CNC machine tools, CNC cutting tools, and CNC measuring instruments are known as the three pillars of modern machinery manufacturing. CNC machine tools are the main work machines, and CNC cutting tools and CNC measuring instruments are likened to the teeth and eyes of CNC processing. The technological progress of the three pillars promotes the continuous upgrading of modern manufacturing industry in processing accuracy, efficiency and manufacturing methods.
The industry is accustomed to referring to modern and efficient tools with “high precision, high efficiency, high reliability and specialization” as CNC tools. Since the materials of CNC tools generally use high-performance high-speed steel, carbide and super-hard materials, grinding has become the mainstream processing technology of CNC tools, so that the CNC tool grinder as the CNC tool working machine plays a key role. The diversification of CNC tools determines the variety of CNC tool grinders, such as CNC drill bit grinding machines, CNC milling cutter grinding machines, CNC broach grinding machines, CNC hob grinding machines, CNC reamer grinding machines, CNC tap grinding machines, CNC circular saw blade sharpening machines etc. play a unique role in processing corresponding CNC tools. In the past two decades, the advancement of CNC technology such as multi-axis linkage has promoted the rapid development of five-axis CNC tool grinding. Because this machine can sharpen CNC tools of various complex shapes and has versatility and versatility, five-axis CNC tool grinding Tool grinding has become the dazzling star in the CNC tool grinding machine family.
1. Broad market demand
In today’s world, China has become the world’s largest equipment manufacturing country. According to reports, the output value of my country’s equipment manufacturing industry exceeded 20 trillion yuan in 2013, which was 2.2 times that of 2008. It accounted for about one-third of the output value of the global equipment manufacturing industry, firmly ranking first in the world. Among them, the output of power generation equipment is 120 million kilowatts, accounting for about 60% of the world; the shipbuilding completion volume is 45.34 million deadweight tons, accounting for 41% of the world; the output of automobiles is 22.12 million, accounting for 25% of the world; the output of machine tools is 960,000 units, accounting for 38% of the world. . In addition, the annual output of washing machines, refrigerators, motorcycles, air conditioners, televisions, mobile phones, etc. ranks among the top in the world. Machine tools are the main working machines of the equipment manufacturing industry. From 2002 to 2013, my country has become the world’s largest consumer of machine tools for 12 consecutive years. Machine tool consumption accounts for approximately 40%-45% of the total global machine tool consumption. According to relevant statistical data, Figure 2 shows my country’s machine tool consumption from 2005 to 2013.
The rapid increase in demand for CNC tools in my country has given rise to huge market potential for CNC tool grinders. At present, high-end CNC tool grinders mainly rely on imports. It is reported that the number of 4-5-axis CNC tool grinders imported by my country’s main tool manufacturing backbone enterprises has reached more than 100 units, and some medium-sized tool manufacturing companies have also imported dozens of such machine tools. For example, a key tool manufacturing enterprise imported 90 4-5-axis CNC tool grinders at a time in 2012, using foreign exchange of US$44.03 million. In addition to tool manufacturing companies, many machinery manufacturing companies also account for a large proportion of imported 4-5-axis CNC tool grinders due to their own tool grinding and manufacturing needs.
2. Technical characteristics of five-axis CNC tool grinding
Modern five-axis CNC tool grinding is the culmination of CNC machining technology, which is mainly reflected in:
High precision is the embodiment of tool quality, which is directly reflected in the production quality of processed parts. Due to the high precision requirements of modern CNC tools, the corresponding five-axis CNC tool grinding has the nature of a precision machine tool. The machining accuracy of foreign five-axis CNC tool grinding reaches 2μ level, so the machine tool structure is required to be optimally designed, use high-end functional components, and have good static, dynamic and thermal performance.
The main form of CNC tool processing is high-speed, high-precision form grinding. The application of super-hard material grinding tools such as diamond grinding tools and CBN grinding tools puts new requirements on the high-speed performance of grinding machines. For example, the grinding wheel spindle generally uses an electric spindle with a rotation speed of more than 10,000 r/min. ;Requires machine tools to have excellent electromechanical coupling, servo optimization and high acceleration performance. The application of direct drive components such as electric spindles, torque motors, and linear motors has become a new highlight in the high-speed performance of foreign high-end five-axis CNC tool grinding.
