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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 ar

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.

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The invention claimed is: 1. An annular thermoplastic foam extrusion die assembly, comprising: an annular die having a first die body with a first die lip and a second die body with a second die lip, the second die body positioned adjacent the first die body with the second die lip configured relat

The invention claimed is: 1. An annular thermoplastic foam extrusion die assembly, comprising: an annular die having a first die body with a first die lip and a second die body with a second die lip, the second die body positioned adjacent the first die body with the second die lip configured relative to the first die lip to form an annular die gap therebetween, the first die body including a trench having an undercut, sloped back wall and the first die lip having a circumferential groove opposite the back wall; a plurality of die lip paddles spaced apart about the annular die gap, each having a tip and a heel, the tip configured to be received for pivotal movement in the groove and the heel configured to engage with the back wall as the heel is raised to drive the first die lip toward the second die lip to adjust a local portion of the annular die gap formed therebetween; a lifting mechanism configured to independently raise and lower each of the paddles; and a guide member configured to guide each of the die lip paddles for positioning in a radial direction as each of the paddles is independently pivotally positioned about the annular groove. 2. The annular thermoplastic foam extrusion die assembly of claim 1 wherein the first die lip of the first die body comprises an outer die lip. 3. The annular thermoplastic foam extrusion die assembly of claim 2 wherein the outer die lip comprises a cylindrical outer die lip. 4. The annular thermoplastic foam extrusion die assembly of claim 1 wherein the second die lip of the second die body comprises an inner die lip. 5. The annular thermoplastic foam extrusion die assembly of claim 4 wherein the inner die lip comprises a cylindrical die lip. 6. The annular thermoplastic foam extrusion die assembly of claim 1 wherein the die lip paddle further comprises a tapering finger extending from the tip towards the heel. 7. The annular thermoplastic foam extrusion die assembly of claim 6 wherein the die lip paddle comprises a sloped back wall extending upwardly from the heel and configured to mate in complementary relation with the undercut, sloped back wall on the trench of the first die body. 8. The annular thermoplastic foam extrusion die assembly of claim 1 wherein the lifting mechanism comprises an adjuster support ring extending circumferentially about the first die body and configured to support the plurality of die lip paddles in circumferentially spaced-apart relation about the first die body. 9. The annular thermoplastic foam extrusion die assembly of claim 8 wherein the adjuster support ring comprises a plurality of arcuate ring members having individual slots configured to support a respective one of the die lip paddles for positioning inwardly and outwardly along the radial direction. 10. The annular thermoplastic foam extrusion die assembly of claim 9 further comprising bores provided in the ring members of the adjuster support ring about each slot and a threaded bolt configured to extend through the bore and into a tapped hole in a respective one of the die lip paddles configured to raise and lower the paddle relative to the collar responsive to threading engagement therebetween. 11. The annular thermoplastic foam extrusion die assembly of claim 8 wherein the guide member comprises a slot provided in the adjuster support ring formed in a radial direction and configured to guide a respective one of the die lip paddles in a radial raised and lowered direction as the paddle is pivotally positioned about the annular die gap. 12. A thermoplastic foam extrusion die assembly, comprising: an annular die having a die body, a first die lip, and a second die lip, the second die lip spaced from the first die lip to provide an annular die gap there between, the die body including an undercut, sloped back wall and the first die lip having a circumferential groove opposing the back wall; a plurality of die lip wedges, each wedge having a tip and a heel, the tip configured to be received for pivotal movement in the groove of the first die lip and the heel configured to engage with the back wall of the die body; a collar encompassing the die body and having a plurality of guide slots spaced circumferentially about the die body each supporting one of the wedges; and a lifting mechanism for independently raising and lowering individual ones of the wedges as the heel of a selected wedge is raised into engagement with the back wall to drive the first die lip toward the second die lip to adjust a local portion of the annular die gap formed therebetween. 13. The thermoplastic foam extrusion die assembly of claim 12 wherein the second die lip is supported by the die body for movement relative to the first die lip. 14. The thermoplastic foam extrusion die assembly of claim 12 wherein the wedge further comprises a tapering finger extending from the tip towards the heel. 15. The thermoplastic foam extrusion die assembly of claim 12 wherein the wedge comprises a sloped back wall extending upwardly from the heel and configured to mate in complementary relation with the undercut, sloped back wall on the die body. 16. The thermoplastic foam extrusion die assembly of claim 12 wherein the collar comprises a cylindrical collar having a plurality of arcuate collar members each having a plurality of arches, with each arch providing one of the guide slots. 17. The thermoplastic foam extrusion die assembly of claim 16 wherein the lifting mechanism comprises a threaded bolt configured to be received through a bore in one of the arches of the collar and configured to mate in threaded engagement with a threaded bore in one of the wedges. 18. An extrusion die for polymeric material, comprising: a die having a die body, an outer die lip, and an inner die lip cooperating with the outer die lip to define an annular die gap, the die body including an undercut, sloped back wall and the outer die lip having a circumferential groove opposing the back wall; a plurality of die lip wedges, each wedge having a tip and a heel, the tip configured to be received for pivotal movement in the groove of the first die lip and the heel configured to engage with the back wall of the die body; a frame provided about the die body and having a plurality of slots spaced circumferentially about the die body to guide each of the wedges; and a lifting mechanism for independently raising and lowering individual ones of the wedges, the heel of each selected wedge being raised into engagement with the back wall to drive the first die lip toward the second die lip to adjust an adjacent portion of the annular die gap. 19. The extrusion die of claim 18, wherein the frame comprises a collar, and the slots comprise guide slots each extending in a radial direction within the collar. 20. The extrusion die of claim 18, wherein the lifting mechanism comprises a plurality of arcuate ring members extending circumferentially about the die body including a plurality of bores spaced circumferentially about the die body and a plurality of threaded bolts each configured to extend through a respective bore and into a complementary tapped hole in a respective wedge and adjustable to raise and lower the wedge relative to the respective ring member.