Automatic undercut forming device for square cavity

The utility model relates to an automatic square cavity undercut forming device which comprises a feeding pre-assembling machine, a cavity base used for containing a U-shaped cavity is installed on the top face of the feeding pre-assembling machine, end cover bases used for containing end covers are installed outside the two ends of the cavity base respectively, and the U-shaped cavity and the end covers at the two ends are pre-assembled into pre-assembling structures which are spaced front and back through the feeding pre-assembling machine. The device further comprises an undercut machine, the preassembling structure is transferred into the undercut machine through the feeding clamping jaw, the undercut machine enables the end covers to oppositely get close to the two ends of the U-shaped cavity through the pushing mechanism, and the undercut driving mechanism moves along the edges of the ends of the U-shaped cavity to achieve undercut, so that undercut forming of the square cavity is achieved in an automat