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The choice of cutting parameters of the CNC plasma cutting machine is crucial for the cutting quality, cutting speed and efficiency. The correct use of CNC plasma machines for high-quality, rapid cutting requires a deep understanding and mastery of the cutting process parameters.
First, the cutting current: It is the most important cutting process parameters, directly determines the cutting thickness and speed, the cutting ability. Influencing: 1. Increased cutting current, increased arc energy, increased cutting capacity, increased cutting speed, 2. Increased cutting current, increased arc diameter, thicker arc, wider incision, 3. Cutting current As a result, the thermal load of the nozzle increases, the nozzle is damaged prematurely, and the cutting quality naturally decreases, and even normal cutting cannot be performed. Therefore, the cutting current and the corresponding nozzle should be selected correctly according to the thickness of the material before cutting.
Second, the cutting speed: The best cutting speed range can be selected according to equipment instructions or determined by tests, due to the thickness of the material, different materials, high and low melting point, thermal conductivity and surface tension after melting and other factors, cutting speed Corresponding changes. The main performances are as follows: 1. Moderately improved cutting speed can improve the quality of the incision, that is, the incision is slightly narrowed, the incision surface is more even and the deformation can be reduced. 2. If the cutting speed is too fast, the energy of the cutting line is lower than the required amount. The jet in the slit cannot quickly blow off the melted cutting melt to form a large rear drag, accompanied with slag, incision Surface quality declines. 3. When the cutting speed is too low, because the cutting point 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 conducting current place near the nearest kerf to the arc, and it will also flow toward the jet. Radiating more heat, so that the incision widens, melted material on both sides of the incision gathered and solidified at the bottom edge, forming a slag difficult to clean, and the upper edge of the incision due to excessive melting and heating to form a rounded corner. 4. When the speed is extremely low, the arc will even extinguish due to the wide cut. Thus, good cutting quality and cutting speed are inseparable.
Third, the arc voltage: It is generally believed that the normal output voltage of the power supply is the cutting voltage. Plasma arc cutting machines usually have higher no-load voltages and operating voltages. 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 the voltage means that the arc ç„“ value increases and the cutting ability increases. If the diameter of the jet is decreased and the flow rate of the gas is increased while the enthalpy is increased, a faster cutting speed and a better cutting quality can be obtained.
Fourth, the working gas and flow: The working gas, including cutting gas and auxiliary gas, some equipment also requires starting gas, usually according to the type of cutting material, thickness and cutting method to select the appropriate working gas. The cutting gas must not only ensure the formation of plasma jets, but also ensure that the molten metal and oxides in the cuts are removed. Excessive gas flow will take away more arc heat, making the length of the jet shorter, resulting in reduced cutting power and arc instability; too small gas flow will make the plasma arc lose its proper straightness and make the cutting Shallow depth, but also easy to produce slag; so the gas flow must be a good match with the cutting current and speed. Today's plasma arc cutting machines mostly rely on gas pressure to control the flow, because when the gun body has a constant aperture, controlling the gas pressure also controls the flow. The gas pressure used for cutting a certain plate thickness material is usually selected according to the data provided by the equipment manufacturer. If there are other special applications, the gas pressure needs to be determined by actual cutting test. The most commonly used working gases are: Argon, Nitrogen, Oxygen, Air, and H35, Argon-Nitrogen mixed gases.
1. Argon gas hardly reacts with any metal at high temperatures, and the argon plasma arc is very stable. Moreover, the nozzles and electrodes used have a long service life. However, the argon plasma arc voltage is low, the enthalpy value is not high, the cutting ability is limited, and the cut thickness is reduced by about 25% compared with air cutting. In addition, in an argon-protected environment, the surface tension of the molten metal is large, which is about 30% higher than that in a nitrogen atmosphere, so there are many problems with slagging. Even when using a mixture of argon and other gases, there is a tendency for sticky slag. Therefore, pure argon is rarely used alone for plasma cutting.
