The grinding electric spindle is a new technology that integrates the machine tool spindle with the motor 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, which includes the electric spindle itself and its accessories: the electric spindle, high-frequency inverter, oil mist lubricator, cooling device, built-in encoder, tool changing device, etc.

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

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

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 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."