The common additive manufacturing techniques like fused filament fabrication (FFF) routinely produce physical, rigid structures. But using this production technique for manufacturing flexible structures with high-end materials such as thermoplastic polyurethane (TPU) is more difficult. Because of its difficulty, the fabrication of these structures requires higher-end machinery, time-intensive fabrication, and skilled users. Therefore, we focus on the malleable dynamics of a rigid thermoplastics with mid-range FFF technology to expand the design-space of shape-changing interfaces and propose a fabrication approach for it. As a result, the intended user, for example a creative designer, can also integrate shape-changing interfaces of rigid thermoplastics in their designs, much sooner than if constrained by an FFF printing platform. In a first phase, we experiment with different materials through an iterative design-based process. In a second phase, we perform an explorative design-case study to test the material’s flexibility and the fabrication approach. The research is concluded with an approach proposal, discussion and future work.