2. Hydrogen is usually used as an auxiliary gas to mix with other gases. For example, the famous gas, H35 (volume fraction of hydrogen is 35%, and the rest is argon) is one of the gases with the strongest plasma arc cutting ability. This is mainly due to hydrogen. . Since hydrogen can significantly increase the arc voltage, the hydrogen plasma jet has a high enthalpy. When used in combination with argon gas, the cutting ability of the plasma jet is greatly improved. Generally, argon is used as a cutting gas for metal materials having a thickness of 70 mm or more. If the water jet is used to further compress the argon + hydrogen plasma arc, higher cutting efficiency can also be achieved.
3. Nitrogen is a commonly used working gas. Under the conditions of higher power supply voltage, nitrogen plasma arc has better stability and higher jet energy than argon, even if it is a material with large liquid metal viscosity In stainless steel and nickel-base alloys, the amount of dross on the lower edge of the cut is also small. Nitrogen can be used alone or mixed with other gases. For example, nitrogen or air is often used as a working gas in automated cutting. These two gases have become standard gases for high-speed cutting of carbon steel. Nitrogen is also sometimes used as starting gas for oxygen plasma arc cutting.
4, oxygen can increase the speed of cutting low-carbon steel materials. When using oxygen for cutting, the cutting mode and flame cutting are imaginable. The high temperature and high energy plasma arc makes the cutting speed faster, but it must be used in conjunction with an electrode that resists high temperature oxidation, and at the same time, the electrode is protected against impact when starting arc to extend the electrode. Life expectancy.
5, the air contains about 78% of the nitrogen content of the volume, so the use of air cutting slag formation and cutting with nitrogen is very imaginable; the air also contains about 21% volume of oxygen, because of the presence of oxygen, with air The speed of cutting low-carbon steel materials is also high; at the same time, air is the most economical working gas. However, when using air cutting alone, there are problems such as slag dregs, incision oxidation, nitrogen addition, etc., and the low life of electrodes and nozzles will also affect work efficiency and cutting cost.
V. Nozzle height: It refers to the distance between the end surface of the nozzle and the cutting surface, which forms part of the entire arc length. Since plasma arc cutting generally uses a power source with constant current or steep drop characteristics, after the height of the nozzle is increased, the current change is small, but the arc length is increased and the arc voltage is increased, thereby increasing the arc power; but at the same time, The arc length exposed to the environment increases, and the energy lost from the arc column increases. In the case of a combination of two factors, the role of the former is often completely offset by the latter, but will reduce the effective cutting energy, resulting in reduced cutting ability. It is usually manifested that the blowing force of the cutting jet is weakened, the residual slag at the lower part of the incision is increased, and the upper edge is over-melted and rounded. In addition, considering the form of the plasma jet, the diameter of the jet expands outward after leaving the muzzle, and the increase in the height of the nozzle inevitably causes the width of the slit to increase. Therefore, choosing the smallest possible nozzle height is beneficial for increasing the cutting speed and cutting quality. However, if the nozzle height is too low, double arcing may occur. The nozzle height can be set to zero by using a ceramic outer nozzle, that is, the end face of the nozzle directly contacts the surface to be cut, and a good effect can be obtained.
6. Cutting Power Density: In order to obtain high compressibility plasma arc cutting arc, the cutting nozzle adopts a smaller nozzle hole diameter, a longer hole length and an enhanced cooling effect, so that the current passing through the effective section of the nozzle can be increased. That is, the power density of the arc increases. However, at the same time, the compression also increases the power loss of the arc. Therefore, the effective energy actually used for cutting is smaller than the output power of the power supply. The loss rate is generally between 25% and 50%. Some methods such as water compression plasma arc cutting The energy loss rate will be even greater, and this should be taken into account when performing economic calculations for cutting process parameters or cutting costs.
