High-speed cutting technology: the transformative power of CNC custom machining

In 1931, Dr. Carl Salom of Germany first proposed the theory of high-speed jet machining, and since then, high-speed cutting technology has experienced a long history of development. From the theoretical research and exploration stage, to the applied basic research exploration stage, and then to the applied research stage, it has now entered the development and application stage.

In the process of development, key technologies are constantly being developed. For example, high-speed spindle technology, since the emergence of high-speed cutting machine tools in the 11th Japan International Machine Tool Show in 1982, the number of high-speed machine tools has increased significantly year by year. The spindle speed has been developed from more than 10000r/min at the beginning to 100000r/min or even higher today. The key technologies of high speed spindle include ceramic bearing structure and oil mist lubrication. At present, machine tool spindle systems with dn values above 1.5×10⁶ are almost all ceramic bearings.

The progress of high speed and high acceleration of the feed system is also outstanding. The application of large lead screw and the emergence of direct drive mode of linear motor meet the needs of feed system performance of zero drive machine tools, with high positioning accuracy, repeated positioning accuracy and dynamic response speed.

High-speed cutting technology has different development characteristics in different stages of CNC custom machining. In the early stage, it was mainly theoretical exploration, and with the progress of technology, it gradually showed advantages in practical application. Today, high-speed cutting technology has been widely used in aerospace, automotive, mold processing and other industries, and it is also playing an increasingly important role in the field of CNC custom machining.

The high-speed spindle has made continuous breakthroughs in technology, using advanced technologies such as ceramic bearings and hydrostatic bearings. Ceramic bearing has the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, which can effectively improve the life and load capacity of high-speed spindle. At present, the machine tool spindle system with dn value above 1.5×10⁶ almost all adopt ceramic bearings. In addition, the development of aerostatic spindle and maglev bearing support spindle has also brought new breakthroughs to high-speed spindle. For example, the ASV-40 machining center manufactured by Toshiba Machinery Company of Japan uses an aerostatic spindle with a spindle speed of 80000r/min; The high speed machining center manufactured by Mori Seiki, Japan, uses a high speed spindle supported by maglev bearings, and its speed can reach 40000r/min. These advanced spindle technologies greatly improve spindle speed and accuracy, providing strong support for high-speed cutting.

High-speed feed system in the structure of continuous innovation, the use of high-speed lead ball screw, linear motor and other advanced structures, greatly improve the feed speed and acceleration. The feed speed of high-speed lead ball screw is as high as 60m/min, and the more common is 20 ~ 30m/min. The application of linear motor has brought revolutionary changes to the high-speed feed system. The linear motor eliminates the clearance and elastic deformation of the mechanical transmission system, reduces the transmission friction, and has almost no reverse clearance. The linear motor has high acceleration and deceleration characteristics, and the acceleration can reach 2g, which is 10 to 20 times of the traditional drive device, and the feed speed is 4 to 5 times of the traditional one. Driven by linear motor, it has the obvious advantages of large thrust per unit area, easy to produce high-speed movement, and mechanical structure does not need maintenance. The application of these technologies meets the requirements of fast moving and accurate positioning of machine tools, and provides a reliable guarantee for high-speed cutting.

Cutting tools play a vital role in high-speed cutting. With the increase of cutting speed, the material, geometrical parameters and structure of tool body have changed greatly. At present, the commonly used high-speed cutting tool materials are polycrystalline diamond (PCD), cubic boron nitride (CBN), ceramics, Ti (C,N) base ceramics, coated tools (CVD), ultrafine grain carbide and so on. These tool materials have high heat resistance, thermal shock resistance, good high temperature mechanical properties and high reliability. At the same time, the tool system of high-speed cutting must meet the requirements of good geometric accuracy and high clamping repeated positioning accuracy, clamping stiffness, good balance state and safety and reliability during high-speed operation. Reduce the mass of the tool body as much as possible to reduce the centrifugal force suffered by high-speed rotation, meet the safety requirements of high-speed cutting, and improve the clamping mode of the tool.

The optimization of process parameters of high-speed cutting is one of the key technologies restricting the application of high-speed cutting. Because high-speed cutting is a new cutting mode, there is a lack of reference application examples and practical cutting parameters and machining parameters database. Therefore, it is necessary to study and adopt a new programming method to make the cutting data suitable for the power characteristic curve of the high-speed spindle, and give full play to the advantages of CNC high-speed cutting. The development and application of high-speed cutting technology depends on the comprehensive development of key unit technologies such as high-speed spindle, high-speed feed system and high-speed cutting tools. Only the coordination of various technologies can achieve high efficiency, high precision and high reliability of high-speed cutting.

