Main drive
For the main drive, the most important is the use of closed-loop control synchronous motor and asynchronous motor. They are used as combined motors and enclosed motors in lathes, milling machines, grinding machines, and machining centers.
The traditional use of enclosed-motor-driven spindle drives, largely air-cooled, is very common. Compared to motor spindles, it is considered an economical solution, taking into account the secondary costs of both systems. The intermediate shifting of the gearbox makes it possible, on the one hand, to match the speed and torque to the machining requirements, and on the other hand, the gearbox generates undesired radial forces, noise and increased wear.
The spindle drive concept using a combined motor with spindle integration is fully mature on a technical level. Since the gearbox and clutch can be eliminated, in this drive a completely centered swivel motion without radial forces can be achieved, which is marked by long-term smooth motion and minimal wear and is especially suitable for high-power cutting operations.
Generating high torque is still complicated, either a (planetary) transmission must be integrated on the main shaft, or a high-power motor must be selected. For preventive maintenance and repairs, monitoring sensors integrated on the shaft have now been developed as standard for measurement data acquisition, while cooling with oil, air or glycol is essential!
Feed drive
Feed drive can be realized by mechatronics or hydraulic system. Choose according to the advantages and disadvantages of different specific drive technologies.
At present, most of the mechatronic feed drives in the world use servo motors with ball screw drive systems to convert rotary motion into linear motion. Unlike main drives, here, synchronous enclosed motors are preferred from the standpoint of high demands on positioning accuracy, synchronization and dynamic performance.
Due to its high static stiffness, this drive system can be used in many fields and has become a traditional solution. However, the wear is very large. Depending on the installation situation and the magnitude of the torque to be generated, the servo motor directly or through a tooth profile The belt is connected to the spindle.
Although the principle of electric linear motors was invented in the 19th century, this technology did not begin to be applied to machine tools until the 1990s. At that time Rexroth equipped the first series of machine tools with linear motors. The combination of wear-free, high strength and high dynamics of this drive is generally welcomed. It thus guarantees long-term trouble-free operation with high precision compared to comparable ball screw drives with indirect displacement measuring systems.
On the one hand, the limitation of use lies in the carrying capacity of the drive: therefore, for occasions with high cutting forces, it is still impossible to abandon the use of ball screw drive systems or hydraulic drive solutions. On the other hand, in relation to other involved machine components, for example, the maximum permissible moving speed of the cutting shield and the damping performance of the guide slide also limit the use of the drive. The advantages of linear motor drive technology compared with the associated investment costs have also hindered the worldwide breakthrough of this drive technology so far.
This type of drive is only used when the advantages of hydraulic feed drive are considered. Mainly used in small installation space, high dynamic characteristics or large feed driving force occasions. It goes without saying that for hydraulic feed drives, precise positioning on the micron scale must be possible.
The specific practical application has always required that the hydraulic linear drive must be able to work for a long time without backlash and have a longer service life than the ball screw drive system. For electric feed drives, the corresponding power (torque and speed) must be installed, while the hydraulic drive shaft receives energy on demand in a pressurized liquid accumulator, so the installed power can be reduced by 80%.