For example , the thickness of metal plates used in industry is mostly below 50mm. In this thickness range, conventional plasma arc cutting will often result in the formation of large and small cuts, and the upper edge of the cut will also result in the dimensional accuracy of the cuts. Decrease and increase the amount of follow-up processing. When using oxygen and nitrogen plasma arc cutting of carbon steel, aluminum and stainless steel, when the plate thickness is in the range of 10~25mm, the thicker the material is usually, the better the perpendicularity of the end edge is, and the angular error of the cutting edge is 1 Degree ~ 4 degrees. When the plate thickness is less than 1mm, the incision angle error increases from 3 degrees to 4 degrees to 15 degrees to 25 degrees as the plate thickness decreases.
It is generally believed that the cause of this phenomenon is due to the unbalanced heat input of the plasma jet on the cut surface, that is, more plasma arc energy is released in the upper part of the cut than in the lower part. This imbalance in energy release is closely related to many process parameters such as plasma arc compression, cutting speed, and nozzle-to-workpiece distance. Increasing the compression of the arc can extend the high-temperature plasma jet, creating a more uniform high-temperature region, and at the same time increase the jet velocity, which can reduce the width difference between the upper and lower incisions. However, the over-compression of conventional nozzles tends to cause double-arc phenomenon. The double-arc not only loses the electrodes and nozzles, so that the cutting process can not be performed, and the quality of the incisions also decreases. In addition, excessive cutting speeds and excessive nozzle heights can cause an increase in the difference between the upper and lower width of the cut.
The high-performance Rapier and Trident CNC plasma cutting systems focus on the previous scientific achievements of HG-FARLEYLASERLAB. The new gas control box design provides users with excellent cutting quality and quality stability, maximized production efficiency, and minimal operation. Cost, unmatched processing applicability, and better cutting quality than ever before at half the operating cost. Fine-featured parts with excellent quality and stability when cutting carbon steel. In combination with a high-precision cutting table, excellent small parts and round hole quality can be obtained. In the cutting of stainless steel and aluminum, the use of N2/N2, H35 (argon hydrogen premixed gas) and H35–N2 processes, as well as the new F5 (Nitrogen Hydrogen Premixed Gas) process, to make the quality of the cutting of the sheet significantly improved.
First, the cutting current: It is the most important cutting process parameters, directly determines the cutting thickness and speed, the cutting ability. Influencing: 1. Increased cutting current, increased arc energy, increased cutting capacity, increased cutting speed, 2. Increased cutting current, increased arc diameter, thicker arc, wider incision, 3. Cutting current As a result, the thermal load of the nozzle increases, the nozzle is damaged prematurely, and the cutting quality naturally decreases, and even normal cutting cannot be performed. Therefore, the cutting current and the corresponding nozzle should be selected correctly according to the thickness of the material before cutting.
Second, the cutting speed: The best cutting speed range can be selected according to equipment instructions or determined by tests, due to the thickness of the material, different materials, high and low melting point, thermal conductivity and surface tension after melting and other factors, cutting speed Corresponding changes. The main performances are as follows: 1. Moderately improved cutting speed can improve the quality of the incision, that is, the incision is slightly narrowed, the incision surface is more even and the deformation can be reduced. 2. If the cutting speed is too fast, the energy of the cutting line is lower than the required amount. The jet in the slit cannot quickly blow off the melted cutting melt to form a large rear drag, accompanied with slag, incision Surface quality declines. 3. When the cutting speed is too low, because the cutting point 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 conducting current place near the nearest kerf to the arc, and it will also flow toward the jet. Radiating more heat, so that the incision widens, melted material on both sides of the incision gathered and solidified at the bottom edge, forming a slag difficult to clean, and the upper edge of the incision due to excessive melting and heating to form a rounded corner. 4. When the speed is extremely low, the arc will even extinguish due to the wide cut. Thus, good cutting quality and cutting speed are inseparable.
Third, the arc voltage: It is generally believed that the normal output voltage of the power supply is the cutting voltage. Plasma arc cutting machines usually have higher no-load voltages and operating voltages. 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 the voltage means that the arc ç„“ value increases and the cutting ability increases. If the diameter of the jet is decreased and the flow rate of the gas is increased while the enthalpy is increased, a faster cutting speed and a better cutting quality can be obtained.
