The grinding electrical 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 tool technology, it propels high-speed machining into a new era. The electrical spindle is a set of components, including the electrical spindle itself and its accessories: the electrical spindle, high-frequency variable frequency device, oil mist lubricator, cooling unit, built-in encoder, tool changer, etc. The motor's rotor serves directly as the machine tool's spindle, with the spindle unit's housing being the motor base. In conjunction with other components, this achieves integration between the motor and the machine tool spindle.

Currently, with the rapid development and improvement of electrical transmission technology (such as variable frequency speed regulation technology, motor vector control technology, etc.), the mechanical structure of the high-speed CNC machine tool main transmission system has been greatly simplified, and belt drives and gear drives have basically been eliminated. The machine tool spindle is directly driven by an internal motor, thereby shortening the length of the machine tool main transmission chain to zero, achieving "zero transmission" in machine tools. This transmission structure, where the spindle motor is integrated with the machine tool spindle, makes the spindle component relatively independent from the machine tool's transmission system and overall structure, thus allowing it to be made into a "spindle unit," commonly known as an "electric spindle." As the current electric spindle mainly uses AC high-frequency motors, it is also called a "high-frequency spindle." Due to the absence of intermediate transmission stages, it is sometimes referred to as a "direct drive spindle."