Application and Development of Linear Motor in the Manufacturing Technology and Equipment Industry of the World
time£º2010/9/4 click£º8470
1, overview
Linear and rotation are the two main modes of movement in the world. Many linear driving devices or systems often use rotary motors to convert into linear motion through intermediate conversion devices such as chains, wire ropes, belts, teeth, or rods. Because these devices or systems have intermediate conversion transmission mechanisms, the entire mechanism is often more complex, larger in size, and the speed and accuracy can not further meet people's higher requirements. Linear motor is a kind of transmission that converts electrical energy into linear motion mechanical energy without any intermediate conversion mechanism. It has simple structure, no contact operation, low noise, high speed and accuracy, easy control, convenient maintenance, and high reliability. advantage. It is a new technology with new principles and new theories in the field of electricity since the second half of the 20th century. At present, linear motor technology has been widely used in various linear driving devices and systems, such as high-speed maglev trains, maglev boats, various logistics transmission lines, and various automated equipment such as plotter, printer, copier, and scanner. All kinds of civilian and military equipment, especially in the industrial manufacturing technology and equipment industry, have applied linear Motors more widely and prominently, especially in recent years. The advantages of simple structure, no contact, high speed, easy control and high precision of linear motor further promote its development and application in this field. In foreign countries, the application of linear motor in the machine response bed industry has even become a "hot spot" and has received widespread attention.
Application and Development of Linear Motor in Foreign Manufacturing Equipment Industry
2.1. Advantages of Linear Motor in Machine Tool
The application of linear motor in the overseas manufacturing equipment industry is first in the machine tool equipment. The driving device of traditional machine tools depends on the drive of the wire rod, and the wire rod drive itself has a series of unfavorable factors. Including: length limit, mechanical back gap, friction, distortion, pitch one-cycle error, longer vibration attenuation time, coupling inertia with the motor, and axial compression of the wire bar. All these factors limit the efficiency and precision of the traditional drive device. When the equipment is worn, it must be constantly adjusted to ensure the required accuracy. Linear motor drive technology can ensure a very high performance level and higher simplicity than the traditional motor drive device that converts rotation into linear motion. Since the linear motor is directly connected to the moving load, there is no back gap between the motor and the load, and the flexibility is small.
The use of a linear drive device can reach a speed of less than 1 ¦Ìm/s or up to 5 m/s in large capacity. The linear drive system can ensure a constant speed characteristic, and the speed deviation is better than ¡À 0.01 %. In applications that require higher acceleration, smaller linear motors can easily provide acceleration greater than 10g, while conventional motors generally produce acceleration in the range of 1G. The precision of linear drive motor is limited only by feedback resolution, control algorithm and motor structure. The linear motor system with feedforward control can reduce the tracking error by more than 200 times, while the traditional driving system is constrained by the aforementioned factors and is also limited by the mechanical system.
The linear motor has a simple structure and consists of very few components, so less lubrication is required(the linear rail needs regular lubrication). This means that it has a long service life and is relatively clean to run. In contrast, the traditional drive system consists of more than 20 parts, including Motors, couplers, ball bars, U-shaped blocks, bearings, pillow blocks, and lubrication systems. Each component requires assembly time, adjustment time and preventive maintenance. In contrast, the linear motor structure is very simple. It is an electromagnetic actuator. The actuator consists of two rigid parts supported on a linear guide rail.
Other advantages of linear Motors include lower force and smaller speed ripples to ensure a smoother motion profile. Of course, this depends on the structure of the motor, the magnetic plate, and the driving software. In order to take advantage of the inherent dynamic braking of the linear motor, the drive amplifier should effectively monitor the inverse electromotive force(EMF), even if the system power supply may be turned off. Multiple linear motors can be installed "back to back" to ensure increased force. Additional magnetic plates can also be added to ensure substantial extended trips(limited by feedback devices and cable lengths) without losing precision.
Jean-Paul Bugaud, engineering director of Renault Automation of France, believes that "the linear motor has become more and more mature, and its accuracy is by no means comparable to that of a ball-driven machine tool. After two or three years, it will be a standard choice in high-precision and high-precision processing. The temperature changes are no longer worrying, and they can get the same accuracy at 10 ¡ãC or 40 ¡ãC. A few years later, it is estimated that in addition to cheap machine tools, ball rods will no longer be used.
2.2. Application of Linear Motor in Machine Tool Equipment
As early as 1996, SODICK of Japan began to use linear motors on EDM generators to develop dedicated linear motors and NC systems that match linear Motors. The linear servo system composed of linear servo motor as the driving element was first developed and applied to the EDM, and then rapidly expanded to the EDM cutter. It was put on the market in 1999. The system has new features to enter the network. The models they introduced are AM55L(2-axis linear motor) and AQ351(X, Y, Z three-axis linear motor). This linear motor servo system has significantly improved the processing performance. Its characteristics are:
(1) Change the linear motion previously realized by the rotation of the rotating motor into a direct linear motion of the shaft, eliminating the need for the screw transmission link and ensuring the high-speed movement of the shaft. The axis movement speed can be reached at 36m/min at a control equivalent of 0.1 ¦Ìm. Compared with the original control method, the axis movement speed can be increased several times to dozens of times. The high-speed movement of the Z axis can realize the rapid jump of the electrodes during the process, so that the fluid force in the discharge gap increases, the debris is sufficient, the processing conditions are improved, and the discharge utilization rate is improved. In the absence of flushing, Get higher processing speed. For example, a graphite sheet electrode with a section size of 1mm X 38mm and an electrode taper of 1 "is used to process steel using a deep narrow cavity treated with a fast jump non-impulse liquid. The cavity depth is 70mm and the total processing time is 3 hours. 40 minutes, Among them, the rough processing time is 2 hours and 10 minutes, and the finishing processing time is 1 hour and 30 minutes. The surface roughness after processing Ramax 10 ¦Ìm; The traditional processing method is used to process 40mm deep in 2 hours and can no longer be processed. It is proved that the advantages are obvious in small cavity processing.
(2) The linear motor servo system adopts the structure of the linear motor and the slide board. The displacement of the slide plate is the direct movement of the linear motor. There is no link between the two, which eliminates the mechanical response lag phenomenon in the middle link. Therefore, the dynamic response time of linear motor is reduced by an order of magnitude compared with the traditional AC DC motor with ball screw system. The high response speed can improve the sensitivity of the servo system to ensure the stability of the processing.
(3) The motion mode of the linear motor servo system determines that the servo unit must use the linear position feedback element as the position detection link, and the control and drive is a fully closed-loop system that directly detects the linear displacement of the slip plate. There are no factors such as screw pitch error and wear of transmission chain parts, which leads to the use of rolling rails with faster response speed. Therefore, it is more conducive to achieving precision positioning control and improving the accuracy retention of machine tools.
(4) Due to the greater force of the machine tool during rapid jump, compared with traditional machine tools, the stiffness of the machine tool must be increased and the structure of the machine tool must be changed to meet the needs of high-speed linear servo movement. In addition to improving the stiffness of the machine tool, the NCEDM driven by Sadik's linear servo motor also uses a sliding pillow structure with fixed worktables and X, Y, and Z axes on the columns.
(5) To avoid the impact of magnetic fields, the slide is made of ceramic materials. Permanent magnets(armature) are installed on both sides of the slide and fixed on both sides of the main shaft.
Linear motor