CNC machine tools are developing in the direction of precision, high speed, compound, intelligence and environmental protection. Precision and high speed machining puts higher demands on the drive and its control, higher dynamic characteristics and control accuracy, higher feed rate and acceleration, lower vibration noise and less wear. The crux of the problem is that the traditional transmission chain from the motor as the power source to the working parts through the gears, worm gears, belts, screws, couplings, clutches and other intermediate transmission links, in these links produced a large rotational inertia, elastic deformation, backlash, motion hysteresis, friction, vibration, noise and wear. Although in these areas through continuous improvement to improve the transmission performance, but the problem is difficult to fundamentally solve, in the emergence of the concept of “direct transmission”, that is, the elimination of various intermediate links from the motor to the working parts. With the development of motors and their drive control technology, electric spindles, linear motors, torque motors and the increasing maturity of the technology, so that the spindle, linear and rotary coordinate motion of the “direct drive” concept into reality, and increasingly show its great superiority. Linear motor and its drive control technology in the machine tool feed drive on the application, so that the machine tool transmission structure has been a major change and make a new leap in machine performance.
The Main Advantages of Linear Motor Feed Drive:
Wide range of feed speeds:Can be from 1 (1) m / s to more than 20m / min, the current machining center fast-forward speed has reached 208m / min, while the traditional machine tool fast-forward speed <60m / min, generally 20 ~ 30m / min.
Good speed characteristics:Speed deviation can reach (1) 0.01% or less.
Large acceleration : Linear motor maximum acceleration up to 30g, the current machining center feed acceleration has reached 3.24g, laser processing machine feed acceleration has reached 5g, while the traditional machine tool feed acceleration in 1g or less, generally 0.3g.
High positioning accuracy : The use of grating closed-loop control, positioning accuracy up to 0.1 ~ 0.01 (1) mm. the application of feed-forward control of linear motor drive system can reduce tracking errors by more than 200 times. Due to the good dynamic characteristics of moving parts and sensitive response, coupled with the refinement of interpolation control, nano-level control can be achieved.
Travel is not limited : The traditional ball screw drive is limited by the manufacturing process of the screw, generally 4 to 6m, and more strokes need to connect the long screw, both from the manufacturing process and in the performance is not ideal. The use of linear motor drive, the stator can be infinitely longer, and the manufacturing process is simple, there are large high-speed machining center X-axis up to 40m long or more.
Progress of Linear Motor and Its Drive Control Technology:
Linear motors are similar to ordinary motors in principle, it is only the expansion of the cylindrical surface of the motor, and its types are the same as traditional motors, such as: DC linear motors, AC permanent magnet synchronous linear motors, AC induction asynchronous linear motors, stepper linear motors, etc.
As a linear servo motor that can control the accuracy of motion appeared in the late 1980s, with the development of materials (such as permanent magnet materials), power devices, control technology and sensing technology, the performance of linear servo motors continue to improve, the cost is decreasing, creating the conditions for their widespread application.
In recent years, the linear motor and its drive control technology progress in the following areas: (1) performance continues to improve (such as thrust, speed, acceleration, resolution, etc.); (2) volume reduction, temperature reduction; (3) a wide variety of coverage to meet the requirements of different types of machine tools; (4) a significant drop in cost; (5) easy installation and protection; (6) good reliability; (7) including CNC systems In the supporting technology is becoming more and more perfect; (8) high degree of commercialization.
At present, the world’s leading suppliers of linear servo motors and their drive systems are: Siemens;Japan FANUC, Mitsubishi; Anorad Co.(USA), Kollmorgen Co.; ETEL Co. (Switzerland) etc.
Post time: Nov-17-2022
