The high-speed machining (HSC) that emerged in the late 1980s greatly shortened the machining time and improved the surface quality and machining accuracy due to the significant increase in cutting speed and feed rate. Therefore, the reduction of processing procedures and the simplification of the production process, as well as the transformation of production methods in some industries, have effectively promoted the development of the entire production technology.
High-speed machining combines the two contradictory characteristic parameters of “productivity†and “flexibility†to replace the traditional rigid automatic line with a flexible production system composed of high-speed machining centers, which promotes production modes in medium and large-scale production industries such as automobiles. The transformation.
High-speed machining leads to process replacement, which simplifies the production process. A typical example of high-speed hard milling instead of EDM in mold manufacturing is that the hardened workpiece can be finished into a finished product by rough milling and high-speed finishing milling in one setup. The application of high-speed hard milling has created conditions for the integration of CAD-CAM-HSC in mold manufacturing. The high-speed hard milling process has undoubtedly brought about a major change in mold manufacturing technology.
For more than a decade since the beginning of high-speed machining, high-speed machining technology has been widely promoted and applied. In production, through high-speed machining, the basic time is significantly shortened, and the ratio of auxiliary time to basic time is increased accordingly (from the past 7%: 93% to the current 35%: 65% for aluminum alloy workpieces) Processing, this ratio has reached 50%: 50%). From the current state of the art, the potential to further reduce the basic time through high-speed machining is not great.
In recent years, in order to further improve production efficiency, more and more efficient processing (HPC) is used to increase the amount of material removed per unit time and significantly reduce the auxiliary time to further reduce the basic time and auxiliary time during the cutting process.
High-efficiency machining (HPC) differs from high-speed machining (HSC) in that
It is not limited to increasing the cutting speed and feed rate, but puts the optimized material removal rate in the first place, aiming to further reduce the processing cost by increasing the amount of material removed per unit time and reducing the processing time (basic time and auxiliary time). .
The material removal rate (Q) is determined by the amount of side knife (ae), the amount of back knife (ap), and the feed rate (vf). For milling, the feed rate (vf) is again dependent on the feed per tooth (fz), the number of teeth (z) and the speed of the milling cutter (n).
The amount of material removal per unit time can be expressed by Q = ae · ap · vf / 1000 = ae · ap · fz · z · n / 1000 (cm3 / min).
We can see from this expression that the material removal rate is related to five cutting parameters, so efficient machining can, but does not have to, include high-speed machining, which means that there is no clear boundary between efficient machining and high-speed machining.
The aviation industry is the first department to apply high-speed machining and high-efficiency machining. The bearing members such as beams, frames and large siding of the aircraft are made of integral structural parts. When processing, 75%~95% of the blanks will be cut off. For this particularly high cutting amount, it is undoubtedly efficient to process. The most suitable. The EADS (European Aerospace Defense and Space Company) in Augsburg, Germany, used the HSC process to process an aluminum alloy monolithic component of a military aircraft in the 1990s. The main purpose was to simplify the production process with less The process achieved high surface quality, rather than increasing the material removal rate. 54 tools were used in the process and it took a total of 25 hours to complete the process. In order to further tap the potential of productivity, it was natural to turn to efficient machining, using 40 tools, processing time was only 12 hours, a reduction of more than half.
Especially for milling, the material removal rate that can be achieved by milling cutters has become an important indicator to measure the economics of milling cutters. In recent years, many tool manufacturers have developed a number of milling cutters with high feed rates. Although these milling cutters are not identical in construction, a common feature is the geometry of the blade that is suitable for high speed feed. This geometry is characterized by a large arc radius of the cutting edge, which slightly limits the amount of backing (ap) of the milling cutter, and the diameter acting on the milling cutter due to the smaller main declination The cutting force is greatly reduced, which facilitates machining with a high feed per tooth.
For example, when roughing 40CrMnMoS86 glass bottles, the Franken tool factory in Germany compares the milling results with a milling cutter with three round inserts and a high feed speed cutter with three Time-S-Cut inserts. The cutting amount used by the former is Vc=250m/min, fz=0.3mm, ap=0.75mm and ae=18mm, and it is cooled by cold compressed air during processing, and the processing time is 9 minutes. In the latter, the latter reduced the ap to 0.5 mm and the fz to 1.0 mm, resulting in a processing time of only 4 minutes. In terms of time savings, it reached 55%, which means that the machine tool saved 55% per hour.
It can be seen from this that by using higher cutting parameters, high-efficiency machining can achieve high material removal rates and significantly reduce machining time. However, efficient machining is not just about using very high cutting parameters, but also efficient machining through other machining strategies that significantly reduce auxiliary time. For example, the use of composite tools (such as composite step drills, drilling and milling thread tools and other composite tools for integrated machining), multi-purpose end mills such as circumferential feed milling, and other advanced tools can significantly reduce the number of tool changes and reduce the auxiliary time. , thereby significantly improving production efficiency.