High-speed cutting technology has many advantages in CNC high-speed milling of aluminum alloy cavity shell. First of all, it can improve the processing efficiency, CNC high-speed cutting allows the use of a larger feed rate, 5 to 10 times higher than conventional cutting, per unit time material removal rate can be increased by 3 to 6 times. It is of great significance for CNC machining of aluminum alloy cavity parts and can greatly reduce processing time. Secondly, it can ensure the processing quality, and compared with conventional cutting, the cutting force can be reduced by at least 30% during high-speed cutting, reducing the processing deformation. High-speed cutting process is fast, more than 95% of the cutting heat is very little, parts will not cause warping or expansion deformation due to temperature rise, especially suitable for processing parts that are easy to heat deformation. In terms of machining tool and feed speed selection, the cutting speed of the whole carbide end mill for processing aluminum alloy parts can generally reach 1000m/min. If the D8 end mill is used, the spindle speed is determined to be 18000r/min, the roughing feed speed is set to 6000mm/min, and the finishing feed speed can be selected to be 2000-3000mm /min considering the rigidity of the cavity shell workpiece and the surface quality requirements of the parts. If the machine tool performance is high, the cutting speed and feed speed can be appropriately increased.

In the actual production, high-speed machining technology has a wide range of applications. To a typical roughing example, the first use of 5-inch TiAIN coating insert edge face milling cutter, spindle speed 450 ~ 500 rpm, feed rate 150 ~ 175 ipm, cutting depth 0.050 inches, processing a large number of chips flying. After roughing, most of the workpiece is sent outside for heat treatment. Semi-finishing begins as soon as the workpiece is returned, usually with a 2-inch ball-end mill at 2000 rpm and a feed speed of 125 to 150 ipm. For profile cutting following a reciprocating milling pattern, the track spacing is within 0.125 inches. For zigzag cutting, similar speeds and feed speeds, 0.020 to 0.050 "depth of cut, and a small 2.5" diameter head can be used. In addition, smaller tools can also be used to connect the chamfer.

High-speed cutting has special requirements for CNC systems. Because the spindle speed and cutter feed speed of high-speed cutting machine tools are greatly increased, the CNC system is required to have enough fast computing speed and data processing ability. The feed servo mechanism should be able to realize arbitrary adjustment in a wide range from low speed to high speed, and overcome the contradiction of large system following error when the feed servo speed is high. The CNC system is required to have a shorter servo cycle and higher resolution, while having the monitoring function of the trajectory to be machine. curve interpolation capability.

At present, there are some problems in CNC system of high-speed cutting. First, the architecture is closed, which limits the scalability and compatibility of the system. Secondly, there is insufficient integration with CAM, resulting in less smooth and efficient programming and processing. Furthermore, the interpolators and feed controllers of CNC systems have limitations. The interpolation precision needs to be improved, and the function of feedforward and large number of advanced program segments should be used. In addition, the contour control technology such as NURBS interpolation, recoil acceleration, smooth interpolation, bell acceleration and deceleration can also be used. The feed controller needs to better cope with the high acceleration and fast response requirements of high-speed cutting.

Stainless steel parts are faced with the trend of work hardening in the process of high-speed cutting, which brings many problems to the processing. Different kinds of stainless steel due to different mechanical properties and chemical composition, the difficulty of CNC cutting is not the same. High thermal strength and toughness are not easy to be cut off during CNC high-speed cutting, and the work consumed during cutting deformation is quite large. The depth of the work hardening layer can range from tens of microns to hundreds of microns, and the work hardening phenomenon generated by the previous cutting has an adverse effect on the next cutting, and the high hardness of the work hardening layer causes the tool to be particularly easy to wear.

In order to solve the problem of work hardening, you can choose the right tool, such as a cutting edge shape with an emphasis on sharpness, good sharpness can reduce the heat generated by friction with the workpiece, thereby preventing work hardening. At the same time, it is necessary to set the best processing conditions and the best coolant Settings.

The application of high-speed cutting technology also faces challenges such as strong chip adhesion and poor thermal conductivity. In the CNC cutting process, cutting debris is easy to adhere to or melt on the tip of the tool and the blade, forming a chip tumor, causing the surface roughness of the workpiece processing surface to deteriorate, while increasing the vibration during the cutting process and accelerating tool wear. And a large amount of cutting heat can not be conducted out in time, and even the heat generated by cutting can not be conducted to the whole chip, resulting in the total heat of the incoming tool than ordinary carbon steel, so that the cutting edge loses the cutting performance at high temperature.

