Overview of Electric Built-in Spindles Used in CNC Lathe Tools
1. Electrical Spindle is a New Trend Used in CNC Lathe With Excellent Performance
The machine tool spindle is the axis of motion that drives the tool or workpiece on the machine tool to rotate to produce cutting motion. According to the different ways of the spindle drive, machine tool spindles can be divided into two categories: mechanical spindles and electric spindles.
The components of a mechanical spindle usually consist of a spindle, bearing, and transmission device (including variable speed gear, belt, or coupling), etc. In the CNC lathe machine tool, the spindle is rotated by the spindle motor and the intermediate transmission device to co-work, which is strong in the high output torque and power, but weak in the speed, accuracy, and smoothness.
The high-speed motor of an electric spindle is a built-in design that integrates the spindle function of the machine tool with the motor function. The electric spindle is directly driven by an internal motor and is controlled to obtain the required working speed and torque; thus, it is also called a built-in electric spindle or direct-driven spindle (DDS).
The electric spindle eliminates the need for belts, gears, or couplings, reducing the length of the main drive chain to zero and achieving "zero drive" for the machine tool, effectively improving the overall performance of the spindle at high speeds.
2. Electrical Spindles VS Mechanical Spindles
Thanks to the built-in motor directly driving the electric spindle, the CNC lathe is equipped with electrical spindles which gain the characteristics of compact, light-weight, low noise, low vibration, small rotational inertia, etc. electric spindles can start and stop quickly under high-speed, acceleration, and fixed angle, and the dynamic accuracy and stability are better, which can meet the needs of CNC machine tools for high-speed cutting and precision machining. Since the intermediate speed change and transmission device are eliminated, there is no intermediate transmission link of external force, the dynamic load on the spindle bearing is smaller, and its precision life is extended; the spindle adopts AC frequency conversion and vector control technology, so it can realize infinitely variable speed within the rated speed range to adapt to the needs of various working conditions and load changes during machine tool work.
The electric spindle has a complete function of the "spindle unit", which is independent of the machine tool drive system and the overall structure, which promotes the modularity of the machine tool structure. Spindle manufacturers provide various options of standardized and serialized electric spindles according to the use of machine tools, structure, and performance parameters, which changes the traditional machine tool manufacturers’ "big and complete" production model, shortening the development and production cycle of machine tools. In addition, standardized and serialized electric spindle products are easy to form specialized and large-scale production capacity, thus promoting the reduction of manufacturing costs.
For high-end CNC machine tools such as parallel motion machines, five-sided machining centers, small-hole, and micro-hole machining machines, the process, and workpiece are more special, so there are specific requirements for the spindle speed, accuracy, and the structure of the machine tool. With the integrated structure design and excellent performance of high speed and high precision, the electric spindle effectively realizes the special requirements of certain high-end CNC machine tools.
3. The Application of Electric Spindle Is More And More Popular in The Industry of CNC Lathe Machine Tools
Initially, the imported electric spindles were first used in internal grinding machines, since the 1980s, with the development of CNC machine tools and high-speed cutting technology, electric spindles began to be gradually applied to CNC milling machines, machining centers, and other high-grade CNC machine tools.
Nowadays, China developed a series of high rigidity, high-speed electric spindles and widely used in CNC machine manufacturing and other fields; we shifted from grinding electric spindles to milling electric spindles, which not only can process various shapes of complex parts but also developed air-cooled high-speed milling electric spindles, which promoted the application of high-speed electric spindles in milling.
4. Introduction of core structure and components of electric spindle
The main structure of an electric spindle includes a motor without housing, spindle, bearing, spindle unit housing, drive module, cooling device, etc. From the components, they include spindle assembly, high-speed motor, support parts, cooling system, cylinder assembly, broach assembly, and air seal assembly, and their specific structure and composition vary according to the differences in performance requirements of different applications. The high-speed motor, including the stator and rotor, is one of the core components of the electric spindle drive system, and its role is mainly to drive the spindle core to achieve high-speed rotation. The rotor and spindle of the motor are integrated by means of a press fit, and the spindle is supported by front and rear bearings.
The stator of the motor is mounted in the housing of the spindle unit through a cooling sleeve. The cooling system includes a cooling circulation channel consisting of the body, cooling path, aluminum water jacket and other parts, which is one of the core components of the cooling and cooling part of the electric spindle and is responsible for limiting the temperature rise in the spindle unit.
All the DS series dual-spindle CNC lathe machine tools are equipped with high-performance electric spindles to pursue for high accuracy, high speed, low noise, and low vibration of turning capacity.
