CNC plasma cutting machine skills and cutting knowledge


The CNC plasma cutting machine is combined with a simple and easy-to-use CNC system to ionize the high-speed airflow ejected from the nozzle at high temperature to form a conductor. When the current passes, the conductor forms a high-temperature plasma arc. The heat of the arc partially melts (and evaporates) the metal at the incision of the workpiece, and uses the power of the high-speed plasma airflow to remove the molten metal to form a processing method. The slender and stable plasma arc formed by circular airflow technology ensures smooth and economical cutting of any conductive metal.

When using the CNC plasma cutting machine, its cutting quality is unstable, and the wearing parts are replaced frequently. It is found that the users are not standardized enough to use the CNC plasma cutting machine during operation, and at the same time, they do not pay enough attention to some detailed problems. Below we Summarized some tips for daily use of CNC plasma cutting machines, hoping to bring you convenience

 

1. Cutting should start from the edge

Whenever possible, start cutting from the edge rather than piercing the cut. Using the edge as the starting point will extend the life of the consumable, and the correct way to start the plasma arc is to align the nozzle directly at the edge of the workpiece.

2. Reduce unnecessary "arcing (or arcing)" time

Both the nozzle and the electrode are consumed very quickly when starting the arc, and the torch should be within walking distance of the cutting metal before starting.

3. Do not overload the nozzle

Overloading the nozzle (that is, exceeding the operating current of the nozzle) will quickly damage the nozzle. The current intensity should be 95% of the working current of the nozzle. For example: the current intensity of a 100A nozzle should be set to 95A.

4. Use a reasonable cutting distance

According to the requirements of the instruction manual, use a reasonable cutting distance, which is the distance between the cutting nozzle and the surface of the workpiece. When piercing, try to use twice the normal cutting distance or the maximum height that can be transmitted by the plasma arc.

5. The perforation thickness should be within the allowable range of the machine system

The cutting machine cannot perforate the steel plate exceeding the working thickness, the usual perforation thickness is 1/2 of the normal cutting thickness, try to keep the torch and consumables clean, any dirt on the torch and consumables will greatly affect the plasma system functionality. When replacing consumables, put them on a clean velvet cloth, check the connecting thread of the torch frequently, and clean the electrode contact surface and nozzle with hydrogen peroxide cleaner.

The cutting speed of CNC plasma cutting machine has different effects on cutting quality


The combination of CNC cutting machine and plasma power supply is called CNC plasma cutting machine. It is easy to produce cracks in plasma cutting. There are many reasons for cracks. Usually, the best cutting speed range of plasma CNC cutting machine can be selected according to the equipment instructions. Or use experiments to determine, but due to the thickness of the workpiece to be cut, the different materials, the melting point, the thermal conductivity, and the surface tension after melting, the cutting speed of the plasma CNC cutting machine also changes accordingly. Its main performance is as follows:


1. When the cutting speed of the plasma CNC cutting machine is moderately increased, the quality of the incision can be improved, that is, the incision is slightly narrowed, the surface of the incision is smoother, and the deformation can be reduced at the same time.


2. When the cutting speed of the plasma CNC cutting machine is too fast, the cutting line energy is lower than the required value, and the jet in the slit cannot quickly blow off the molten cutting melt immediately, resulting in a large amount of back drag, accompanied by With the slag hanging on the incision, the surface quality of the incision decreases.


3. When the cutting speed of the plasma CNC cutting machine is too low, since 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 a conduction place near the slit closest to the arc. At the same time, more heat will be transferred to the radial direction of the jet, so the incision will be widened, and the molten material on both sides of the incision will gather and solidify at the bottom edge, forming hanging slag that is not easy to clean, and the upper edge of the incision is formed due to excessive heating and melting rounded corners.


4. When the cutting speed of the plasma CNC cutting machine is extremely low, the arc will even go out because the cut is too wide. It can be seen that good cutting quality is inseparable from cutting speed.

Selection skills and key points of CNC plasma cutting machine gas


CNC plasma cutting machines usually have higher 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 and cutting ability. If the diameter of the jet is reduced and the flow rate of the gas is increased while the enthalpy is increased, a faster cutting speed and better cutting quality can often be obtained.


1. Hydrogen is usually mixed with other gases as an auxiliary gas. For example, the famous gas H35 (the volume fraction of hydrogen is 35%, and the rest is argon) is one of the gases with the strongest plasma arc cutting ability, which is mainly due to hydrogen. Since hydrogen can significantly increase the arc voltage, the hydrogen plasma jet has a high enthalpy value. When mixed with argon, the cutting ability of the plasma jet is greatly improved.


2. Oxygen can increase the speed of cutting low carbon steel materials. When using oxygen for cutting, the cutting mode is very similar to that of the CNC flame cutting machine. The high-temperature and high-energy plasma arc makes the cutting speed faster, but the spiral duct machine must be used in conjunction with high-temperature oxidation-resistant electrodes. Shock protection to prolong electrode life.


