With the rapid advancement of high-tech industries such as defense, aerospace, automotive, and microelectronics, the manufacturing sector is facing increasingly stringent demands. Ultra-high-speed machining and ultra-precision machining have emerged as key focuses for the future development of machine tools. Traditionally, the feed drive system in machine tools has relied on a "rotary motor + ball screw" mechanism. However, this system involves multiple intermediate components, leading to significant motion inertia and physical limitations in terms of speed, acceleration, and positioning accuracy. As a result, it struggles to meet the needs of modern high-speed and high-precision machining.
Linear motors have gained significant attention due to their direct linear motion capability, simplified structure, reduced inertia, high stiffness, and excellent fast response characteristics. They offer precise high-speed positioning and higher thrust compared to ball screws, with significantly greater speed and acceleration. Additionally, they provide infinite travel and require less maintenance, making them an ideal choice for modern machine tool feed systems.
In machine tool applications, the primary technical challenges for AC linear motors in servo systems include heat management, magnetic shielding, and guide rail performance. Permanent magnet linear motors generate heat from copper and iron losses during operation, which can damage insulation, alter magnet performance, and cause thermal deformation in the machine table or guideways. Cooling is essential, especially for large thrust flat-plate motors, where temperatures must be kept below 70°C for magnets and 130°C for coils. Special cooling methods, such as double-layer water cooling with temperature monitoring, are necessary for ultra-precision applications.
Magnetic isolation is also critical, as cutting fluids, metal shavings, and dust can interfere with motor performance. The motor must be enclosed, and permanent magnets should be shielded using stainless steel covers to prevent unwanted attraction. Shock-absorbing devices and electronic limit switches are required at both ends of the motor to prevent uncontrolled collisions. Cables should also be shielded to avoid damage from external forces.
The linear guide rails must support heavy loads, accommodate high-speed movement, and maintain precision. Rolling linear guides are commonly used to ensure parallelism, while aerostatic guides may be employed for ultra-precision requirements.
As the manufacturing process of linear motors advances, production scales expand, and the cost of permanent magnets and electronics declines, the price of linear motors is dropping by about 20% annually. This trend promises broad application potential in machine tools. Although still a relatively new technology, both the motors themselves and the associated CNC systems hold great promise. As a major manufacturing country, China has a long journey ahead in developing high-end CNC equipment.
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