Multi-axis linkage control and multi-process compound grinding are one of the main technical features of five-axis CNC tool grinding. Five-axis CNC tool grinding can realize all grinding of complex profiles and composite tools in one installation. Since superhard materials such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PNCB) are used in CNC tools, grinding such CNC tools with diamond grinding wheels seems to be insufficient. Driven by scientific and technological progress, the technology of applying electric discharge grinding and laser processing of CNC tools has emerged, and such machine tools for processing CNC tools have been developed. At present, 5-axis CNC tool grinding is used for rotary electric discharge machining of polycrystalline diamond and integrated grinding wheel grinding in the same tool grinder. It is available in dual-spindle and single-spindle models with electrode and grinding wheel replacement devices. It is mainly used for metal and wood. The processing of polycrystalline diamond tools in processing industries such as , ceramics, and plastics shows that the composite machine tool that uses two-in-one electrical discharge machining and grinding wheel grinding to process PCD tools has also matured. Special processing and composite processing have become important development directions for CNC tool grinding.
The five-axis CNC tool grinder is one of the models with the most intensive application of intelligent technology. Foreign advanced five-axis CNC tool grinding equipment includes laser probes, grinding wheel probes, sonar sensors, CCD cameras, etc. Their models generally have machine tool status monitoring and optimization, dynamic and thermal automatic compensation, anti-collision functions, and tool processing. Functions such as on-machine inspection, online automatic grinding calibration and dynamic balancing of the grinding wheel improve the intelligence level of tool grinding.
“Half is hardware, half is software” This is the basic feature of five-axis CNC tool grinding and processing CNC tools. Without the support of rich CNC tool grinding software, it is impossible to process colorful and diverse CNC tool products. General grinding software includes processing standard tool modules and non-standard tool modules. The operator can use the database or set the tool geometric parameters by himself to form a 3D graphics simulation processing program. For the grinding of complex-shaped tools such as conical ball-nose end mills, powerful foreign companies can currently process them accurately, because processing such tools requires high-precision multi-axis CNC tool grinders and high-precision processing data calculations. Advanced grinding software. It can be seen that the five-axis CNC tool grinding machine is one of the CNC machine tools with the most extensive software development and application.
Robots are widely used in CNC tool grinders, successfully solving problems such as automatic grinding wheel exchange and automatic loading and unloading of workpieces, thus greatly improving the processing efficiency, accuracy and consistency of CNC tool grinders. The organic integration of industrial robots and CNC tool grinding forms an automated grinding center (FMC).
In summary, modern five-axis CNC tool grinding integrates advanced manufacturing technology and has become a carrier of comprehensive application of contemporary high-tech. In addition, five-axis CNC tool grinding can also be used for precision machining of medical parts, complex parts of special materials in the IT industry and aerospace industry. It is foreseeable that the five-axis CNC tool grinding, known as the “elf”, will play an increasingly important role in modern manufacturing.
3. Structural form of five-axis CNC tool grinding
Five-axis CNC tool grinding is mainly used for grinding complex CNC tools. In order to grind complex curved surfaces, machine tool processing requires X, Y, Z, A or (B), C–five-axis linkage. Machine tools generally consist of main moving parts (grinding wheels), feed moving parts, auxiliary parts, columns, machine bases, etc. The layout and structure of the moving parts of the five-axis CNC tool grinding machine are diverse, divided into two categories: discrete type and horizontal type according to the main axis of the workpiece. Now we introduce several types of machine tool structures commonly used at home and abroad.
1. Vertical layout of the axis of the workpiece
As shown in Figure 6, the main axis of the machine tool’s workpiece is arranged vertically to achieve 5-axis linkage:
X—The workpiece table moves laterally
Y—-workpiece worktable moves longitudinally
Z—-The grinding head shaft moves vertically up and down
A—The workpiece spindle rotation angle is 360 degrees
B—grinding head shaft rotation
C—-The workpiece table swings horizontally
Based on this layout, the grinding wheel can approach the workpiece for processing from the front, back, left or right at any angle, achieving 5-axis linkage, and the workpiece can be fully ground in one clamping. This grinding method is flexible and efficient; it eliminates the influence of the center of gravity of the workpiece and achieves high processing accuracy.
