Features and precautions of the hottest plasma cut

2022-08-26
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Features and precautions of plasma cutting machine

plasma cutting machine can cut all kinds of metals that are difficult to be cut by oxygen with different working gases, especially for non-ferrous metals (stainless steel, aluminum, copper, titanium, nickel); Its main advantage is that when cutting metal with small thickness, the plasma cutting speed is fast, especially when cutting ordinary carbon steel sheet, the speed can reach times of oxygen cutting method, the cutting surface is smooth, the thermal deformation is small, there is almost no unloading and the piston of the experimental machine falls back to the original position of the heat affected zone

with the development of plasma cutting machine, the working gas that can be used (the working gas is the conductive medium of the plasma arc, the heat carrier, and the molten metal in the notch at the same time) has a significant impact on the cutting characteristics, cutting quality and quality of the plasma arc. The commonly used plasma arc working gases are argon, hydrogen, nitrogen, oxygen, air, water vapor and some mixed gases

II. Precautions for plasma cutting machine

the selection of process parameters of CNC plasma cutting machine is crucial to the cutting effect such as cutting quality, cutting speed and efficiency. It is necessary to have a deep understanding and mastery of cutting process parameters to correctly use CNC plasma cutting machine for high-quality rapid cutting

(I): cutting current: it is the most important cutting process parameter, which directly determines the thickness and speed of cutting, that is, the cutting ability. Effects: 1. The cutting current increases, the arc energy increases, the cutting capacity increases, and the cutting speed increases accordingly; 2. With the increase of cutting current, the machine head is divided into oblique angle (120 degrees) and right angle (90 degrees). The arc diameter of the machine head increases, and the arc thickens, making the cutting wider; 3. If the cutting current is too high, the nozzle heat load will increase, the nozzle will be damaged prematurely, and the cutting quality will naturally decline, or even normal cutting will not be possible. Therefore, the cutting current and the corresponding nozzle should be correctly selected according to the thickness of the material before cutting

(II). Cutting speed: the optimal cutting speed range can be selected according to the equipment description or determined by the high impact resistance test of solid and hard materials. Due to the thickness of materials, different materials, high and low melting point, thermal conductivity and surface tension after melting, the cutting speed also changes the same. Main manifestations: 1. Moderately improving the cutting speed can improve the quality of the incision, that is, the incision is slightly narrower, the surface of the incision is smoother, and the deformation can be reduced at the same time. 2. The cutting speed is too fast, which makes the cutting linear energy lower than the required value. The jet in the cutting seam cannot quickly blow off the molten cutting melt immediately, resulting in a large amount of drag. With the slag hanging on the incision, the surface quality of the incision decreases. 3. When the cutting speed is too low, because the cutting place is the anode of the plasma arc, in order to maintain the stability of the arc itself, the anode spot or anode area must find the place of conducting current near the slit nearest to the arc, and at the same time, it will transfer more heat to the radial direction of the jet. Therefore, the incision is widened, and the molten materials on both sides of the incision gather and solidify at the bottom edge, forming slag that is not easy to clean, Moreover, the upper edge of the incision forms a fillet due to excessive heating and melting. 4. When the speed is very low, the arc will even go out because the notch is too wide. It can be seen that good cutting quality and cutting speed are inseparable

(III). Arc voltage: it is generally considered that the normal output voltage of the power supply is the voltage. Plasma arc cutting machines usually have high no-load voltage and working voltage. When using gases with high ionization energy such as nitrogen, hydrogen or air, the voltage required to stabilize the plasma arc will be higher. When the current is constant, the increase of voltage means the increase of arc enthalpy. At the same time, reducing the diameter of jet and increasing the flow rate of gas can often obtain faster cutting speed and better cutting quality

(IV). Working gas and flow: working gas includes cutting gas and auxiliary gas. Some equipment also requires arc starting gas. Usually, the appropriate working gas should be selected according to the type, thickness and cutting method of cutting material. Cutting gas should not only ensure the formation of plasma jet, but also ensure the removal of molten metal and oxide in the incision. Excessive gas flow will take away more arc heat, making the length of the jet shorter, leading to the decline of cutting ability and instability of the arc; Too small air flow will make the plasma arc lose its due straightness and make the cutting thickness shallow, and it is also easy to produce slag; Therefore, the gas flow must be well matched with the cutting current and speed. Nowadays, most plasma arc cutting machines rely on gas pressure to control the flow, because when the gun aperture is fixed by a capacitive displacement sensor, the gas pressure controls the flow, and the gas pressure needs to be determined through actual cutting experiments. The most commonly used working gases are argon, nitrogen, oxygen, air, H35, argon nitrogen mixture, etc

source: Fuzhou Bolima Precision Machinery Co., Ltd

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