A mold assembly has an upper positioning seat, an upper panel disposed in the upper positioning seat, a lower positioning seat, a lower panel disposed in the lower positioning seat, a first air cylinder disposed on a side of the lower positioning seat, a second air cylinder disposed on a bottom of the lower positioning seat, a third air cylinder disposed on a side of the upper positioning seat, and a fourth air cylinder disposed on a top portion of the upper positioning seat. A lower plate is disposed on a bottom of the upper panel. An upper plate is disposed on the lower panel. The lower plate engages with the upper plate.