An annular thermoplastic foam extrusion die assembly has a first die body with a first die lip and a second die body with a second die lip. The first die body includes a trench having an undercut, sloped back wall and a circumferential groove opposite the back wall. A plurality of die lip paddles are spaced apart about an annular groove, each with a tip and a heel. The tip is received for pivotal movement in the groove. The heel engages with the back wall as the heel is raised to drive the first die lip toward the second die lip to adjust a local position of the annular die gap formed therebetween. The lifting mechanism raises and lowers each of the paddles individually. The guide member guides each of the die lip paddles for positioning in a radial direction as the paddle is pivotally positioned about the annular groove.