Development and prospect of high speed cutting technology

Machining is one of the most widely used machining methods in machining, and high speed is an important development direction, including high-speed soft cutting, high-speed hard cutting, high-speed dry cutting, and large feed cutting. High-speed cutting can greatly improve production efficiency and material removal rate per unit time, improve processing surface quality and reduce processing costs.

1 High-speed cutting concept and high-speed cutting technology

High-speed cutting is a relative concept, how to define it, there is no consensus at present. Moreover, due to different machining methods and different workpieces with different high-speed cutting ranges, it is difficult to give a precise definition of the speed range of high-speed cutting.

High-speed cutting technology is in machine tool structure and materials, machine tool design and manufacturing technology, high-speed spindle system, rapid feed system, high-performance CNC control system, high-performance toolholder system, high-performance tool material and tool design and manufacturing technology, high-efficiency and high-precision measurement. Test technology, high-speed cutting mechanism, high-speed cutting technology and many other related hardware and software technologies have been fully developed on the basis of comprehensive development. Therefore, high-speed machining is a complex system engineering involving machine tools, tools, workpieces, machining process parameters and cutting mechanisms.

2 High-speed cutting technology abroad development status

Since Dr. Carl. J. Salomon of Germany proposed the concept of high-speed cutting and applied for a patent in the same year, the development of high-speed cutting technology has experienced the theoretical exploration stage of high-speed cutting, the exploration stage of high-speed cutting application, the preliminary application stage of high-speed cutting, and high-speed cutting. The four stages, such as the more mature stage, have been promoted and applied in production. Especially since the 1980s, various industrialized countries have invested a lot of manpower and financial resources, researching and developing high-speed cutting technology and related technologies, and developing rapidly.

In recent years, high-speed processing machine tools have developed rapidly in the United States, and the United States, France, Germany, Japan, Switzerland, the United Kingdom, Canada, Italy and other countries have developed their own high-speed cutting machine tools. High-speed spindle is the most important key technology of high-speed cutting technology. It usually adopts the main shaft and motor integrated electric spindle components to realize direct transmission without intermediate links. The main shaft supports generally use ceramic bearings, hydrostatic bearings, dynamic pressure bearings, air bearings and Oil 0 gas lubrication, spray lubrication and other technologies, also use magnetic bearings. The feed system starts with a linear motor or small lead large-size high-quality ball screw or large lead multi-head screw to provide higher feed speed and better acceleration and deceleration characteristics. The maximum acceleration is up to 2 ~10g. The CNC control system uses multiple 32-bit or 64-bit CPUs to meet the requirements of high-speed machining for fast data processing, and uses feedforward and a large number of advanced block processing functions to ensure interpolation accuracy during high-speed machining. A powerful high pressure, efficient cooling system is used to solve the extremely hot chip problem. Temperature-controlled circulating water (or other medium) is used to cool spindle motors, spindle bearings, linear motors, hydraulic tanks, electrical cabinets, and some even cool large components such as headstocks, beams, and beds. Take more complete safety measures to ensure the safety of machine operators and on-site personnel around the machine, avoid damage to machine tools, tools, workpieces and related facilities; identify and avoid working conditions that may cause major accidents; ensure product output and quality.

Studying the influence of the material properties of the workpiece on the processing method, some difficult-to-machine materials such as nickel-based alloys, titanium alloys and fiber reinforced plastics become easy to cut at high speeds. In addition, the optimum cutting speed of different materials is also different. The workpiece material is also an important basis for selecting tools and processing parameters. Generally, in high-speed machining, high speed, medium and small depth of cut, fast feed, multi-stroke, but high-speed machining are recommended. In terms of process parameter selection, there is currently no database for production and practical use in the world.

The research on high-speed cutting mechanism mainly includes the chip forming mechanism, cutting force, cutting heat variation law and the influence of tool wear mechanism on machining efficiency, machining precision and machining surface integrity during high-speed cutting. At present, the research on the high-speed cutting mechanism of aluminum alloy has reached a relatively mature conclusion, and has been used to guide the high-speed cutting production practice of aluminum alloy. However, the research on the high-speed cutting mechanism of ferrous metals and difficult-to-machine materials is still in the exploration stage. The high-speed cutting process specification is still not perfect. It is a difficult point in high-speed cutting production and the focus of research in the field of cutting processing. In addition, high-speed cutting has entered the application of reaming, tapping, etc., and its mechanism is constantly being studied. At present, more research and discussion on the cutting force, cutting temperature, tool wear and tool life, machining surface quality and machining accuracy during high-speed cutting are needed.

3 Domestic development status of high-speed cutting technology

The research and application of high-speed cutting in China started late, but it has attracted widespread attention since the 1990s. At present, there are more than 3 million machine tools in the country, most of which are general-purpose machine tools. CNC machine tools, including economic models, account for about 10%, and import CNC machine tools and machining centers in aviation, aerospace, automotive, mold, machine tools and engineering machinery. Accounted for a large proportion. At present, the vertical machining center of 10000~15000r/min and the horizontal machining center of 18000r/min have been successfully developed and produced. The high-speed digital copy milling machine produced has a maximum speed of 40,000r/min and a numerical control of 3500~4000r/min. Lathes and turning centers have been produced in batches, and 8000r/min CNC lathes have also been introduced. High-end CNC systems and open CNC systems for high-speed machine tools are under in-depth research, but they are still mainly imported. At present, China is gradually promoting the application of high-speed cutting technology, mainly in the aerospace, mold and automotive industries, processing more aluminum alloys and cast iron, but the tools used are mainly imported.

Domestic tool materials are still dominated by high-speed steel and carbide tools. Advanced tool materials (such as coated carbide, cermet, ceramic tools, CBN and PCD tools, etc.) have a certain foundation, but the application range is not wide enough. In general, the cutting speed is generally low, and the cutting level and processing efficiency are low. The basic theory research of high-speed cutting started late. Since the 1980s, the domestic research on the chip formation, cutting temperature, cutting force, tool wear and damage, tool life and surface quality of ceramic cutting tools during high-speed hard cutting has been systematically studied. More applications have been made in production. Since the 1990s, the cutting force, cutting temperature, tool wear and damage and tool life of high-speed cutting aluminum alloy, steel, cast iron, superalloy, titanium alloy, etc. have been studied and discussed, but no comprehensive systematic research has been conducted. . There are many researches on the monitoring technology of the cutting process, but it is less used in production.