Current status and future development trend of CNC machining tool technology

In recent years, driven by high-tech technologies such as microelectronics, computer technology, information engineering and materials engineering, traditional manufacturing technology has developed rapidly and has rapidly developed into an emerging manufacturing technology - digital manufacturing technology. Compared with traditional manufacturing technology, its important feature is that CNC machining technology has been widely used. The driving force behind this development comes from the strong pursuit of manufacturing efficiency in manufacturing. In this context, tool manufacturing and application technology, which is mainly targeted at manufacturing, has developed rapidly. A large number of high-speed, high-efficiency, flexible, composite, environmentally-friendly CNC machining tools and new application technologies are emerging, which has caused fundamental changes in traditional cutting technology. Nowadays, hard cutting, dry cutting, high-speed and high-efficiency machining have become an important symbol of modern cutting technology, and have driven the comprehensive improvement of cutting technology, which has become a key technology for CNC machining. Tool products have evolved into high value-added, high-tech products, including the latest in the fields of contemporary materials, information science, computers, and microelectronics applications.

First, the progress of tool materials
At present, the main features of the progress of tool materials are: on the one hand, cemented carbide replaces high-speed steel as the main tool material; on the other hand, the proportion of super-hard tool materials is greatly increased.

Cemented carbide substrate
The development of new grades of cemented carbide is becoming more and more targeted. For example, Kennametal of the United States only has different turning grades for different processed materials: KC9110 for processing steel, KC9225 for processing stainless steel, KY1310 for processing cast iron, processing. KC5410 for heat-resistant alloy, KC5510 for hardened material, and KY1615 for non-ferrous materials, the new grade can increase the cutting efficiency by 15%-20% on average. The new grades of TK1000 and TK2000 for processing cast iron introduced by Seco can increase the cutting speed by 20% to 30%. The TP3000 developed by the company for processing steel is very useful in heavy cutting, interrupted cutting and large feed applications. Good reliability.

Cast iron and stainless steel are currently two types of workpiece materials, but the processability of the two is very different. Many companies have developed special grades for processing these two materials. The Black Diamond Blade series developed by Zhuzhou Diamond Cutting Tool Co., Ltd. is a carbide insert specializing in the processing of cast iron, including YBD052 for dry high speed machining of grey cast iron and YBD102 for high speed machining of ductile iron. It can be used for medium and high speed or milling. YBD152 and YBD252 grades for medium and low speed wet milling or intermittent machining. These new grades can increase cutting speed by 30% to 40% compared to the original grade, and the service life can be increased by nearly 40% to 50%. In the processing of stainless steel, Sweden Sandvik's GC2015 for turning austenitic stainless steel is a matrix with gradient zone resistance to plastic deformation and improved thermosetting, plus TiN-TiN/Al2O3 (multilayer)-TiCN designed for this grade. The coating is applied and the surface of the coating is smoothed to improve the resistance to abrasive wear, flaking and chipping resistance. KORLOY's PC9530 is a graded stainless steel grade with an ultra-fine particle substrate and PVD coating.

Emphasis on the optimal combination of substrate and coating in the development of new grades
For grades suitable for high speed machining, the substrate should have a high resistance to plastic deformation and a cobalt-rich surface and a coating resistant to crescents; for grades suitable for interrupted cutting, the substrate and coating must have good toughness. . Sandvik's special grades for turning cast iron, GC3205, GC3210 and GC3215, are CVD coated cemented carbides, which are used for high-speed machining of gray cast iron, high-speed machining of ductile iron, and medium and low-speed interrupted cutting of various cast irons. The grades are made of different cemented carbide substrates and different thicknesses of Al2O3 and MT-TiCN coatings.

