine is very important to cutting quality, cutting speed and efficiency. In order to correctly use the CNC plasma cutting machine for high-quality rapid cutting, we must deeply understand and master the cutting process parameters.
1、 Cutting current
It is the most important cutting process parameter, which directly determines the cutting thickness and speed, that is, the cutting capacity. The larger the cutting current, the higher the cutting capacity, the faster the cutting speed, the wider the cutting opening, the faster the damage speed of the cutting nozzle and the higher the cost. Therefore, the cutting current should be correctly selected according to the thickness of the material before cutting.
2、 Cutting speed
The best cutting speed range can be selected according to the equipment description or determined by test. Due to the thickness of the material, different materials, high and low melting point, thermal conductivity and surface tension after melting, the cutting speed also changes accordingly. The speed directly affects the cutting quality. The higher and lower the speed, the worse.
3、 Arc voltage
It is generally considered that the normal output voltage of the power supply is the cutting voltage. Plasma cutting machine usually has high no-load voltage and working voltage. When the current is constant, the increase of voltage means the increase of arc enthalpy and cutting ability. If we increase the enthalpy, reduce the diameter of the jet and increase the gas flow rate, we can often obtain faster cutting speed and better cutting quality.
4、 Nozzle height
It refers to the distance between the nozzle end face and the cutting surface, which constitutes a part of the entire arc length. Because CNC plasma cutting machine generally uses constant current or steep drop external power supply for arc cutting, the current changes little after the nozzle height increases, but it will increase the arc length and lead to the increase of arc voltage, so as to improve the arc power; But at the same time, the arc length exposed to the environment will increase, and the energy loss of arc column will increase.
In the case of the combined action of the two factors, the effect of the former is often completely offset by the latter, which will reduce the effective cutting energy and reduce the cutting capacity. It usually shows that the blowing force of the cutting jet is weakened, the residual slag at the lower part of the notch is increased, and the upper edge is over melted and rounded.
5、 Cutting power density
In order to obtain high-pressure plasma arc cutting arc, the cutting nozzle adopts smaller nozzle aperture, longer hole length and enhanced cooling effect, which can increase the current passing through the effective section of the nozzle, that is, the power density of the arc. But at the same time, compression also increases the power loss of the arc. Therefore, the effective energy actually used for cutting is smaller than the power output, and its loss rate is generally between 25%-50%. Some methods, such as water compression plasma arc cutting, will have a greater energy loss rate. This problem should be considered in the design of cutting process parameters or the economic accounting of cutting costs for CNC and other ion cutting machines.
Increasing the compression degree of the arc can lengthen the high-temperature plasma jet and form a more uniform high-temperature area. At the same time, increasing the jet speed can reduce the width difference between the upper and lower notches. However, the over compression of the conventional nozzle often causes the double arc phenomenon. The double arc will not only lose the electrode and nozzle, making the cutting process impossible, but also lead to the decline of the cutting quality. In addition, too high cutting speed and too high nozzle height will increase the width difference between the upper and lower notches.