1. How to select the type of ionic gas in the plasma arc cutting process?
The type of ionic gas used determines the cut-off voltage. When current remains constant, higher voltage results in greater thickness and cutting speed. When cutting thick materials, it is more efficient to adjust the ionic gas composition to increase the cutting voltage rather than increase the current.
However, it is important to note that the arc may extinguish if the cut-off voltage exceeds 2/3 of the no-load voltage of the power supply. To avoid this, the no-load voltage of the power supply must be at least twice the arc voltage.
The most commonly used ionic gas for cutting is nitrogen, with an arc voltage of 150 to 200V. Other ionic gas mixtures include nitrogen-argon (arc voltage 120 to 200 V), nitrogen-hydrogen (arc voltage 180 to 300 V), and argon-hydrogen (arc voltage 150 to 300 V). The air arc voltage is normally 110 to 150V.
Due to its low cost and availability, air is widely used for cutting various materials.
two . C Compared with plasma arc welding gun, what are the characteristics of plasma arc cutting gun?
The design of a plasma arc cutting gun is similar to that of a plasma arc welding gun. However, there are some important differences between the two.
One of the main differences is the nozzle channel aspect ratio. The nozzle of a cutting gun has a much larger channel ratio compared to that of a welding gun. This design allows a higher velocity ionized gas flame to flow from the nozzle during cutting, which helps melt the base metal and blow away the molten metal to create a cut.
Due to the strong cooling effect of high-velocity ionized gas, the nozzle of a cutting gun does not require water cooling. However, it is common for the cutting gun itself to be cooled with water.
3. What are the advantages and disadvantages of plasma arc cutting compared to oxyacetylene flame and mechanical cutting?
Plasma arc cutting has several advantages over mechanical cutting, including the ability to cut thicker materials, greater flexibility in cutting patterns, and a simplified process for clamping the workpiece. Additionally, plasma arc cutting uses concentrated energy to minimize deformation and there is no need for preheating before cutting.
However, plasma cutting also has some disadvantages. It is less precise than mechanical cutting and can produce dangerous byproducts such as arc radiation, smoke and noise during the cutting process. Furthermore, plasma arc cutting equipment is more expensive than oxyacetylene flame cutting equipment.
4. What is air plasma arc cutting? What are the characteristics of air plasma arc cutting?
Air plasma arc cutting is a cutting method that uses compressed air as an ionic gas to generate heat through arc ionization. This results in high enthalpy plasma under the influence of an electric field, which produces large arc energy and high cutting speed.
This method is versatile and can be used to cut a variety of materials, including non-ferrous metals such as aluminum alloys, as well as stainless steel and carbon steel. Additionally, air plasma arc cutting is economical and has a readily available gas source. Currently, it is the most used cutting method in China.
5. What equipment is needed for manual air plasma arc cutting?
The air plasma arc cutting system consists of three main components: the gas supply unit, the DC power supply and the cutting gun.
The gas supply unit is equipped with a 1.5 to 2.2 kW air compressor and requires a gas pressure of 0.3 to 0.6 MPa for cutting. The DC power supply has a sharp voltage drop or slow voltage drop characteristic.
The gas source supplies ionic gas to the cutting gun, which requires a high flow rate. As a result, the outlet pressure of the gas source used for cutting is significantly higher than that of the gas source used for welding.
6. How to select air plasma arc equipment?
Air plasma arc cutting equipment mainly consists of a gas circuit, a DC current source and a cutting gun.
The equipment is classified according to its current capacity, and the user must select the cutting machine appropriate to their needs based on the thickness of the material to be cut. The manufacturer provides guidance on recommended cutting thickness in the product manual, but it is possible to exceed these limits.
It is important to note that as the cutting thickness increases, the cutting speed decreases. This decrease in cutting speed not only reduces production efficiency but also affects cutting quality. Problems such as wider cutting seams, slag hanging on the back of the material and other quality problems may arise.
From the point of view of improving cutting quality, it is generally better to have a faster cutting speed, as long as cutting penetration is still guaranteed.
7. Do cutting machines with the same current class have the same cutting thickness?
The relationship between cutting thickness and current is not determined by current alone. Shear stress also plays a significant role.
The cutting voltage is mainly determined by the cutting gun and cutting gas flow. Currently, there are numerous manufacturers that produce cutting machines, and each may use different cutting guns and gas circuits, even when producing machines with the same current level. This results in varying cutting stresses.
When the current is constant, the cutoff voltage and thickness are positively correlated; higher cutting voltage results in greater kerf thickness. However, factory instructions typically only provide the no-load voltage, not the cut-off voltage. The cut-off voltage for air plasma arc cutting machines with a current range of 30 to 100A is normally between 110 to 150V.
