The grinding electric spindle is a new technology that integrates the machine tool spindle with the spindle motor in the CNC machine tool field. Alongside linear motor technology and high-speed tooling technology, it propels high-speed machining into a new era. The electric spindle is a set of components, including the electric spindle itself and its accessories: the electric spindle, high-frequency variable frequency device, oil mist lubricator, cooling unit, built-in encoder, tool changing device, etc.

The motor's rotor serves directly as the machine tool's spindle, with the spindle unit's housing being the motor base. Along with other components, this achieves an integrated design between the motor and the machine tool's spindle.

Currently, with the rapid development and maturation of electrical transmission technologies such as variable-frequency speed control and motor vector control, the mechanical structure of high-speed CNC machine tool main transmission systems has been significantly simplified, essentially eliminating belt and gear drives. The machine tool spindle is directly driven by an integral motor, thereby reducing the length of the machine tool's main transmission chain to zero, achieving "zero transmission" in machine tools.

This drive structure, where the spindle motor is integrated with the machine tool spindle, allows the spindle component to be relatively independent from the machine's transmission system and overall structure. Consequently, it can be made into a "spindle unit," commonly known as an "electric spindle." As the electric spindle primarily uses AC high-frequency motors at present, it is also referred to as a "high-frequency spindle." Due to the absence of intermediate transmission stages, it is sometimes called a "direct drive spindle."