Three-axis linkage inverted vertical lathe and method for machining curved surface of inner hole of part through three-axis linkage inverted vertical lathe

According to the structure of the three-axis linkage inverted vertical lathe, the whole lathe body is of a U-shaped structure, and an open groove of the U-shaped structure is formed in the front-back direction of the lathe body; the top face of the lathe bed is connected with a beam through a transmission mechanism, the front surface of the beam is connected with a spindle box through a transmission mechanism, and a spindle in the spindle box extends into an open groove of a U-shaped structure. A U-shaped cradle body swing device is arranged at the front end of an inner cavity of the open groove, the middle of the cradle body swing device is connected with a self-driven milling cutter, and a rotating B shaft is formed between the cradle body swing device and the lathe bed. A Y-axis conveying mechanism is arranged at the rear end of the cradle body swinging device, the Y-axis conveying mechanism penetrates through the bed body along the Y axis, a tray tool is arranged on the Y-axis conveying mechanism, and a w