How does a plasma cutter work?
Plasma cutters can be with different working gases to cut all metals that are difficult to cut by oxygen. It is important to note that non-ferrous metals (stainless steel, aluminum, copper, titanium, nickel) have better cutting results. Its advantage is that the cutting thickness for small metals, plasma cutting speed. When cutting ordinary carbon steel sheets, the speed can reach 5-6 times the oxygen cutting method. The cutting surface is bright, the heat deformation is small, and there is almost no thermal influence area. Plasma cutting machines are widely used in a variety of industries, such as automobiles, locomotives, pressure vessels, chemical machinery, nuclear industry, general machinery, construction machinery and steel structures.
Working principle and process 1. Compressed air is distributed by the gas chamber after entering the torch, forming plasma gas and auxiliary gas. Plasma arcs have the effect of melting metals, while auxiliary gases cool parts of the torch and blow away the molten metal. 2. Cutting off the power supply consists of two parts: the main circuit and the control circuit. Electrical principle: The main circuit consists of a contactor, a three-phase power transformer with high leakage resistance, a three-phase bridge rectifier, a high-frequency arc ignition coil and maintenance components.
Due to the high leakage resistance, the external characteristics of the power supply are steep. The control circuit completes the cutting process with a button switch on the torch: pre-exhaust-main circuit power supply-high-frequency arc ignition-cutting process-arc off-stop. The main circuit power supply is controlled by the contactor, the gas flow is controlled by the solenoid valve, the high frequency oscillator is controlled by the control circuit to ignite the arc, and the high frequency operation is stopped after the arc is established.
Various plasma arc cutting process parameters directly affect the stability, quality and effect of the cutting process. The main cut criteria are as follows: <>
1. The empty-load voltage and arc column voltage plasma cutting power supply need to have a high air-load voltage to make it easy to arc and make the plasma arc burn steadily. The empty-load voltage is typically 120-600V, and the arc column voltage is typically half the empty-load voltage. Increasing the voltage of the arc column can significantly increase the power of the plasma arc, thus increasing the cutting speed and cutting the larger thickness of the metal plate. By regulating the gas flow and increasing the internal shrinkage of the electrode, it is often impossible to reach the arc column voltage, but the arc column voltage must not exceed 65% of the empty voltage, otherwise the plasma arc will become unstable. <>
2. Cut-in current adding cut-in current can also increase the power of the plasma arc, but will be limited by the allowable current, otherwise it will thicken the plasma arc column, increase the gap width, and reduce the life of the electrode. <>
3. Increased air flow can not only improve the arc column voltage, but also improve the solidity effect of the arc column, so that the plasma arc energy is more concentrated, the eruption force is stronger, can improve the cutting effect. Speed and quality. However, if the gas flow is too large, the arc tower is shortened, heat is lost and the cutting capacity is reduced until the cutting process cannot be performed properly. <>
4. Electrode shrinkage so-called contraction refers to the distance between the electrode and the cutting nozzle end face. Proper spacing allows the arc to be compact in the cutting nozzle and obtains a plasma arc with concentrated energy and high temperature for useful cutting. If the interval is too large or too small, the electrode will burn severely, the cut mouth will burn out, and the cutting capacity will be reduced. The shrinkage is generally 8-11mm.
