Described herein are systems and methods for securing a polymeric sheet to rib components of a frame structure, wherein the rib components are jointed at a hub to form an expandable and collapsible implant. In general, the method may include the steps of decreasing a diameter of the frame structure； placing the frame structure into an assembly fixture, wherein the assembly fixture is configured to hold the frame structure in a loaded configuration with a decreased diameter； placing a polymeric sheet into the assembly fixture； and heating the assembly under pressure to fuse the sheet to the frame structure. In general, a fixture may include a first and second platen having a shaping portion and a rim portion positioned around the periphery of the platen, wherein the shaping portions are configured to hold the rib components of the frame structure in a loaded configuration with a decreased diameter.
