Maintenance of CNC Metal Plasma Cutting

The plasma cutting process is a thermal cutting method. Which means that is uses heat to melt the metal instead of mechanically cutting it.cnc metal plasma cutting is a process that cuts through the electrically conductive material with the help of hot plasma. Plasma cutting machines use a high-velocity jet of ionized gas that is delivered from the orifice. Plasma conducts electricity from the torch of the plasma cutter to the workpiece and heats the object, thereby melting the material. The high-velocity stream of ionized gas mechanically blows the molten metal away, splitting the materials.

The main circuit includes contactor, high leakage resistance of the three-phase power transformer, three-phase bridge rectifier, high-frequency arc coil and protective components, etc., the main circuit includes the main circuit and control circuit, composition.Plasma Cutting Machine

By the high leakage resistance to steep the power of the external characteristics. The control circuit completes the entire cutting process through the pushbutton switch on the torch: pre-venting – main circuit power supply – high frequency lead-cutting process – arc – stop. The main circuit of the power supply by the contactor control; gas short by the solenoid valve control; by the control circuit to control the high-frequency oscillator ignition arc, and after the establishment of the arc to stop the high frequency.

installing or replacing the torch parts, move the torch head up and press the protective cover – the conductive nozzle – the gas distributor – the electrode – the torch body in the reverse order; in reverse order assembly. When installing the nozzle, keep the concentricity with the electrode. Protective cover to be tightened, the nozzle to be pressed, if loose, can not cut. Reasonable use of the torch, the nozzle and the workpiece in contact with the arc; and cutting the end, you should first release the handle button off the arc, and then remove the torch from the workpiece surface, which can extend the life of parts. When the nozzle due to the central empty and affect the quality of cutting should be promptly replaced. When the center of the electrode is more than 2 mm deep or can not be arcned, the electrode can be used in reverse or in use.Plasma Cutting Machine

Operation

CNC metal plasma cutting processes rely on a jet of ionized gas that melts and severs a material. The gas is heated to a temperature of over 20,000° C and an electric arc forms between an electrode and the workpiece. The electrode is positioned in a gas nozzle cooled by water or air, which constricts the arc forming a narrow, high-velocity, high-temperature stream of plasma.

When the plasma jet strikes the workpiece, it transfers intense heat due to ion recombination, causing the gas to return to its normal state. The heat melts the metal material, and the stream of gas blows the molten material away through the cut. During this process, the surface around the cutting area remains cool. Standard gases used in plasma cutting include argon, nitrogen, hydrogen, or an argon/hydrogen combination. Integration of compressed air makes the plasma method more competitive to oxy-fuel cutting of carbon-manganese and stainless steels. Whereas, inert gasses are effective for high-quality cutting of reactive alloys.

As the plasma device moves along the surface, it produces a clean, linear cut with little minimal slag or dross. The width of the melted zone can be less than 1/16″ (1.6mm). Temperatures generated during the process reach up to 16,600° C. Piercing the metal at an acute angle of approximately 60 degrees produces the best results. An excessive amperage or inadequate gas flow can cause the formation of a double arc, leading to a significant reduction in nozzle life.

How to select a cnc metal plasma cutting?

plasma cutting marine applicationThe following needs consideration when selecting a plasma cutter:

Manual or mechanised ?

Are you looking to cut by hand or use a CNC machine? – consider the availability of CNC interface signals and voltage divider (to provide safe voltage levels from the torch to control the height of the torch automatically).

1. Required Cut thicknesses and quality
2. Material thickness needs to be matched with the capabilities of the plasma cutter. The cutting capabilities are specified as thickness limits by the manufacturers as follows:
3. Sever cut – just capable of cutting this thickness with dross and slag left behind
4. Rated cut – this is the rated cut thickness specified by the manufacturer of the plasma cutter
5. Quality cut – a quality cut is achieved for materials up to this thickness
6. Kerf (cut width) – higher quality plasma cutting systems can make narrower cuts
7. Duty cycle

How does plasma cutting compare to oxyfuel cutting?

Plasma cutting can be performed on any type of conductive metal – mild steel, aluminum and stainless are some examples. With mild steel, operators will experience faster, thicker cuts than with alloys.Oxyfuel cuts by burning, or oxidizing, the base metal. It’s limited to steel and other ferrous metals that support the oxidizing process. Metals like aluminum and stainless steel form an oxide that inhibits further oxidization, making conventional oxyfuel cutting impossible. Plasma cutting, however, does not rely on oxidation to work, and thus it can cut aluminum, stainless and any other conductive material.While different gasses can be used for plasma cutting, most people today use compressed air for the plasma gas. In most operations, compressed air is readily available, and thus plasma does not require fuel gas and compressed oxygen for operation. Some portable units also supply air from an on-board compressor.Plasma cutting is typically easier for the novice to master, and on thinner materials, plasma cutting is much faster than oxyfuel cutting. However, for heavy sections of steel (1 inch and greater), oxyfuel is still preferred since oxyfuel is typically faster and requires lower capacity power supplies than plasma.