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 inverter, oil mist lubricator, cooling system, built-in encoder, tool changing device, etc.

The motor rotor is directly used as the machine tool's spindle, with the spindle unit's housing serving as the motor base. Together with other components, it achieves an integrated design between the motor and the machine tool's spindle.

Currently, with the rapid development and improvement of electrical transmission technology (such as variable frequency speed regulation technology and motor vector control technology), the mechanical structure of the main transmission system of high-speed CNC machine tools has been greatly simplified, and belt drives and gear drives have basically been eliminated. The machine tool spindle is directly driven by an integral motor, thus shortening the length of the machine tool's main transmission chain to zero, achieving the "zero transmission" of the machine tool.

This drive structure, where the spindle motor and the machine tool's spindle are integrated as one, allows the spindle component to become relatively independent from the machine's transmission system and overall structure. Consequently, it can be constructed into a "spindle unit," commonly known as an "electric spindle." Since the electric spindle predominantly uses AC high-frequency motors currently, 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."