The composite tool integrates multiple machining processes on one tool, and often realizes comprehensive machining of multiple machining parts in one machining stroke. This tool not only eliminates the need for tool change but also improves machining accuracy and can be omitted. Accuracy measurement between processes can significantly increase production efficiency.
When milling a hole in a machining center with a multi-function end mill, the number of tool changes can also be reduced. When milling the hole, the rotating milling cutter makes a helical interpolation motion around the Z axis, and the hole of the required size can be processed in one working stroke. For example, machining a hole with a diameter of 285 mm and using a 160 mm diameter milling cutter can complete the machining task in one working stroke, which can achieve five reaming operations and save 73% of machining time compared to conventional processes.
In recent years, the advent of high-efficiency deep-hole drills has significantly improved the efficiency of deep-hole drilling. A double-edged solid carbide twist drill developed by Gühring, Germany, has a drilling aperture ratio (l/D) of 20. In the case of deep holes, the use of micro-lubrication (6~8ml/h) not only adopts a feed speed 10~12 times higher than the traditional high-flow wet drilling, but also does not require chip evacuation during the drilling process. Improve processing efficiency. Moreover, the radial offset of the drill bit during drilling is particularly small, and a good surface quality can be obtained.
In production, high-speed machining and high-efficiency machining processes have been widely promoted and applied. The common feature of these two processes is that they can significantly reduce the processing time and shorten the production process. The different characteristics are that high-speed machining uses high cutting speed. The aim is to achieve high surface quality and streamline the process, so high-speed machining is more suitable for finishing; while high-efficiency machining mainly uses high cutting parameters to obtain high material removal per unit time, thus significantly reducing processing. time. Efficient machining for high material removal rates is suitable for roughing. In actual production, these two machining processes can be applied simultaneously to machine a workpiece. For example, high-precision machining can be used for rough milling (to achieve high material removal rate) while machining, while high-speed machining is used in finishing. For better surface quality and high processing accuracy).
At present, both high-speed machining and high-efficiency machining, which are popular, should be based on the continuous development of tool technology, especially in the continuous development and optimization of tool materials, blade geometry and coatings. A highly efficient tool with different structures provides the basis. Production practices have shown that in order to significantly reduce processing time, increase production efficiency and reduce part manufacturing costs, the key is to use high-speed machining and efficient processing.
High-speed machining combines the two contradictory characteristic parameters of “productivity†and “flexibility†to replace the traditional rigid automatic line with a flexible production system composed of high-speed machining centers, which promotes production modes in medium and large-scale production industries such as automobiles. The transformation.
High-speed machining leads to process replacement, which simplifies the production process. A typical example of high-speed hard milling instead of EDM in mold manufacturing is that the hardened workpiece can be finished into a finished product by rough milling and high-speed finishing milling in one setup. The application of high-speed hard milling has created conditions for the integration of CAD-CAM-HSC in mold manufacturing. The high-speed hard milling process has undoubtedly brought about a major change in mold manufacturing technology.
For more than a decade since the beginning of high-speed machining, high-speed machining technology has been widely promoted and applied. In production, through high-speed machining, the basic time is significantly shortened, and the ratio of auxiliary time to basic time is increased accordingly (from the past 7%: 93% to the current 35%: 65% for aluminum alloy workpieces) Processing, this ratio has reached 50%: 50%). From the current state of the art, the potential to further reduce the basic time through high-speed machining is not great.
In recent years, in order to further improve production efficiency, more and more efficient processing (HPC) is used to increase the amount of material removed per unit time and significantly reduce the auxiliary time to further reduce the basic time and auxiliary time during the cutting process.
High-efficiency machining (HPC) differs from high-speed machining (HSC) in that
It is not limited to increasing the cutting speed and feed rate, but puts the optimized material removal rate in the first place, aiming to further reduce the processing cost by increasing the amount of material removed per unit time and reducing the processing time (basic time and auxiliary time). .
The material removal rate (Q) is determined by the amount of side knife (ae), the amount of back knife (ap), and the feed rate (vf). For milling, the feed rate (vf) is again dependent on the feed per tooth (fz), the number of teeth (z) and the speed of the milling cutter (n).
The amount of material removal per unit time can be expressed by Q = ae · ap · vf / 1000 = ae · ap · fz · z · n / 1000 (cm3 / min).
We can see from this expression that the material removal rate is related to five cutting parameters, so efficient machining can, but does not have to, include high-speed machining, which means that there is no clear boundary between efficient machining and high-speed machining.
