What Are The Characteristics Of The Spindle Of Cnc Machining Center

[Grayce Bird]

Motorized spindle is a new technology in the field of NC machine tools, which integrates the machine tool spindle and spindle motor. Together with linear motor technology and high-speed tool technology, it promotes high-speed machining to a new era. Motorized spindle is a set of components, which includes motorized spindle itself and its accessories: motorized spindle, high-frequency frequency conversion device, oil mist lubricator, cooling device, built-in encoder, tool change device, etc. The rotor of the motor milling operation is directly used as the spindle of the machine tool, and the shell of the spindle unit is the motor base, which cooperates with other parts to realize the integration of the motor and the spindle of the machine tool
motorized spindle is composed of motor without housing, spindle, bearing, spindle unit housing, drive module and cooling device. The rotor of the motor is integrated with the main shaft by press fitting method, and the main shaft is supported by front and rear bearings. The stator of the motor is installed in the shell of the spindle unit through the cooling sleeve. The speed change of the spindle is controlled by the spindle drive module, and the temperature rise in the spindle unit is limited by the cooling device. The rear end of the main shaft is equipped with speed and angle displacement sensors, and the inner conical hole and end face at the front end are used to install tools
because the motorized spindle integrates the motor into the spindle unit and the speed is very high, a large amount of heat will be generated during operation, which will cause the temperature rise of the motorized spindle and deteriorate the thermal and dynamic characteristics of the motorized spindle, thus affecting the normal operation of the motorized spindle. Therefore, certain measures must be taken to control the temperature of the motorized spindle to keep it constant within a certain value. At present, the machine tool generally adopts the method of forced circulating oil cooling to cool the stator and spindle bearing of the motorized spindle, that is, the cooling oil passing through the oil cooling device is forcibly circulated outside the spindle stator and spindle bearing to take away the heat generated by the high-speed rotation of the spindle. In addition, in order to reduce the heating of the spindle bearing, the spindle bearing must be lubricated reasonably
the motors of motorized spindle are all AC asynchronous induction motors. As they are used on high-speed machining machine tools, the speed should be rapidly increased from static to tens of thousands or even hundreds of thousands of revolutions per minute when starting. The starting torque is large, so the starting current should exceed the rated current of ordinary motors by 5 ~ 7 times. There are two driving modes: frequency converter drive and vector control drive. The drive control characteristic of the frequency converter is constant torque drive, and the output power is directly proportional to the torque. The latest frequency converter of the machine tool adopts advanced transistor technology, which can realize the stepless speed change of the spindle. The drive control of machine tool vector control driver is constant torque drive at low speed end and constant power drive at medium and high speed end

according to the spindle transmission mode, it can be divided into three categories: belt type, direct connected type and motorized spindle

belt spindle

advantages: it has great strength and is suitable for heavy cutting. It is widely used in large machine tools

disadvantages: positioning deviation, troublesome debugging and relatively large noise

Direct spindle

advantages: stable processing, and the plane finish is higher than that of belt drive

disadvantages: the strength of heavy cutting is not as strong as that of belt drive

motorized spindle

advantages: high-speed processing, mainly milling, with the highest finish

disadvantages: because the speed is too fast and the cutting force is insufficient, it is only for milling and has little function.

common speed values of major spindles:

belt spindle: 3000-6000-8000-10000-12000rpm

Direct spindle: 10000-12000rpm

motorized spindle: 24000-30000-50000rpm (hundreds of thousands of speeds abroad)