High-speed machining technology has some advantages, such as high production efficiency, high processing precision and low processing cost. In recent years, it has received wide attention and is regarded as one of the most promising advanced manufacturing technologies in the 21st century. Following the CNC machining technology, high-speed machining technology is making another major change in the manufacturing sector, and will influence the development trend of future industrial production. To achieve high speed machining, having a higher cutting speed is an indispensable prerequisite. The high-speed electric spindle that provides the driving force for high-speed cutting tools plays the most important role. As the core functional component of the whole high-speed machining technology, we often use high-speed electric spindles in modern CNC machine tools.
What is high-speed electric spindle technology?
High-speed electric spindle technology is a new technology that integrates the spindle part of the CNC machine tool with the spindle motor by directly using the rotor of the motor as the spindle of the machine tool. In actual work, the hollow motor rotor is directly mounted on the main shaft, and the stator is fixed in the hole of the main shaft box through the cooling sleeve to form a complete spindle unit, and the rear rotor drives the main shaft to run. The spindle does not need any mechanical connection, which realizes the “zero transmission” of the machine tool. As long as the power supply frequency is changed, the spindle speed can be realized.
Compared with the traditional machine tool spindle, the electric spindle is more compact and lighter in weight. It has higher speed, higher power, faster response speed and lower noise than conventional spindles. This unitized structure greatly simplifies the design of the machine tool and is easy to position. It is an ideal structure. In the field of CNC machine tools, this technology, together with linear motor technology and high-speed tool technology, has pushed high-speed machining process water to a new level.
China's research on the use of CNC machine tool electric spindle started in 1998. At present, there is still a certain gap with foreign advanced technology, and mass production scale has not yet been formed.
Application of high-speed electric spindle
High-speed electric spindles are very strict with their bearings and motor performance. Bearings need to have good rigidity, damping resistance and long service life. There are usually three options: dynamic and static bearings, composite ceramic bearings or electromagnetic suspension bearings. Among them, the composite ceramic bearing uses hot-pressed ceramic ball and steel bearing ring, because of its heat and wear resistance, high standardization and easy maintenance, it is most widely used in the electric spindle unit. Although the electromagnetic suspension bearing has high speed performance, high precision and easy display and monitoring, the structure and system are too complicated, the manufacturing cost is high, and the price is high for a long time, so it has not been widely promoted.
Because it is integrated with the motor, the electric spindle itself can also be regarded as a high-speed motor. There are many different forms of structure, such as induction motor, permanent magnet motor and reluctance motor. The key technology is high speed. Dynamic balance.
Main parts of electric spindle
A complete set of electric spindle system, in addition to the spindle itself, should also include the main related accessories such as high frequency inverter, oil mist lubricator, cooling device, built-in pulse encoder and tool changer.
High-frequency inverter device:
To increase the machining speed, it is necessary to ensure the high-speed rotation of the electric spindle, thus driving the cutting tool to run at high speed. There is a need for a device to act as a drive for the built-in high-speed motor of the electric spindle, so that its speed reaches tens of thousands or even hundreds of thousands of times per minute. The role of the high-frequency inverter device is here. In order to achieve the goal, the output frequency of the high frequency inverter must reach several kilohertz or more.
Oil mist lubricator:
Good lubrication can reduce the resistance, wear and heat of the equipment. The lubrication of the electric spindle needs to strictly follow the principle of timed quantification, that is, to fill the bearing once every fixed period of time. When oil is injected, the lubricating oil is blown into the bearing in the form of oil mist under the carrying of compressed air. The amount of oil injected is precisely controlled by the dosing valve, and too much or too little will have an adverse effect.
Cooling device:
If the temperature of the electric spindle is too high during operation, it will cause damage to the equipment. In order to dissipate heat from the high-speed electric spindle and reduce the working temperature as soon as possible, it is usually necessary to use circulating coolant. The circulating coolant acts on the outer wall of the electric spindle and takes away part of the heat from the electric spindle. However, if the temperature rises after the coolant absorbs heat, it will not be cooled. The existence of the cooling device is to maintain the original temperature of the coolant and enhance the cooling effect.
Built-in pulse encoder:
This is a position detection component using the principle of optical sensor for non-contact detection. The encoder disc is mounted on the rotating shaft of the motor. During the rotation, the angle, position and speed of the shaft rotation will be automatically measured, and the detection result will be output as an electric pulse. The advantage of this type of detection is that there is no friction and wear, only a small driving force is required, but the most accurate detection result and the fastest response speed can be obtained, so that the accurate rotation phase angle control of the electric spindle and the feed can be realized. Cooperate.
Automatic tool changer:
In order to achieve flexible adaptation and quick response to various processing materials and processes, the electric spindle is equipped with an automatic tool changer, which can automatically select the most efficient and reasonable cutting equipment according to different situations. The automatic tool changer is composed of a disc spring, a broach cylinder and the like. It has been proved by practice that high-speed tools such as HSK and SKI are more suitable for high-speed machining.
If high-speed processing equipment is far more than the processing speed of traditional processing equipment, it is called the “sportsman” in modern manufacturing. Then, the high-speed electric spindle is undoubtedly the heart of this “sportsman”. To be a powerful driving force. The improvement of high-speed electric spindle technology is a key part of realizing the high-speed and precise revolution of the manufacturing industry. It is an important symbol of the industrial manufacturing water products keeping up with the times and must be taken seriously by us.