Fourth, the working gas and flow: The working gas, including cutting gas and auxiliary gas, some equipment also requires starting gas, usually according to the type of cutting material, thickness and cutting method to select the appropriate working gas. The cutting gas must not only ensure the formation of plasma jets, but also ensure that the molten metal and oxides in the cuts are removed. Excessive gas flow will take away more arc heat, making the length of the jet shorter, resulting in reduced cutting power and arc instability; too small gas flow will make the plasma arc lose its proper straightness and make the cutting Shallow depth, but also easy to produce slag; so the gas flow must be a good match with the cutting current and speed. Today's plasma arc cutting machines mostly rely on gas pressure to control the flow, because when the gun body has a constant aperture, controlling the gas pressure also controls the flow. The gas pressure used for cutting a certain plate thickness material is usually selected according to the data provided by the equipment manufacturer. If there are other special applications, the gas pressure needs to be determined by actual cutting test. The most commonly used working gases are: Argon, Nitrogen, Oxygen, Air, and H35, Argon-Nitrogen mixed gases.
1. Argon gas hardly reacts with any metal at high temperatures, and the argon plasma arc is very stable. Moreover, the nozzles and electrodes used have a long service life. However, the argon plasma arc voltage is low, the enthalpy value is not high, the cutting ability is limited, and the cut thickness is reduced by about 25% compared with air cutting. In addition, in an argon-protected environment, the surface tension of the molten metal is large, which is about 30% higher than that in a nitrogen atmosphere, so there are many problems with slagging. Even when using a mixture of argon and other gases, there is a tendency for sticky slag. Therefore, pure argon is rarely used alone for plasma cutting.
2. Hydrogen is usually used as an auxiliary gas to mix with other gases. For example, the famous gas, H35 (volume fraction of hydrogen is 35%, and the rest is argon) is one of the gases with the strongest plasma arc cutting ability. This is mainly due to hydrogen. . Since hydrogen can significantly increase the arc voltage, the hydrogen plasma jet has a high enthalpy. When used in combination with argon gas, the cutting ability of the plasma jet is greatly improved. Generally, argon is used as a cutting gas for metal materials having a thickness of 70 mm or more. If the water jet is used to further compress the argon + hydrogen plasma arc, higher cutting efficiency can also be achieved.
3. Nitrogen is a commonly used working gas. Under the conditions of higher power supply voltage, nitrogen plasma arc has better stability and higher jet energy than argon, even if it is a material with large liquid metal viscosity In stainless steel and nickel-base alloys, the amount of dross on the lower edge of the cut is also small. Nitrogen can be used alone or mixed with other gases. For example, nitrogen or air is often used as a working gas in automated cutting. These two gases have become standard gases for high-speed cutting of carbon steel. Nitrogen is also sometimes used as starting gas for oxygen plasma arc cutting.
4, oxygen can increase the speed of cutting low-carbon steel materials. When using oxygen for cutting, the cutting mode and flame cutting are imaginable. The high temperature and high energy plasma arc makes the cutting speed faster, but it must be used in conjunction with an electrode that resists high temperature oxidation, and at the same time, the electrode is protected against impact when starting arc to extend the electrode. Life expectancy.
5, the air contains about 78% of the nitrogen content of the volume, so the use of air cutting slag formation and cutting with nitrogen is very imaginable; the air also contains about 21% volume of oxygen, because of the presence of oxygen, with air The speed of cutting low-carbon steel materials is also high; at the same time, air is the most economical working gas. However, when using air cutting alone, there are problems such as slag dregs, incision oxidation, nitrogen addition, etc., and the low life of electrodes and nozzles will also affect work efficiency and cutting cost.
