The grinding electric spindle is a new technology that integrates the spindle and motor in machine tools, emerging in the CNC machine tool field. Along with 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 system, built-in encoder, tool changing unit, etc.

The motor's rotor is directly used as the machine tool's spindle, with the housing of the spindle unit 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 refinement of electrical transmission technologies (such as variable frequency speed regulation and motor vector control), the mechanical structure of high-speed CNC machine tool main drive systems has been greatly 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 drive chain to zero, achieving the "zero transmission" of the machine tool.

This drive structure integrates the spindle motor with the machine tool's spindle, making the spindle component relatively independent from the machine's transmission system and overall structure. As a result, it can be formed into a "spindle unit," commonly known as an "electrical spindle." Since the electrical 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, it is sometimes called a "direct drive spindle."