Electrical spindle is in the field of CNC machine tools will appear in the machine tool spindle and spindle motor into one of the new skills, electrical spindle it with linear motor skills, high-speed tooling skills together, high-speed machining for a new era. The electric spindle includes the electric spindle itself and its accessories, including the electric spindle, high-frequency frequency conversion equipment, oil mist smoother, cooling equipment, built-in encoder, tool changer equipment, and so on. The rotor of the electric motor is directly used as the spindle of the machine tool, and the shell of the spindle unit is the motor base, and it cooperates with other parts to complete the integration of the electric motor and the spindle of the machine tool.
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With the agile development of electrical transmission technology (frequency control technology, motor vector control technology, etc.) and increasingly perfect, high-speed CNC machine tools, the mechanical structure of the main drive system has been greatly simplified, basically eliminating the belt wheel drive and gear transmission. The machine tool spindle is directly driven by the built-in motor, thus shortening the length of the main transmission chain to zero, completing the machine tool "zero transmission". This "spindle unit" spindle motor and machine tool spindle "into one" transmission structure method so that the spindle components from the machine tool transmission system and the overall structure of the relatively independent, also known as "electric spindle" (ElectricSpindle, Motor Spindle). As the primary choice of electric spindle is AC high-frequency motor, it is also known as "high frequency spindle" (High FrequencySpindle). Because there is no intermediate transmission link, sometimes also called "direct drive spindle" (Direct Drive Spindle).
Electrical spindle structure
The spindle consists of a motor without shell, spindle, bearings, spindle unit shell, drive module and cooling equipment. The rotor of the motor is integrated with the spindle in a press-fit method, and the spindle is supported by front and rear bearings. The stator of the motor is placed in the housing of the spindle unit through a cooling jacket. The spindle speed is controlled by the spindle drive module and the temperature rise in the spindle unit is limited by the cooling equipment. The spindle is equipped with speed and angular displacement sensors at the rear end of the spindle, and the front end has an internal taper hole and end face for tooling.
Cooling of the motorized spindle
Due to the spindle will be integrated in the spindle unit, and the speed is very high, the operation will generate a lot of heat, caused by the temperature rise of the spindle, so that the thermal characteristics of the spindle and the dynamic characteristics of the spindle deterioration, thus affecting the normal operation of the spindle. Therefore, it is necessary to adopt certain methods to control the temperature of the spindle, so that it is constant within a certain value. Machine tools are generally adopted by the forced circulation of oil cooling method of the stator of the spindle and spindle bearing cooling, that is, through the oil cooling equipment cooling oil mandatory in the spindle outside the stator and the spindle bearing outside the cycle, to take away the heat generated by high-speed rotation of the spindle. In addition, in order to reduce the heat of the spindle bearings, it is also necessary to carry out reasonable smoothing of the spindle bearings.
Electric spindle drive
Electric spindle motor are selected AC asynchronous induction motor, so used in high-speed machining machine tools, start from a standstill agile speed to tens of thousands of revolutions per minute or even hundreds of thousands of revolutions per minute, start torque is large, so the start-up current to exceed the rated current of ordinary motors 5 to 7 times. The drive method has inverter drive and vector control drive drive two kinds. Frequency converter drive control characteristics for constant torque drive, the output power and torque is proportional. The latest machine tool frequency converter using advanced transistor technology, can be completed stepless speed change of the spindle. Machine tool vector control drive drive control for the low-speed end of the constant torque drive, in the middle and high-speed end of the constant power drive.
European electric spindle manufacturers
The world's leading electric spindle companies are mainly concentrated in Europe and Japan, in which the leading European manufacturers of electric spindles with strong R & D strength, excellent product performance, a long history of production and good performance reputation, in the different applications of electric spindles are occupying an important market share, representing the world's highest level in their respective fields. Among them, the more famous ones are
SycoTec (former kavo) from Germany,
FISCHER from Switzerland and IBAG from Switzerland. Japan's spindle technology level is relatively behind Europe, but the industry is mature, cost-effective, in mainland China and other spindle technology is relatively backward region occupies a large market share.
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