How Do UHPC Single-Curved and Double-Curved Panels Differ in Mold Requirements? A Technical Leap from 2D Bending to 3D Shaping

The mold requirements for UHPC single-curved panels (curved in only one direction) versus double-curved panels (curved in two directions) are essentially the difference between manufacturing two-dimensional surfaces and three-dimensional freeform surfaces, with complexity, precision requirements, and cost increasing exponentially. When handling these two types of components, Qinglong Group adopts entirely different strategies, from design thinking to processing techniques.

For single-curved panels, the curved surface can be generated by translating a generatrix along a directrix, such as a cylindrical or conical surface. Molds for such components are relatively simple to fabricate and low in cost. Typically, an approach of "bent or rolled substrate + surface mold overlay" can be adopted. For example, to create a mold with a single-direction cylindrical curve, we first use a large plate rolling machine to roll a steel plate to the designed radius of curvature, then finish-machine its surface and spray a highly polished polymer coating. Such molds can efficiently produce panels with consistent arc profiles and offer high reusability. Precision control mainly focuses on the straightness along the generatrix direction and the accuracy of the radius of curvature.

For double-curved panels, however, the curvature at every point of the surface may differ (such as spherical surfaces, saddle surfaces, or more complex freeform surfaces), so the mold must be a fully three-dimensional negative or positive mold. This requires the mold itself to be a high-precision three-dimensional solid. We typically machine it directly from a solid block of high-density tooling board, engineering plastic, or aluminum alloy using a large five-axis CNC machine. Every surface point on the mold must match the digital model exactly, as even the slightest deviation may prevent adjacent panels from joining properly. For example, when our company produced double-curved petal-shaped curtain walls for an opera house in Guangzhou, the mold for every panel was unique, and rigorous virtual pre-assembly checks had to be performed before fabrication to ensure the continuity of the spatial surfaces. The supporting steel structure of the mold also requires special design to resist the enormous lateral pressure generated during UHPC casting and vibration, preventing mold deformation.

In addition, demolding difficulty also differs significantly. Single-curved panels usually require only unidirectional demolding, whereas double-curved panels—especially those with "negative angles" (i.e., concave shapes)—may need to be designed as detachable composite molds, which further increases mold complexity and cost. Therefore, in the early stages of a project, Qinglong Group's technical team works closely with architects, using Gaussian curvature analysis of curved surfaces to rationalize and optimize complex double-curved surfaces into developable single-curved or nearly single-curved surfaces wherever possible, substantially reducing mold costs and fabrication difficulty while preserving the design effect.