With the continuous development of the manufacturing industry, the world's machine tool manufacturers have been seeking new technologies to reduce the production cost of machined parts and finished products, making super-hard cutting a new processing technology of current concern to manufacturers. It is expected that in the near future, superhard cutting technology will develop more maturely and be widely used.
Ultra-hard turning technology Ultra-hard turning is defined as the process of single-point cutting of HRC 45 or higher hard materials. Generally, the hardness of the workpiece material can reach the range of HRC 58-68, and the material of the cutting tool is basically CBN (cubic boron nitride).
Ultra-hard turning technology offers a new option for machining that does not require ultra-high precision grinding. Of course, the grinding process is a suitable choice for some ultra-high precision workpieces, easily deformed workpieces and specially required workpieces. Although ultra-hard turning can not completely replace ultra-high precision grinding, it has been able to replace a considerable part of precision grinding, which reduces the expensive production cost in the grinding manufacturing process. At present, the surface roughness of workpieces with superhard cutting is generally Ra0.2～Ra0.4, the roundness can reach 0.0005mm, and the dimensional accuracy can be controlled within 0.003mm. After cutting, it is found that the ultra-hard turning process is 4 to 6 times more efficient than the general grinding process.
Cutting a hard part of the HRC 62 without cooling with a cutting fluid produces a lot of heat. In general ultra-hard cutting, the temperature in the area of ​​the cutting point can be as high as 926 °C. In fact, local high-temperature heating can help the completion of the cutting process. The high heat of the cutting point of the tool pre-anneals and softens the cutting layer of the workpiece, making the workpiece easier to cut. During this cutting process, most of the heat is generated by the peeling of the chips. In order to obtain a beautiful surface finish quality, the cutting depth should be reduced as much as possible during the last cut, generally within 0.25 mm.
Current ultra-hard turning has been widely used in the manufacture of automotive parts. Shanghai Automotive Gear Factory has successfully applied this technology to mass production. After the carburizing and quenching of the gears, they use the car to grind the final precision machining of the finished product to achieve the tolerance and surface roughness of the part design. Claim. The surface roughness of the workpiece to be machined can reach Ra0.2～Ra0.4, the roundness can reach 0.0005 mm, and the tolerance band of 0.003 mm can reach 1.67.
Stability of continuous machining An important sign of turning hard materials is to ensure the stability of continuous machining. This is related to the overall dynamic rigidity of the machine tool, the cutting tool, and the heat treatment state of the workpiece.
The use of polymer (artificial marble) to fill the main parts of the bed to increase its damping coefficient (usually 8 times that of cast iron bed), combined with the use of linear rolling guides, will have a huge impact on the turning process of superhard materials. Influence, and greatly reduce the vibration caused by cutting, increase the time to quickly return to static stiffness (see Figure 2 Figure 3). The test results show that the improvement of the machine tool effectively suppresses the chipping of the tool caused by the vibration of the machine tool, prolongs the service life of the tool, greatly improves the precision of the workpiece to be machined, reduces the dispersion of the tolerance zone, and improves the workpiece. Surface Quality.
Another important factor in machine tools is the performance and accuracy of the integration of the moving axes, including machine accuracy, geometric accuracy, electronic control functions, error compensation, and general adjustment and thermal deformation effects. This is because the final machining result of the workpiece is completely determined by the performance and accuracy of the machine.
Ceramic knives are usually used in roughing, the cutting depth is more than 0.25mm; CBN knives are used in finishing, and the cutting depth is less than 0.25mm.
In order to achieve the desired effect of turning hard materials, it is necessary to control the heat treatment state of the workpiece. Generally, the hardness change requirement of quenching is less than 2 points between HRC. If the workpiece is a carburized part, it is also necessary to control the consistency of the depth of the carburized layer. Generally, the depth should be controlled within 0.8 to 1.2 mm.
Advantages of turning hard materials Compared to grinding processes, turning of superhard materials has the following advantages:
On one lathe, both “soft cutting†and super-hard cutting can be performed. One machine is equivalent to two machine tools, which saves space in the factory and reduces the capital investment in purchasing machine tools.
The chip efficiency of ultra-hard turning is 4 to 6 times that of grinding;
In the ultra-hard turning process, the workpiece with complex shape can be processed by the single-point cutting feature of the turning tool, and the grinding machine can only be ground by the forming grinding wheel;
One set can complete multiple cutting processes, saving time for workpiece handling and re-equipment, and reducing workpiece damage;
Ultra-hard turning can easily achieve a surface roughness of Ra0.2 to Ra0.4;
The ultra-hard turning lathe can adapt to different specifications of the workpiece, especially in the mould industry, to meet the processing of different batches and complex workpieces;
The chips for ultra-hard turning are easier to handle than the grinding chips and meet environmental protection requirements;
Tool inventory costs are lower.
Ultra-hard turning is a practical technology that provides good economics and better workpiece quality, especially on high dynamic rigid machines. The ultra-hard turning process is not much different from the general turning process. Most manufacturers can introduce this new technology and apply it to actual production.