UC5105 and UC5115 hard alloy CVD coating grades for turning cast iron developed by Mitsubishi Materials Corporation of Japan. The former is used for high-speed continuous cutting of gray cast iron or ductile cast iron, using a high hardness matrix, and the latter is used for the instability of ductile iron. Conditional processing, using a tough matrix; both coated with particulate Al2O3 and particulate and fibrous TiCN thick film. BOEHLERIT's cast iron grade CasttecLC620H uses a tough matrix for interrupted cutting, while Al2O3's surface coating reduces crater wear. There is also an interlocking intermediate layer to increase bond strength. 400m/min high speed machining of gray cast iron.

Superhard tool material
With the development of dry cutting and hard cutting, in recent years, foreign companies have introduced new grades of ceramic and superhard tool materials, such as Kennametal's KY4400 ceramic insert, which is a hybrid ceramic material suitable for hard turning. TiCN hard material is added to the 1?m grain size Al2O3 matrix to improve the hardness and toughness of the insert. It is suitable for hardened steel or cast iron with a hardness of 40-67 HRC. Sandvik's CT5005 nickel-free cermet blade is a new grade for ultra-finishing for efficient dry or wet cutting. Iscar has introduced two 908, 907 grades of ultra-fine grained carbide substrate plus PVDTiAlN coating. The former has high resistance to plastic deformation and is suitable for drilling inserts and threaded inserts; the latter is suitable for heat resistant alloys, Low and medium speed machining of austenitic stainless steel and hardened steel.

Second, the tool coating technology has made significant progress
Advanced coating equipment has created important conditions for the development of coating technology, especially PVD coating technology, on the one hand, improving control technology, increasing plasma density, increasing magnetic field strength, improving the shape of cathode targets, and realizing the process. The key technologies such as computer automatic control have made comprehensive progress, so that the bonding strength of the coating and the substrate and the performance of the coating are significantly improved. The multi-arc coating process and equipment used by PLATIT and PVT can effectively control the "droplets" generated by the arc, which greatly improves the surface finish of the tool coating. The CC800/9 coating equipment developed by CemeCon uses magnetron sputtering technology to fundamentally avoid the "droplet" problem of multi-arc process. In order to solve the defects of low magnetron sputtering deposition rate and low bonding force, HIS has been developed. (High ionization sputtering) technology, and based on this, developed HIP (High Ionization Pulse) technology, and introduced Supernitrides series coating which can simultaneously have the chemical stability of oxide coating and the physical properties of hard coating. Floor. On the other hand, the coatings are also rapidly expanded from conventional TiN, TiCN, TiAlN to special TiAlN, AlTiN, TiAlCN, CrN, CBC (DLC) coatings and various composite coatings and nano coatings. The composition, percentage, and structure of the coating are controlled and varied over a wider range to accommodate different materials being processed and different cutting conditions, thereby significantly improving the cutting performance of the tool. For example, Balzers' CrAlN coating, which replaces Ti with Cr, has a high performance of 3200Hv hardness and an oxidation temperature of 1100 °C. It has better toughness than TiAlN and is more suitable for interrupted cutting such as milling and hobbing. The nine self-contained coatings developed by Hitachi, in addition to the conventional TiN, TiCN, TiAlN, have also developed a coating that replaces Al with Si, a TiSiN coating for hard cutting, and a CrSiN with lubricity. Coating, adding Si in Cr to make the coating finer to further reduce the friction coefficient, more suitable for processing of highly adherent materials such as aluminum and stainless steel; AlCrSiN coating with superior oxidation resistance and low temperature at high temperature TiBON coating with coefficient of friction. FUTUNANANO and FUTUNATOP, developed by Balzers and used by some tool manufacturers, are two TiAlN nanostructured coatings with a coating hardness of 3300 Hv and an initial oxidation temperature of 900 °C. The development and application of nano-coating will further improve the efficiency of cutting.

At the same time, in order to improve the efficiency of processing non-ferrous metals and non-metallic materials such as aluminum alloys, diamond coatings have been further applied, covering indexable tools and solid carbide tools. Xiamen Golden Heron Special Materials Co., Ltd. developed a diamond-coated solid carbide ball end mill using the imported Balzers equipment. OSG has developed a diamond-coated milling cutter with ultra-fine crystals with a crystal grain size of 1 μm, which makes the cutting edge of the tool sharper, reduces the bonding during cutting, and reduces the roughness of the workpiece surface.