2. The axis of the workpiece is horizontally arranged, and the worktable realizes A and C axis rotation.
As shown in Figure 7, the axis of the workpiece is laid out horizontally. The workpiece table has an X axis and realizes A and C axis rotation; the grinding wheel spindle moves up, down, left and right to realize Y and Z axis movement. The column can be of integral gantry type, with the crossbeam sliding up and down the column, and the grinding wheel shaft sliding left and right on the crossbeam. This combination has a compact structure and superior rigidity. The grinding wheel shaft moves smoothly, the workpiece moves stably on the same horizontal plane, and it is easy to operate.
3. The axis of the workpiece is horizontally arranged, the workpiece table rotates on the A-axis, and the grinding wheel spindle rotates on the B-axis
As shown in Figure 8, the axis of the workpiece is laid out horizontally. The workpiece table has an X-axis, a Z-axis and an A-axis, and the grinding wheel spindle has a Y-axis and a B-axis. This combination is more flexible, compact in structure and high in processing efficiency. .
4. The axis of the workpiece is horizontally arranged, and the grinding wheel spindle realizes C-axis rotation.
As shown in Figure 9, the axis of the workpiece is laid out horizontally, the workpiece table has X, Y, Z, A axes, and the grinding wheel spindle has a C axis. This combination increases the stiffness of the C axis and the stability of the grinding wheel operation, improving It improves the movement accuracy of the grinding wheel and is very beneficial for grinding wheel replacement; the workpiece table has many movement coordinates and has a compact structure.
4. Key technologies and important accessories
High-end five-axis linkage CNC tool grinding involves the following key technologies:
⑴ Finite element analysis and complete machine optimization design technology for high-rigidity bed, column and main structural parts of machine tools used for precision grinding; the superior mechanical properties, high vibration reduction, high damping and complex structural design characteristics of high-strength mineral castings , providing the possibility for a high-stiffness lathe bed.
⑵ High-speed electric spindle (grinding head) structural optimization and lubrication and cooling technology;
⑶ High-speed electric spindle grinding wheel virtual online dynamic balancing, detection and dressing technology;
⑷ Rotary axis-A/B/C structural design and high-precision motion technology;
⑸ Linear axis-X/Y/Z design and repetitive positioning accuracy control technology;
⑹ Five-axis linkage tool processing program preparation and system software application technology;
⑺ Automatic tool measurement and positioning system technology;
⑻ High-speed grinding coolant injection and high-pressure and large-flow cutting fluid filtration and cooling technology;
⑼ Final assembly and debugging technology of five-axis linkage CNC tool grinder.
(10) Industrial robot applications and other automation technologies
2. Important accessories
(1) CNC system
High-performance five-axis CNC tool grinding requires a supporting CNC system with the following characteristics: open architecture; high-precision nano-interpolation and motion control; networked fully digital system architecture; efficient surface processing performance; easy CNC programming and debugging wait. The CNC system should have multi-axis, multi-channel control; high-speed, high-precision motion performance; digital bus communication; dynamic compensation, servo optimization and other intelligent functions.
At present, foreign manufacturers generally use FANUC31i system and SIEMENS-840D SL system. This type of control system is highly versatile. Now tool grinder manufacturers are keen to develop special CNC systems and tool grinding software, such as ANCA’s ANCA system, WALTER’s HMC500 and HMC1500/200 systems, and Agathon’s AGATHON system. This trend shows that the dedicated system can increase or decrease the processing functions by modular components according to the complexity of the machine requirements and the processing objects, so as to achieve its versatility and economy. The CNC programming technology of the tool grinder special system combines various mathematical equation expressions, thus enabling a wide range of interpolation: linear interpolation, arc interpolation, involute interpolation, exponential function interpolation, and spiral interpolation Functions such as interpolation and spline function interpolation can solve the high-precision machining of various complex shape tools.
