The choice of cutting process parameters of CNC plasma cutting machine is very important to the impact of cutting quality, cutting speed and efficiency. In order to correctly use CNC plasma cutting machine for high-quality fast cutting, it is necessary to have a deep understanding and mastery of cutting process parameters.
1. Cutting current
It is the most important cutting process parameter, which directly determines the thickness and speed of cutting, that is, cutting ability. The larger the cutting current, the higher the cutting capacity, the higher 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 optimal cutting speed range can be selected according to the equipment instructions or determined by experiments. Due to the thickness of the material, different materials, melting point, thermal conductivity and surface tension after melting, the cutting speed also changes accordingly. The level of speed directly affects the cutting quality, higher and lower are not good.
3. Arc voltage
It is generally considered that the normal output voltage of the power supply is the cutting voltage. Plasma cutting machines usually have higher no-load voltage and working voltage. When the current is constant, the increase of the voltage means the increase of the arc enthalpy and the improvement of the cutting ability. If the diameter of the jet is reduced and the flow rate of the gas is increased while the enthalpy value is increased, a faster cutting speed and better cutting quality can often be obtained.
4.the nozzle height
Refers to the distance between the nozzle end face and the cutting surface, which forms part of the entire arc length. Since the arc cutting of CNC plasma cutting machine generally uses a power supply with constant current or abrupt drop characteristics, after the nozzle height increases, the current changes very little, but it will increase the arc length and cause the arc voltage to increase, thereby increasing the arc power; but at the same time It will also increase the arc length exposed to the environment, and the energy lost by the arc column will increase.
In the case of the combined effect 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 ability. Usually, the blowing force of the cutting jet is weakened, the slag remaining in the lower part of the incision increases, and the upper edge is over-melted and rounded corners appear.
5. Cutting power density
In order to obtain the plasma arc cutting arc with high compressibility, the cutting nozzle adopts smaller nozzle diameter, longer channel 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. increase. But at the same time, the compression also increases the power loss of the arc. Therefore, the actual effective energy used for cutting is smaller than the power output by the power supply, and the loss rate is generally between 25% and 50%. Some methods such as water compression plasma arc cutting The energy loss rate will be larger, which should be considered when the CNC plasma cutting machine performs the cutting process parameter design or the economic accounting of the cutting cost.
Increasing the compression degree of the arc can prolong the high-temperature plasma jet to form a more uniform high-temperature area, and at the same time increase the speed of the jet, which can reduce the width difference above and below the incision. However, the excessive compression of conventional nozzles often causes double arcing, which not only wears out the electrode and nozzle, making the cutting process impossible, but also leads to a decrease in the quality of the cut. In addition, too large cutting speed and too large nozzle height will cause the increase of the difference between the upper and lower width of the incision.