The aviation industry is the first department to apply high-speed machining and high-efficiency machining. The bearing members such as beams, frames and large siding of the aircraft are made of integral structural parts. When processing, 75%~95% of the blanks will be cut off. For this particularly high cutting amount, it is undoubtedly efficient to process. The most suitable. The EADS (European Aerospace Defense and Space Company) in Augsburg, Germany, used the HSC process to process an aluminum alloy monolithic component of a military aircraft in the 1990s. The main purpose was to simplify the production process with less The process achieved high surface quality, rather than increasing the material removal rate. 54 tools were used in the process and it took a total of 25 hours to complete the process. In order to further tap the potential of productivity, it was natural to turn to efficient machining, using 40 tools, processing time was only 12 hours, a reduction of more than half.
Especially for milling, the material removal rate that can be achieved by milling cutters has become an important indicator to measure the economics of milling cutters. In recent years, many tool manufacturers have developed a number of milling cutters with high feed rates. Although these milling cutters are not identical in construction, a common feature is the geometry of the blade that is suitable for high speed feed. This geometry is characterized by a large arc radius of the cutting edge, which slightly limits the amount of backing (ap) of the milling cutter, and the diameter acting on the milling cutter due to the smaller main declination The cutting force is greatly reduced, which facilitates machining with a high feed per tooth.
For example, when roughing 40CrMnMoS86 glass bottles, the Franken tool factory in Germany compares the milling results with a milling cutter with three round inserts and a high feed speed cutter with three Time-S-Cut inserts. The cutting amount used by the former is Vc=250m/min, fz=0.3mm, ap=0.75mm and ae=18mm, and it is cooled by cold compressed air during processing, and the processing time is 9 minutes. In the latter, the latter reduced the ap to 0.5 mm and the fz to 1.0 mm, resulting in a processing time of only 4 minutes. In terms of time savings, it reached 55%, which means that the machine tool saved 55% per hour.
It can be seen from this that by using higher cutting parameters, high-efficiency machining can achieve high material removal rates and significantly reduce machining time. However, efficient machining is not just about using very high cutting parameters, but also efficient machining through other machining strategies that significantly reduce auxiliary time. For example, the use of composite tools (such as composite step drills, drilling and milling thread tools and other composite tools for integrated machining), multi-purpose end mills such as circumferential feed milling, and other advanced tools can significantly reduce the number of tool changes and reduce the auxiliary time. , thereby significantly improving production efficiency.
The composite tool integrates multiple machining processes on one tool, and often realizes comprehensive machining of multiple machining parts in one machining stroke. This tool not only eliminates the need for tool change but also improves machining accuracy and can be omitted. Accuracy measurement between processes can significantly increase production efficiency.
When milling a hole in a machining center with a multi-function end mill, the number of tool changes can also be reduced. When milling the hole, the rotating milling cutter makes a helical interpolation motion around the Z axis, and the hole of the required size can be processed in one working stroke. For example, machining a hole with a diameter of 285 mm and using a 160 mm diameter milling cutter can complete the machining task in one working stroke, which can achieve five reaming operations and save 73% of machining time compared to conventional processes.
In recent years, the advent of high-efficiency deep-hole drills has significantly improved the efficiency of deep-hole drilling. A double-edged solid carbide twist drill developed by Gühring, Germany, has a drilling aperture ratio (l/D) of 20. In the case of deep holes, the use of micro-lubrication (6~8ml/h) not only adopts a feed speed 10~12 times higher than the traditional high-flow wet drilling, but also does not require chip evacuation during the drilling process. Improve processing efficiency. Moreover, the radial offset of the drill bit during drilling is particularly small, and a good surface quality can be obtained.
In production, high-speed machining and high-efficiency machining processes have been widely promoted and applied. The common feature of these two processes is that they can significantly reduce the processing time and shorten the production process. The different characteristics are that high-speed machining uses high cutting speed. The aim is to achieve high surface quality and streamline the process, so high-speed machining is more suitable for finishing; while high-efficiency machining mainly uses high cutting parameters to obtain high material removal per unit time, thus significantly reducing processing. time. Efficient machining for high material removal rates is suitable for roughing. In actual production, these two machining processes can be applied simultaneously to machine a workpiece. For example, high-precision machining can be used for rough milling (to achieve high material removal rate) while machining, while high-speed machining is used in finishing. For better surface quality and high processing accuracy).
At present, both high-speed machining and high-efficiency machining, which are popular, should be based on the continuous development of tool technology, especially in the continuous development and optimization of tool materials, blade geometry and coatings. A highly efficient tool with different structures provides the basis. Production practices have shown that in order to significantly reduce processing time, increase production efficiency and reduce part manufacturing costs, the key is to use high-speed machining and efficient processing.
Oil Casing Pipe,Cold Drawn Steel Pipe,Carbon Steel Pipe,Seamless Steel Pipe
Tianyi Steel Pipe Co., Ltd. , http://www.czseamlesspipe.com