In addition, high-speed cutting, as a new cutting mode, lacks of reference application examples and practical cutting parameters and machining parameters database. This makes it necessary to constantly test and explore in practical applications, increasing the processing cost and time.

High speed cutting technology has great potential in improving production efficiency because of its high speed, high precision and high surface quality. First of all, high-speed cutting can significantly shorten the production cycle. For example, in the automotive manufacturing industry, high-speed cutting technology can quickly process key components such as engine blocks and transmission housings, greatly reducing processing time and improving production efficiency. According to the relevant statistics, after the adoption of high-speed cutting technology, the processing time of auto parts can be reduced by 30% to 50%. Secondly, high-speed cutting technology can reduce processing costs. Because high-speed cutting can achieve a rough machining, semi-finishing and finishing processes, the use of processes and tools is reduced, thus reducing production costs. Taking mold manufacturing as an example, high-speed cutting technology can reduce the use of EDM, reduce processing costs, and improve the accuracy and surface quality of the mold. In addition, high-speed cutting technology can also improve product quality. When cutting at high speed, the cutting force is small and the vibration is small, it can process very precise parts, and the surface roughness is reduced by 1 to 2 levels, which meets the needs of modern manufacturing industry for high-precision products.

The development of high-speed cutting technology will promote the development of machinery manufacturing industry to the direction of high efficiency, high precision, high flexibility and green. On the one hand, the application of high-speed cutting technology will promote the technological progress of the machinery manufacturing industry. High-speed cutting technology requires the support of a number of advanced technologies such as high-speed cutting machine tools, high-speed cutting tools, high-performance numerical control systems, and the development of these technologies will drive the technical level of the entire machinery manufacturing industry. For example, the research and development of high-speed cutting machine tools requires advanced spindle technology, feed system technology and structural design technology, and breakthroughs in these technologies will provide more advanced processing equipment for the machinery manufacturing industry. On the other hand, the promotion of high-speed cutting technology will improve the competitiveness of the machinery manufacturing industry. Under the background of increasingly fierce competition in the global manufacturing industry, high-speed cutting technology can improve product quality, reduce production costs, shorten production cycle, and win market competitive advantages for enterprises. Taking the aerospace manufacturing industry as an example, high-speed cutting technology can process lightweight materials such as aluminum alloy and titanium alloy, improve the performance and safety of aircraft, and enhance the competitiveness of enterprises in the international market.

In the future, the key technology research of high-speed cutting technology will develop in the direction of higher speed, higher precision and more intelligent. In terms of high-speed cutting machine tools, the spindle speed and feed speed will be further improved, and more advanced spindle systems and feed systems will be developed to improve the rigidity and stability of the machine tool. For example, the spindle system using magnetic levitation technology and aerostatic pressure technology can reach more than 100,000 RPM; The feed system using linear motor and grating scale feedback technology can accelerate up to 5g and the positioning accuracy can reach micron level. In terms of high-speed cutting tools, more advanced tool materials and coating technologies will be developed to improve the hardness, wear resistance and heat resistance of tools. For example, the hardness of the tool using nano coating technology can be increased by 2 to 3 times, and the wear resistance can be increased by 5 to 10 times. In terms of numerical control systems, more advanced programming technology and control algorithms will be developed to improve the computing speed and data processing capacity of numerical control systems. For example, numerical control systems using artificial intelligence technology and big data analysis technology can automatically optimize cutting parameters according to the characteristics of machining materials and tools, improving processing efficiency and quality.

At the application level, high-speed cutting technology will continue to expand the application field and achieve a wider range of applications. On the one hand, high-speed cutting technology will be more widely used in the traditional manufacturing industry. For example, in the fields of machinery manufacturing, automobile manufacturing, aerospace manufacturing, high-speed cutting technology will gradually replace traditional cutting technology and become the mainstream processing method. On the other hand, high-speed cutting technology will be applied in the emerging manufacturing sector. For example, in the fields of 3D printing, micro and nano manufacturing, biomedical manufacturing and so on, high-speed cutting technology can be combined with other advanced manufacturing technologies to achieve high-precision machining of complex shaped parts. In addition, high-speed cutting technology will develop in the direction of green manufacturing. For example, the use of dry cutting technology and micro-lubrication technology can reduce the use of cutting fluid, reduce environmental pollution, and achieve green manufacturing.