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, which includes the electric spindle itself and its accessories: the electric spindle, high-frequency variable-frequency device, oil mist lubricator, cooling unit, built-in encoder, tool changer, etc.

The motor's rotor is directly used as the machine tool's spindle, with the spindle unit's housing serving as the motor base. When combined 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 technology (such as variable frequency speed regulation technology and motor vector control technology), the mechanical structure of high-speed CNC machine tool main drive systems has been greatly simplified. Belt and gear drives have basically been eliminated. The machine tool spindle is directly driven by an internally mounted motor, thereby reducing the length of the machine tool main drive chain to zero, achieving the "zero transmission" of the machine tool.

This type of 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 drive system and overall structure. Consequently, it can be formed into a "spindle unit," commonly known as an "electric spindle." As the electric spindle predominantly 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."