In addition, improving the surface finish of the coating is also a trend in the development of coating technology to improve the resistance of the coating tool to friction and adhesion. In the CVD coating, the surface of the coating is smoothed by grain refining technology. For example, the YBD052 black diamond blade used by Zhuzhou Diamond Company for cast iron finishing has a fine-grained Al2O3 surface, and the blade has a bright and smooth appearance. Mitsubishi's UE series of CVD coated cemented carbide inserts with smooth alumina and smooth coating technology for smooth coating of particulate alumina, ie coating a special titanium oxide layer on the upper layer, smoothing the surface It has good chemical stability and reduces tool bond wear. The GS coating developed by Fujitsu of Japan for GS end mills uses smoothing technology. The surface roughness of the coating is Ra=0.08μm and Rz=1.1μm, which significantly improves the surface characteristics of the coating.

Third, the end mills, taps, drills and other traditional tools enter the stage of high-speed cutting development
For a long time, end mills, taps and drill bits have been used for a wide range of general-purpose tools, mainly made of high-speed steel, and the cutting efficiency is low. In recent years, due to the improvement of the performance of tool materials, especially ultra-fine particle cemented carbide materials, and the popularity of applications, coating technology and CNC grinding technology, the general tool has undergone fundamental changes.

First of all, the performance of the solid carbide milling cutter is doubled, and the cutting speed is increased from less than 100m/min to more than 180m/min. Especially in the aluminum alloy processing of the aerospace industry, the cutting speed is 2000-5000m. /min, with the level of high performance tools. Secondly, the variety of solid carbide tools has increased, covering end mills, twist drills, taps and many other varieties, and the application fields have been further expanded. The third is the widespread application and popularization of CNC tool grinding machines, which has brought about tremendous changes in the structure of the tool. In theory, the five-axis linkage CNC tool grinding machine used by current tool manufacturers can process tools of almost any shape. The geometry, parameters and tool structure of the cutting part of the tool break through the old pattern of the traditional standard tool, and realize the diversified and innovative design that fully reflects the inherent law of the cutting process, so that the potential of the universal tool can be fully explored. This significant advancement in general-purpose tools marks the development of traditional general-purpose tools such as end mills, taps, and drill bits that have entered a new phase of high-speed cutting.

Fourth, the new development of indexable tools
With the rapid development of the manufacturing industry, key industries such as the automotive industry, aerospace industry and mold industry have put forward higher requirements for cutting processing. The application of CAD/CAM technology and CNC numerical control manufacturing technology in tool development and blade pressing Advances in technology have driven the continued development of indexable tools.

In recent years, the indexable tool has been optimized in the structure of the arbor, the reasonable distribution of the cutting load, the development of the three-dimensional chipbreaker of the insert, the development of the spiral blade with a rake angle and the development of a small-sized shallow hole drill. Both have achieved remarkable results. Among them, the progress of the indexable end mill is particularly prominent. For example, the FEEDMILL end mill series developed by Iscar has a new insert shape, a small cutting lead angle and a new clamping structure, so that the feed per tooth can be up to 3.5mm. The way to achieve high metal removal rate, the small lead angle can convert the high-speed feed radial force into axial force, so the longer cavity can be used to extend the deep cavity or outer contour Efficient machining, a gentle transition edge between the primary and secondary cutting edges, which increases the strength of the tool tip and improves the surface roughness of the machine. In order to make the clamping of the blade more reliable, in order to adapt to the large feed amount, a cylindrical protrusion is formed on the bottom surface of the blade, which is matched with the hole of the tool holder during installation, can bear most of the cutting force and reduce the middle clamp. Tightening the load of the screw.

