Application and development trend of the hottest l

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Application and development trend of linear motor in CNC machine tools

1. Introduction

CNC machine tools are developing towards precision, high speed, compound, intelligent and environmental protection. Precision and high-speed machining put forward higher requirements for transmission and control, higher dynamic characteristics and control accuracy, higher feed speed and acceleration accuracy up to 0.01%, lower vibration noise and less wear. The crux of the problem lies in the fact that the traditional transmission chain, from the motor as the power source to the working parts, passes through the intermediate transmission links such as gears, worm gear pairs, belts, lead screw pairs, couplings and clutches. In these links, there are large moments of inertia, elastic deformation, reverse clearance, motion lag, friction, vibration and noise, including the main module of the experimental program, the experimental parameter setting module, the database management module, the report printing module Sensor calibration module and wear. Although the transmission performance has been improved through continuous improvement in these aspects, it is difficult to fundamentally solve the problem. Therefore, the concept of "direct transmission" has emerged, that is, various intermediate links from the motor to the working parts have been eliminated. With the development of motor and its drive control technology, the emergence of motorized spindle, linear motor and torque motor and the growing maturity of technology, the concept of "direct transmission" of spindle, linear and rotating coordinate motion has become a reality, and increasingly shows its great advantages. The application of linear motor and its drive control technology in the feed drive of machine tools has greatly changed the transmission structure of machine tools and made a new leap in the performance of machine tools

II. Main advantages of linear motor feed drive

· wide range of feed speed. It can range from 1 (1) m/s to more than 20m/min. At present, the fast forward speed of the machining center has reached 208m/min, while the fast forward speed of the traditional machine tools. The main features of the manufacturers of machine types and models are the EDM machine tool gv754l. The fast forward speed of the Beijing Machine Tool Research Institute is 24m/min

the acceleration is 1.5g. The vertical machining center vs1250 is the x/y axis linear motor of the high tech

joint stock company of Beijing Institute of mechanical and electrical engineering,

fast forward 80/120m/min

acceleration 0.8/1.5g vertical machining center xh716/5x-sm Jiangsu duoling CNC Machine Tool Co., Ltd. X-axis linear motor turning and Milling Center Shenyang Machine Tool Group X-axis linear motor,

fast forward 60m/min Piston Lathe g-cncp200 Tsinghua University X-axis linear motor cam grinder Beijing University of Aeronautics and Astronautics head frame drive linear motor,

accuracy is improved, and there is no ripple

at present, Almost all the world's most famous machine tool manufacturers have launched linear motor driven machine tool products, covering the vast majority of machine tool types. In addition, linear motors are used in press, coordinate measuring machine, water cutting machine, plasma cutting machine, rapid prototyping machine and X-Y workbench of semiconductor equipment

in addition, the Institute of linear motor and modern drive of Zhejiang University has developed linear motor driven presses, sawing machines, engraving machines and wire cutting machines

high speed vertical machining center driven by linear motor, a key project of the Tenth Five Year Plan undertaken by Beijing Institute of mechanical and Electrical Technology Co., Ltd., successfully developed the first linear motor driven machining center in China in 2003, and was exhibited at the 2003 Beijing International Machine Tool Exhibition. The x/y axis of the machine tool is driven by linear motor. The stroke is 1250/630mm, the maximum fast moving speed is 80/120m/min, and the maximum acceleration is 0.8/1.5g. In the design of the machine tool, useful explorations have been made in reducing the mass of moving parts, strengthening the rigidity of the machine tool, solving the impact resistance under high-speed and high acceleration motion, protecting the linear motor, and matching, optimizing and debugging the control system, servo system and linear motor, and achieved success. In order to solve the protection problem of y-axis linear motor under the workbench, a sealed linear drive shaft component was designed and obtained a national patent. Through measurement, the accuracy of the machine tool reaches the standard of precision machining center, and there is sufficient margin. The machine has been working stably and reliably for more than a year. The research group also tested the temperature rise of the primary coil and secondary magnet (stator) of the linear motor. Take axis X as an example: the mass of moving parts of axis X is>1000kg, the acceleration is set as o.8g, the fast moving speed is set as 70m/min, and the continuous reciprocating motion is more than 1 hour. Test results: after 10 minutes, the temperature rise of primary coil (water cooling) tends to be balanced, and the working temperature is stable at about 69 ℃, which is far lower than the allowable working temperature (12 ℃). The temperature of the secondary magnet of the motor has the following requirements for the friction coefficient experiment: about 2 ℃. It can be seen that the temperature rise of the primary coil and secondary magnet (stator) of the linear motor has limited thermal impact on the machine tool, which can be eliminated by compensation

Figure 2 machining center driven by vs1250 linear motor

v. development trend

1) technology is becoming more and more mature

linear motor and its drive control system have become more and more mature in technology, and have superior performance that traditional transmission devices can not compare. With the improvement of motor manufacturing technology, the problems that people worried about in the past, such as small thrust, large volume, high temperature, poor reliability, insecurity, difficult installation, difficult protection, are no longer a prominent flame retardant problem. The development of drive and control technology provides a guarantee for its performance expansion and safety. Choosing the appropriate linear motor and drive control system, coupled with a reasonable machine tool design, can produce high-performance, high reliability machine tools. At present, it is common for linear motors to drive machine tools with a feed speed of 100m/min and an acceleration of 1 ~ 2G. Some machine tools have reached the index of fast forward of 240m/min and an acceleration of 5g (Amada laser cutting machine in Japan). Mazak company of Japan announced that it would launch a supersonic machining center with a fast moving speed of 500m/min, an acceleration of 6G, a spindle speed of 80000r/min and a cutting speed of Mach 8 in the near future. The transmission with high speed and high acceleration has been widely used in machining centers, CNC milling machines, lathes, grinders, compound machining machines, laser machining machines and heavy-duty machine tools. Such machine tools play a special role in the fields of aviation, automobile, mold, energy, general machinery and so on. The precision and stable movement of 0.1 (1) m can be realized by using linear motor drive on the electric machining machine tool. In micro machining and precision grinding, it can achieve 10um feed resolution, 20m/min fast moving speed and machining surface roughness

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