The high-end CNC systems developed by my country Huazhong CNC Co., Ltd., Dalian Guangyang Technology Engineering Co., Ltd., and Changzhou Jieya CNC Technology Co., Ltd. have also been used in conjunction with domestic five-axis CNC tool grinders. Among them, the five-axis grinding machines of Dalian Guangyang and Changzhou Jiaya use mineral castings, a relatively advanced new material at home and abroad, as the bed of their machine tools.
Mineral casting technology has only appeared and developed in Germany for more than thirty years, but currently this technology and products have been widely used in various high-end CNC equipment and other industrial equipment fields around the world, and because of its good performance and Economic efficiency is being applied by more and more customers in more and more fields. With the domestic production and promotion of several German companies that started early in this field, domestic first-class companies of high-end CNC equipment have also tried or are trying to apply mineral castings to their products, and have achieved good market value. and economic benefits.
As China’s mineral casting industry has just started in the past decade or so, some companies have mastered part of the technology and have initially formed a certain market size. But generally speaking, there is still a certain gap with these German companies. They are still in the initial stage of product research and development or market promotion. Mineral casting manufacturers are in a state of blooming technology and uneven performance. For minerals that are in the promotion period themselves, Castings bring certain troubles to customers, and to some extent also hinder the rapid promotion and application of this technology in China.
Compared with ordinary strength mineral casting materials, high-strength composite mineral casting materials are a collective name for a variety of high-strength composite mineral casting materials specially developed by Polystone to meet the needs of customers with high-strength and high-precision mechanical parts. The ingredients of this high-strength mineral casting mainly include quartz stone, rainstone, basalt, fillers, high-performance epoxy resin glue and additives, and special reinforced aggregates. The mixing, stirring, pouring and tamping processes are also significantly different from the manufacturing process of ordinary mineral castings.
(2) CNC tool grinding software
The tool grinding software configured on foreign CNC tool grinders can be divided into two categories: one is software developed by professional tool grinding software companies, such as tool-kit PRO-FESSIONAL developed by Swiss MTS Company, Switzerland The tool grinding software NUMROTOplus developed by NUM Company, etc.; the other type is software independently developed by tool grinder manufacturers. This type of grinding processing software not only includes tool grinder manufacturers (well-known foreign tool grinder manufacturers are usually also well-known tool manufacturer)’s knowledge of tool grinding and machine tool manufacturing is integrated into its long-term accumulated practical experience in tool production. Although the tool grinding processing software launched by various companies differs in functions, intelligence, visualization, etc., they generally have 3D simulation, graphic guidance, parametric programming functions, open tool grinding expert library, etc., to facilitate the realization of CNC Design and manufacture of knives.
Enterprises such as my country’s Huazhong CNC Co., Ltd. and Dalian Guangyang Technology Engineering Company have also developed CNC tool grinding software with independent intellectual property rights.
(3) Functional components
The main functional components include high-performance electric spindle (grinding head spindle), high-precision ball screw and linear rolling guide, high-precision linear grating and circular grating, linear motor and torque motor, and high-precision rolling axis.
Bearings, high-precision CNC turntables, precision hydrostatic bearings, hydrostatic guide rails, etc.
The cutting fluid system of the machine tool needs to be equipped with a high-pressure, high-flow filtration and cooling station. The machine tool is required to be equipped with environmentally friendly safety devices such as oil suction mist, explosion-proof and fire extinguishing.
The intelligent and automated functions of machine tools need to be equipped with automatic measurement and positioning systems for workpieces (tools) and grinding wheels, virtual online dynamic balancing detection devices for grinding wheels, grinding wheel libraries or automatic grinding wheel converters, manipulators, loading and unloading robots, etc., in order to improve the intelligence of machine tools The level of modernization and automation meets the growing demand for efficient and high-precision grinding of CNC tools.