The development of multi-functional composite tools is another trend in the development of current tool structures. In order to take advantage of the CNC machining technology represented by the turning machining center and the boring and milling machining center, the complex parts are processed in a multi-process in one installation, and the conventional cutting, milling, boring, threading and other cutting are diminished. The boundaries of the process are an important way to improve the efficiency of CNC machine tools and speed up product development. To this end, new requirements are also placed on the tool. In addition to the modularity of the tool, a tool is required to complete the processing of different parts of the part as much as possible. Reduce the number of tool changes and save frequent tool change time; at the same time, it can reduce the number of tools and inventory, which is beneficial to management and reduce manufacturing costs. Companies such as Sandvik and Kennametal have developed complete sets of specialized compound tools for the processing of automotive, aerospace engine parts and aircraft components. With the increase of the variety of such tools, structural optimization, geometric parameters are more reasonable, performance is improved, and the application surface is expanding. It not only has new breakthroughs in the applications of turning, milling and drilling, but also expands to broaching and Processing of complex shapes such as gear machining. This type of special high-efficiency tool has become a feature of modern automatic production lines, which plays an important role in reducing investment costs, ensuring production tempo and product quality, and also reflects the close relationship between tools and processes in manufacturing technology, and even the development of new processes and designs. The premise of the new production line.

V. New matching technology for cutting and processing
The cutting technology is an indispensable part of modern cutting technology. It plays an important role in the advancement of cutting technology. It has become a part of modern tool products and keeps pace with the cutting technology and tools. At present, the cutting supporting technology mainly includes the tool holder, the clamping and dynamic balancing of the tool, the use of the tool, the monitoring and management technology.

First of all, in terms of tool systems and tool holders: the application of HSK tool holders is more popular. Various types of tools with HSK tool holders have been widely used in China's automobile industry, aerospace industry, mold manufacturing industry, and gas turbine manufacturing industries. application. At the same time, Nisshin and Dazhao developed three 7:24 joint shanks for contact (3LOCKSYSTEM) and double-sided contact (BIGPLUS), which are more comparable to the existing 7:24 shank. High connection rigidity and precision for high-speed, high-efficiency cutting, and compatibility with existing 7:24 tool holders or machine tools, reducing the cost of new tools and making them practical.

Sandvik's Capto holders have been introduced with the use of tool spindles and OEM-based CNC machine tool manufacturers to take full advantage of the excellent performance of Capto holders in turning center composite machining.

Secondly, in terms of clamping parts: various high-efficiency, high-performance tool chucks are widely used. Foreign tool companies have developed various tool clamping systems such as hydraulic chucks, hot chucks and press-in chucks. For example, Germany's Xiongke Company has developed a three-angle deformation hydrostatic chuck without clamping elements; the PF press-in series of shank developed by Nippon Riken has also achieved end-face contact, and special equipment is used for unloading the knife. The tool was ejected; Sandvik developed the CoroGrip hydraulic drive collet; several companies, such as Biltz and Zoller, developed the hot chuck and heating device, and the new heating chuck device speeds up the cooling and increases the cooling. The working position, and some also added an axially adjustable mechanism, and integrated with the tool setting instrument, which improves the axial precision of the heating chuck.

Third, in terms of tool safety technology: the dynamic balancing technology of the tool has been rapidly developed. The dynamic balance of the tool is an important indicator of high-speed milling tools. For this reason, Germany's HAIMER and Italy's CEMB have developed a special dynamic balancer based on the requirements for tool balancing. Fully automatic tool balance measurement can be realized. The computer screen displays the magnitude, phase and corresponding balance quality level and maximum usage speed of the unbalanced quantity, and can make a plane or two plane imbalance measurement according to the needs. The position of the plane, the unweighted de-weighting position is indicated by the laser beam, and the tool of different tool holders can also be measured by changing the spindle joint.