Looking forward to the future, with the continuous improvement of cutting process and machine tool performance, the new technology of ultra-hard turning will gradually become perfect and get more widely used.
Ultra-hard turning technology Ultra-hard turning is defined as the process of single-point cutting of HRC 45 or higher hard materials. Generally, the hardness of the workpiece material can reach the range of HRC 58-68, and the material of the cutting tool is basically CBN (cubic boron nitride).
Ultra-hard turning technology offers a new option for machining that does not require ultra-high precision grinding. Of course, the grinding process is a suitable choice for some ultra-high precision workpieces, easily deformed workpieces and specially required workpieces. Although ultra-hard turning can not completely replace ultra-high precision grinding, it has been able to replace a considerable part of precision grinding, which reduces the expensive production cost in the grinding manufacturing process. At present, the surface roughness of workpieces with superhard cutting is generally Ra0.2～Ra0.4, the roundness can reach 0.0005mm, and the dimensional accuracy can be controlled within 0.003mm. After cutting, it is found that the ultra-hard turning process is 4 to 6 times more efficient than the general grinding process.
Cutting a hard part of the HRC 62 without cooling with a cutting fluid produces a lot of heat. In general ultra-hard cutting, the temperature in the area of ​​the cutting point can be as high as 926 °C. In fact, local high-temperature heating can help the completion of the cutting process. The high heat of the cutting point of the tool pre-anneals and softens the cutting layer of the workpiece, making the workpiece easier to cut. During this cutting process, most of the heat is generated by the peeling of the chips. In order to obtain a beautiful surface finish quality, the cutting depth should be reduced as much as possible during the last cut, generally within 0.25 mm.
Current ultra-hard turning has been widely used in the manufacture of automotive parts. Shanghai Automotive Gear Factory has successfully applied this technology to mass production. After the carburizing and quenching of the gears, they use the car to grind the final precision machining of the finished product to achieve the tolerance and surface roughness of the part design. Claim. The surface roughness of the workpiece to be machined can reach Ra0.2～Ra0.4, the roundness can reach 0.0005 mm, and the tolerance band of 0.003 mm can reach 1.67.
Stability of continuous machining An important sign of turning hard materials is to ensure the stability of continuous machining. This is related to the overall dynamic rigidity of the machine tool, the cutting tool, and the heat treatment state of the workpiece.
The use of polymer (artificial marble) to fill the main parts of the bed to increase its damping coefficient (usually 8 times that of cast iron bed), combined with the use of linear rolling guides, will have a huge impact on the turning process of superhard materials. Influence, and greatly reduce the vibration caused by cutting, increase the time to quickly return to static stiffness (see Figure 2 Figure 3). The test results show that the improvement of the machine tool effectively suppresses the chipping of the tool caused by the vibration of the machine tool, prolongs the service life of the tool, greatly improves the precision of the workpiece to be machined, reduces the dispersion of the tolerance zone, and improves the workpiece. Surface Quality.
Another important factor in machine tools is the performance and accuracy of the integration of the moving axes, including machine accuracy, geometric accuracy, electronic control functions, error compensation, and general adjustment and thermal deformation effects. This is because the final machining result of the workpiece is completely determined by the performance and accuracy of the machine.
Ceramic knives are usually used in roughing, the cutting depth is more than 0.25mm; CBN knives are used in finishing, and the cutting depth is less than 0.25mm.
In order to achieve the desired effect of turning hard materials, it is necessary to control the heat treatment state of the workpiece. Generally, the hardness change requirement of quenching is less than 2 points between HRC. If the workpiece is a carburized part, it is also necessary to control the consistency of the depth of the carburized layer. Generally, the depth should be controlled within 0.8 to 1.2 mm.
Advantages of turning hard materials Compared to grinding processes, turning of superhard materials has the following advantages:
On one lathe, both “soft cutting†and super-hard cutting can be performed. One machine is equivalent to two machine tools, which saves space in the factory and reduces the capital investment in purchasing machine tools.
The chip efficiency of ultra-hard turning is 4 to 6 times that of grinding;
In the ultra-hard turning process, the workpiece with complex shape can be processed by the single-point cutting feature of the turning tool, and the grinding machine can only be ground by the forming grinding wheel;
One set can complete multiple cutting processes, saving time for workpiece handling and re-equipment, and reducing workpiece damage;
Ultra-hard turning can easily achieve a surface roughness of Ra0.2 to Ra0.4;
The ultra-hard turning lathe can adapt to different specifications of the workpiece, especially in the mould industry, to meet the processing of different batches and complex workpieces;
The chips for ultra-hard turning are easier to handle than the grinding chips and meet environmental protection requirements;
Tool inventory costs are lower.
Ultra-hard turning is a practical technology that provides good economics and better workpiece quality, especially on high dynamic rigid machines. The ultra-hard turning process is not much different from the general turning process. Most manufacturers can introduce this new technology and apply it to actual production.
Looking forward to the future, with the continuous improvement of cutting process and machine tool performance, the new technology of ultra-hard turning will gradually become perfect and get more widely used.
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