5. Introduction to typical foreign products
1.WALTER Helitronic Power type tool grinder
As shown in Figure 10, this model has a horizontal layout of the workpiece axis, a gantry column structure, a workpiece table with an X axis, and realizes A and C axis rotation; the grinding wheel spindle moves up, down, left and right to realize the Y and Z axes. One-time clamping can realize the grinding of complex rotary CNC tools with a diameter of 3-320mm and a length of 350mm. The machine is equipped with FANUC31i CNC system, and the company develops its own CNC tool grinding software. The machine tool can be equipped with an electric spindle grinding wheel, a torque motor turntable, an automatic tool positioning probe, an automatic grinding wheel replacement device, a tool online profile measuring instrument, an automatic tool support frame, an automatic tool loading and unloading device, etc. Options include: feed rate optimizer, tool balancer, integrated measurement system, torque adaptive control, etc.
2. Australian ANCA Company MX5 five-axis CNC tool grinder
This model has a horizontal layout of the axis of the workpiece to be processed, a gantry column structure, and adopts the ANCA CNC CONTROL control system to realize X, Y, Z, A, C-five-axis linkage. X/Y/Z—540/510/215mm, C/A—264°/360°, main power 14kW; the machine tool has 2 sets of grinding wheel frame systems, the grinding wheel shaft speed is 10000r/min, and the exchange time is 10s , the maximum diameter of the grinding wheel is 203mm; equipped with a laser continuous measurement system and a robot loading and unloading system. The diameter of the workpiece to be processed is 100mm, the processing length is 300mm, and it has self-developed 3D simulation grinding software.
6. Suggestions on accelerating the development of domestic high-end five-axis CNC tool grinding
Overall, compared with foreign advanced levels, domestic five-axis CNC tool grinding has gaps in processing accuracy, efficiency, intelligence, automation, CNC and software technology, reliability and pleasantness. Accelerate the development of domestic high-end five-axis CNC tool grinding. Tool grinding requires the support of national industrial policies and science and technology policies, and it also requires the efforts of the industry. To this end, the following suggestions are made:
(1) Increase the support for the scientific research, development, demonstration and promotion of five-axis CNC tool grinding by the national major science and technology project “High-end CNC Machine Tools and Basic Manufacturing Equipment”.
(2) Focus on improving the technical level, product quality and reliability of domestic five-axis tool grinding. Many well-known five-axis grinder manufacturers at home and abroad have chosen the KL600 formula of Polystone Equipment Technology (Suzhou) Co., Ltd., which masters core key technologies in the field of mineral castings, as their mature four-axis and five-axis grinder products or are currently developing them. The product’s machine tool bed has taken the lead in technology and achieved fruitful results that exceeded expectations.
(3) Vigorously develop the functional components required for five-axis CNC tool grinding products to provide supporting industry chain support for product upgrading and industrialization.
(4) Support key key enterprises to implement technological transformation and improve the level of five-axis CNC tool grinding manufacturing process equipment and testing and testing capabilities.
(5) Encourage key enterprises to take the lead, market demand as the traction, and the integration of “industry, academia, research and application”. In particular, we must strengthen the cooperation between leading enterprises in the two industries of tool manufacturing and tool grinder manufacturing to promote the industrialization of scientific and technological achievements.
“If a worker wants to do his job well, he must first sharpen his tools.” Promoting domestic five-axis CNC tool grinding to improve the technical level and industrialization level, accelerating the development of domestic high-end five-axis CNC tool grinding, and meeting the needs of my country’s manufacturing industry have become urgent tasks for the transformation and upgrading of the machine tool industry. We call on powerful enterprises and people with lofty ideals to work hard and contribute to accelerating the development of domestic high-end five-axis CNC tool grinding.
As a latecomer in this field, Polystone adheres to the mature technology foundation and rigorous work philosophy originated from Germany, and continuously increases investment in funds, talents, research and development, technology, etc., making the company quickly become a company that can meet the needs of One of the companies with high demand for high-performance mineral casting products from domestic and foreign customers. Polystone has developed 8 different product formulas ranging from KL200 to KL1000 based on the actual uses of customers. All of them have been tested by professional testing institutions within the company or third parties, and all of them comply with German DIN standards. Among them, the physical properties of formulas above KL600 have been close to or reached the same technical indicators as natural marble. At the same time, they have the unique characteristics of high vibration reduction, high damping coefficient, acid and alkali resistance, and easy structural design of mineral casting materials. Ideal material for axis CNC tool grinder beds.