V. Nozzle height: It refers to the distance between the end surface of the nozzle and the cutting surface, which forms part of the entire arc length. Since plasma arc cutting generally uses a power source with constant current or steep drop characteristics, after the height of the nozzle is increased, the current change is small, but the arc length is increased and the arc voltage is increased, thereby increasing the arc power; but at the same time, The arc length exposed to the environment increases, and the energy lost from the arc column increases. In the case of a combination of two factors, the role of the former is often completely offset by the latter, but will reduce the effective cutting energy, resulting in reduced cutting ability. It is usually manifested that the blowing force of the cutting jet is weakened, the residual slag at the lower part of the incision is increased, and the upper edge is over-melted and rounded. In addition, considering the form of the plasma jet, the diameter of the jet expands outward after leaving the muzzle, and the increase in the height of the nozzle inevitably causes the width of the slit to increase. Therefore, choosing the smallest possible nozzle height is beneficial for increasing the cutting speed and cutting quality. However, if the nozzle height is too low, double arcing may occur. The nozzle height can be set to zero by using a ceramic outer nozzle, that is, the end face of the nozzle directly contacts the surface to be cut, and a good effect can be obtained.
6. Cutting Power Density: In order to obtain high compressibility plasma arc cutting arc, the cutting nozzle adopts a smaller nozzle hole diameter, a longer hole length and an enhanced cooling effect, so that the current passing through the effective section of the nozzle can be increased. That is, the power density of the arc increases. However, at the same time, the compression also increases the power loss of the arc. Therefore, the effective energy actually used for cutting is smaller than the output power of the power supply. The loss rate is generally between 25% and 50%. Some methods such as water compression plasma arc cutting The energy loss rate will be even greater, and this should be taken into account when performing economic calculations for cutting process parameters or cutting costs.
For example , the thickness of metal plates used in industry is mostly below 50mm. In this thickness range, conventional plasma arc cutting will often result in the formation of large and small cuts, and the upper edge of the cut will also result in the dimensional accuracy of the cuts. Decrease and increase the amount of follow-up processing. When using oxygen and nitrogen plasma arc cutting of carbon steel, aluminum and stainless steel, when the plate thickness is in the range of 10~25mm, the thicker the material is usually, the better the perpendicularity of the end edge is, and the angular error of the cutting edge is 1 Degree ~ 4 degrees. When the plate thickness is less than 1mm, the incision angle error increases from 3 degrees to 4 degrees to 15 degrees to 25 degrees as the plate thickness decreases.
It is generally believed that the cause of this phenomenon is due to the unbalanced heat input of the plasma jet on the cut surface, that is, more plasma arc energy is released in the upper part of the cut than in the lower part. This imbalance in energy release is closely related to many process parameters such as plasma arc compression, cutting speed, and nozzle-to-workpiece distance. Increasing the compression of the arc can extend the high-temperature plasma jet, creating a more uniform high-temperature region, and at the same time increase the jet velocity, which can reduce the width difference between the upper and lower incisions. However, the over-compression of conventional nozzles tends to cause double-arc phenomenon. The double-arc not only loses the electrodes and nozzles, so that the cutting process can not be performed, and the quality of the incisions also decreases. In addition, excessive cutting speeds and excessive nozzle heights can cause an increase in the difference between the upper and lower width of the cut.
The high-performance Rapier and Trident CNC plasma cutting systems focus on the previous scientific achievements of HG-FARLEYLASERLAB. The new gas control box design provides users with excellent cutting quality and quality stability, maximized production efficiency, and minimal operation. Cost, unmatched processing applicability, and better cutting quality than ever before at half the operating cost. Fine-featured parts with excellent quality and stability when cutting carbon steel. In combination with a high-precision cutting table, excellent small parts and round hole quality can be obtained. In the cutting of stainless steel and aluminum, the use of N2/N2, H35 (argon hydrogen premixed gas) and H35–N2 processes, as well as the new F5 (Nitrogen Hydrogen Premixed Gas) process, to make the quality of the cutting of the sheet significantly improved.
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