What are the factors affecting plasma cutting accuracy?

What are the factors affecting plasma cutting (accuracy)?

In the actual use and operation of the CNC plasma cutting machine, due to the optional brand of plasma power supply for the machine, the power of the plasma power supply, the cutting power of the plasma power supply, the thickness of the consumables such as the electrode of the cutting nozzle and the thickness of the metal sheet, etc. Various plasma arc cutting process parameters directly affect the stability, cutting quality and effect of the cutting process. We summarized the main cutting specifications as follows:

1. No-load voltage and arc column voltage

The plasma cutting power supply must have a high enough no-load voltage to easily start the arc and make the plasma arc steadily burn. The no-load voltage is generally 120-600V, and the arc column voltage is generally half of the no-load voltage. Increasing the arc column voltage can significantly increase the power of the plasma arc, thereby increasing the cutting speed and cutting larger thickness metal plates. The arc column voltage is often not reached by adjusting the gas flow and increasing the electrode internal shrinkage, but the arc column voltage cannot exceed 65% of the no-load voltage, otherwise the plasma arc will be unstable.

2. Cutting current

Increasing the cutting current can also increase the power of the plasma arc, but it is limited by the maximum allowable current, otherwise the plasma arc column will become thicker, the slit width will increase, and the electrode life will decrease.

3． Gas flow

Increasing the gas flow rate can not only increase the arc column voltage, but also enhance the compression effect on the arc column, so that the plasma arc energy is more concentrated and the spray force is stronger, so the cutting speed and quality can be improved. However, if the gas flow is too large, the arc column will be shortened, the heat loss will increase, and the cutting ability will be weakened until the cutting process cannot be performed normally.

4． Electrode shrinkage

The so-called internal shrinkage refers to the distance from the electrode to the end face of the cutting tip. A suitable distance can make the arc well compressed in the cutting tip, obtain a plasma arc with high energy concentration and high temperature for effective cutting. If the distance is too large or too small, the electrode will be severely burned, the cutting tip will be burned, and the cutting ability will be reduced. The shrinkage is generally 8-11mm.

5. Nozzle height

The cutting nozzle height refers to the distance from the end of the cutting nozzle to the surface of the workpiece to be cut. The distance is generally 4 ~ 10mm. It is the same as the internal shrinkage of the electrode, and the distance must be appropriate to give full play to the cutting efficiency of the plasma arc, otherwise the cutting efficiency and cutting quality will be reduced or the cutting nozzle will be burned out.

6. Cutting speed

The above various factors directly affect the compression effect of the plasma arc, that is, the temperature and energy density of the plasma arc, and the high temperature and high energy of the plasma arc determine the cutting speed, so the above various factors are related to the cutting speed. On the premise of ensuring the cutting quality, the cutting speed should be increased as much as possible. This not only improves productivity, but also reduces the amount of deformation of the part being cut and the heat-affected zone of the slit area. If the cutting speed is not suitable, the effect will be reversed, and the sticky residue will increase and the cutting quality will decrease.