1. Open-circuit voltage and arc voltage: A plasma cutting power source must have a sufficiently high open-circuit voltage to facilitate arc ignition and ensure stable plasma arc combustion. The open-circuit voltage is typically 120-600V, while the arc voltage is generally half of the open-circuit voltage. Increasing the arc voltage significantly increases the power of the plasma arc, thus increasing cutting speed and the ability to cut thicker metal sheets. The arc voltage can often be adjusted by regulating gas flow and increasing electrode indentation, but it should not exceed 65% of the open-circuit voltage; otherwise, the plasma arc will become unstable.
2. Cutting current: Increasing the cutting current also increases the power of the plasma arc, but it is limited by the maximum allowable current. Otherwise, the plasma arc column will thicken, the kerf width will increase, and electrode life will decrease.
3. Gas flow rate: Increasing the gas flow rate increases both the arc voltage and the compression effect on the arc column, resulting in more concentrated plasma arc energy and stronger jet force, thus improving cutting speed and quality. However, excessive gas flow will shorten the arc column, increase heat loss, and weaken cutting ability.
4. Electrode Retraction: Retraction refers to the distance from the electrode to the nozzle end face. A suitable distance allows for good arc compression within the nozzle, resulting in a concentrated, high-temperature plasma arc for effective cutting. Too large or too small a distance will cause severe electrode burn-out, nozzle damage, and reduced cutting ability. Retraction is generally 8-11 mm.
5. Nozzle Height: Nozzle height is the distance from the nozzle end face to the surface of the workpiece being cut. This distance is generally 4-10 mm. Like electrode retraction, a suitable distance is essential to fully utilize the cutting efficiency of the plasma arc; otherwise, cutting efficiency and quality will decrease, or the nozzle may burn out.
6. Cutting Speed: All the above factors directly affect the compression effect of the plasma arc, that is, the temperature and energy density of the plasma arc. The high temperature and high energy of the plasma arc determine the cutting speed; therefore, all the above factors are related to the cutting speed. To ensure cutting quality, cutting speed should be increased as much as possible. This not only improves productivity but also reduces deformation of the cut parts and the heat-affected zone of the kerf. Inappropriate cutting speed will have the opposite effect, increasing slag adhesion and reducing cutting quality.