3. The air contains nitrogen with a volume fraction of about 78%, so the slag formed by cutting with air is very similar to that of cutting with nitrogen; the air also contains oxygen with a volume fraction of about 21%, because of the existence of oxygen, using air The cutting speed of low carbon steel materials is also very high; at the same time, air is also the most economical working gas. However, when air cutting is used alone, there will be problems such as slag hanging, incision oxidation, and nitrogen increase, and the low life of electrodes and nozzles will also affect work efficiency and cutting costs. Since plasma arc cutting generally uses a power supply with constant current or steep drop characteristics, the current changes little after the nozzle height increases, but it will increase the arc length and cause the arc voltage to increase, thereby increasing the arc power; but at the same time As the arc length exposed to the environment increases, the energy lost by the arc column increases.


4. Nitrogen is a commonly used working gas. Under the condition of higher power supply voltage, the nitrogen plasma arc has better stability and higher jet energy than argon, even for cutting liquid metal with high viscosity materials such as For stainless steel and nickel-based alloys, the amount of slag hanging on the lower edge of the cut is also very small. Nitrogen can be used alone or mixed with other gases to use the plasma cutting machine. For example, nitrogen or air is often used as the working gas in automatic cutting. These two gases have become the standard gas for high-speed cutting of carbon steel. Nitrogen is also sometimes used as the starting gas for oxygen plasma arc cutting.


5. Argon hardly reacts with any metal at high temperature, and the argon CNC plasma cutting machine is very stable. Moreover, the used nozzles and electrodes have a relatively high service life. However, the voltage of the argon plasma arc is low, the enthalpy is not high, and the cutting capacity is limited. Compared with the air cutting, the cutting thickness will be reduced by about 25%. In addition, in the argon gas protection environment, the surface tension of the molten metal is relatively high. , which is about 30% higher than that in a nitrogen environment, so there will be more slag problems. Even cutting with a mixture of argon and other gases tends to stick to the dross. Therefore, pure argon is rarely used alone for plasma cutting. The use and selection of gas is very important when CNC plasma cutting machine is cutting. The use of gas will seriously affect the cutting accuracy, slag hanging and other phenomena.


Application range of air-cooled cutting torch for CNC plasma cutting machine
The air-cooled torch of CNC plasma cutting machine refers to the plasma cutting torch cooled by air, which is mainly concentrated in the plasma power supply within 100A. Generally, the commonly used CNC plasma cutting machine is equipped with different types of cutting torches according to the thickness of the cutting plate. Here we The air-cooled CNC plasma cutting torch mentioned is mainly different from the water-cooled torch. It is generally suitable for cutting and processing metal materials such as stainless steel and carbon plates below 10MM. The air-cooled torch is also called air-cooled torch. The torch, in short, is to reduce the surface temperature of the torch through the natural cooling of the air to achieve the purpose of long-term use. Air-cooled cutting torches have a shorter service life due to different cooling methods.


1. If the hafnium wire in the center of the electrode in the cutting torch is burned by 2.5--3mm, it should be replaced in time. The electrode must be completely cooled (blow with compressed air) when replacing, otherwise the electrode base will become greasy due to thermal expansion. Do not use too much force when unscrewing, otherwise the electrode base may be easily damaged. Before replacing electrodes and nozzles, it is necessary to check whether the inner cavity is clean, and impurities must be removed before use.


2. During normal use, if you suddenly hear a "scaring" sound, the arc light is red, and the arc ballast is running up, you should stop using it immediately. At this time, the electrode and nozzle are damaged. If you continue to use it forcibly, it will damage the torch. Can be used behind the nozzle.


3. The operating current of the air-cooled cutting torch should not be greater than its rated current, otherwise the torch will be easily damaged.


4. When replacing electrodes and nozzles, the power of the main engine must be turned off. When the cutting torch is not equipped with electrodes and nozzles, the torch switch cannot be pressed.


5. The compressed air used must be dry and clean. Because moisture and oil are easy to conduct electricity, spiral black lines appear on the electrode, which means that too much moisture and oil will short-circuit the electrode and the inner cavity of the nozzle, easily damage the cutting torch, and fail to work normally.


6. The electrode and nozzle in the cutting torch cannot be loosened during use. The electrode must be tightened with a special wrench. It must be checked before each use. If there is any looseness, tighten it with a special wrench at any time, but do not use an adjustable wrench or the like. tool.


Cutting current selection of CNC plasma cutting machine


When correctly using the CNC plasma cutting machine for high-quality fast cutting, it is necessary to deeply understand and master the cutting process parameters. For the best effect, the following Bangke CNC will explain to you the cutting current adjustment parameters of the plasma CNC cutting machine when cutting workpieces, for reference and learning by the majority of users. When the plasma CNC cutting machine cuts the workpiece, the cutting current regulation of the machine plasma power supply is very important. It is the most important cutting process parameter, which directly determines the cutting thickness and speed, that is, the cutting capacity. Regarding the impact, it is directly manifested in the following points in the selection form of the cutting current of the plasma CNC cutting machine:


1. As the cutting current of the plasma CNC cutting machine increases, the energy of the plasma arc increases, the cutting ability increases, and the cutting speed increases accordingly;


2. The cutting current of the plasma CNC cutting machine increases, the diameter of the plasma arc increases, and the thickening of the arc makes the incision wider;


3. If the cutting current of the plasma CNC cutting machine is too large, the thermal load of the nozzle will increase, the nozzle will be damaged prematurely, the cutting quality will naturally decline, and even normal cutting cannot be performed. Therefore, the cutting current and the corresponding nozzle should be correctly selected according to the thickness of the material before cutting.