With the rapid development of electronic technology, the application of linear motor in the field of machine tool has reached its climax.From Chicago machine tool exhibition in 1996 IMTS ` 96, the 18th international machine tool exhibition in Japan, to the 1999 Paris international EMO fair and a series of international influential exhibition, this signal linear motor open up a new era has arrived.
In order to improve the production efficiency and improve the processing quality of the parts, the development of high speed and ultra-high speed processing has become a major trend of machine tool development.A responsive, high speed light drive system, speed will increase to more than 40 to 50 m/min, deceleration also calls for increased to 25 to 50 m/s2, the traditional "rotary motor and roller screw" form of transmission is obviously not enough, this is decided by its own weaknesses, first, because of the existence of intermediate transmission link stiffness is reduced, elastic deformation can make the system high order of time, and robustness of system is reduced, the servo performance degradation.The elastic deformation is the root of mechanical resonance of machine tool.Secondly, the middle drive link exists, which increases the inertia of the moving body, which causes the displacement and speed to slow down.In addition, factors such as the gap dead zone, friction, and error accumulation make this traditional way of maximum feeding speed of 30m/min and the acceleration of 3m/s2.
However, the advantages of direct motor drive can make up for the shortage of traditional transmission mode, and its speed is 30 times that of roller.The acceleration is 10 times that of the roller, the maximum can reach 10g, and the stiffness is increased by seven times.In addition, linear motor drives the workbench directly, so there is no reverse working dead zone;Due to the small inertia of the armature, the linear servo system composed of it can achieve a higher frequency response (eg, 100Hz).
The application of linear motor has a broad prospect in high speed and ultra-high speed precision machining.At present, it is mainly the communication linear motor that meets the requirements of the large thrust feed of machine tool, which can be divided into two types: permanent magnet (synchronous) type and induction (asynchronous) type.Permanent magnet subprime (stator) is the permanent magnets, applied in the machine tool, should be on machine tool bed laid permanent magnet steel, at the bottom of the table filled with three-phase power winding, form the primary (dynamic) linear motor.The induction type is the same as the permanent magnet type, but the second level is the use of the grid bar instead of the magnetic steel, which is equivalent to the "squirrel cage" of the induction rotating motor along its circumference.
The permanent magnet linear motor is superior to the induction type in terms of unit area thrust, power factor and controllability, but the price is more expensive, the installation and debugging, dust proof and other aspects are not equal to the induction type.
The induction linear motor has become more and more popular with the performance of the permanent magnet motor and its own advantages.
In the field of high speed and ultra-high speed machining, the linear motor is widely used in high speed milling machine, the crankshaft lathe, ultra precision lathe, grinding machine, laser machine thereof, the popular research now is it applied to high speed parallel mechanism, the structure of six axis, three axis parallel machine tool, he controls by flexing dogan sliding plunger cutter, realize the sticklebacks, the high speed machining.