At present, safety technology has been adopted by the world's famous tool manufacturers. In addition to the high-speed milling cutters introduced by Walter and Mapal in Germany, Toshiba of Toshiba, Japan's DIA9000 processing aluminum alloy milling cutters, Sumitomo Electric Co., Ltd. SUMIDIA diamond milling cutters have been structurally modified to meet the needs of high speed machining. The recommended cutting speed is 3000 to 5000 m/min. The high-speed face milling cutter with a diameter of 3~12in introduced by Valenite Company of the United States has a hardness of 60HRC after surface treatment of the aluminum alloy body, which improves the wear resistance of the cutter body. The dynamic balance of rotary cutters has reached G40 level according to ISO1940/1. The unbalanced quality of some precision high-speed milling cutters has reached G2.5, and the balance is much higher than that of G40. The tool balancing machine can even be balanced to the G1.0 level.

Sixth, the development of CNC cutting technology puts higher requirements on the tool industry
On the one hand, high precision, high efficiency, high reliability and specialization are the basic characteristics of advanced CNC machining technology. The most popular competition slogan of modern tool companies is to provide the most efficient cutting tools for the manufacturing industry. The manufacturing industry also recognizes that reducing labor costs by using high-efficiency tools to increase labor productivity is more beneficial than simply saving tool costs. Therefore, in the field of modern tool manufacturing and use, "efficiency priority" has replaced the traditional "performance price ratio" old concept.

Secondly, modern instrument enterprises are required to have comprehensive high-tech characteristics. The survival and development of modern tool enterprises must be backed by strong research and development capabilities. Under the fundamental goal of improving cutting rate, modern tool enterprises are traditionally processed. The company has gradually developed into a development-oriented enterprise with comprehensive high-tech features including tool basic materials, surface treatment, basic processes and complete sets of services. Its performance is as follows: First, the development and production of new materials for tools has become an integral part of modern tool companies. Second, the development and application of coating technology (PVD and CVD) has become the development of new tools and new materials. The development direction and direction of advanced CNC machining technology has become an indispensable means for modern tool manufacturing to ensure product quality.

One of the important features of modern tool development is specialization, compounding and multi-functionality, resulting in an increasingly complex tool structure and a very specific shape. Conventional tooling techniques—common machine tools and fixtures—can no longer guarantee the spatial positional accuracy between the tool and blade mounting reference and the cutting unit. Therefore, multi-axis linkage CNC machining technology has become an indispensable means for modern tool companies. Due to the particularity of the tool manufacturing process, the special CNC machine tools for tool manufacturing are usually researched and developed by the tool companies themselves, and the machine tool companies cooperate to manufacture them. Therefore, the development and application of tool-specific CNC technology and equipment has become an important work content of modern tool companies. It can be seen that the scope of operation of modern tool companies begins with the research and production of special raw materials, including the development and application of surface treatment technology and special CNC technology and equipment for tool production. The research, production and promotion services of the “three high and one special” tool products have become the focus of enterprise competition. Whoever develops slowly will be eliminated. As a result of this competition, the development of the international tool industry has become increasingly centralized. Those with strong R&D capabilities and economic strength stand out from the competition and become the main force driving and leading the development of the industry. In the manufacturing industry, industries with a wide range of production technology operations are rare.

On the other hand, the depth and breadth of providing comprehensive services to users is increasingly becoming an important indicator of the competitiveness of modern tool companies. In the traditional tool industry production mode, the tool company is only a standard tool production supplier. Many technical problems and management problems in the field are solved by the users themselves. The development of the modern tool industry stage, the role of this server has undergone a major transformation. In order to transfer the new product development costs and management workload to the tool suppliers in part, the foreign manufacturing industry has adopted the platform strategy widely, and the global procurement and integrated management methods have become a trend.

In the procurement of tools, the goal is to shift to countries and regions with low production costs to reduce production costs and increase market competitiveness. In the tool management, the tool factory is transformed from the main tool supply to the main cutting technology, responsible for tool procurement, management and on-site service, the so-called integrated management mode. The tool company provides users with a tool that is not just a tool, but a complete solution to the problem of machining. The two basic elements of this solution are advanced tools and excellent service. Therefore, the ability to provide users with a full range of quality services has become an important indicator of the competitiveness of modern tool companies.