How to Control the Surface Flatness of Double-Curved GRC Panels? Full-Process Precision Management from Mould to Installation

Surface flatness control of double-curved GRC panels is a systematic engineering effort spanning the entire process of design, mold making, production and curing, transportation, and installation—loss of control at any stage will degrade the final visual effect and installation quality. Qinglong Group has set its internal control standard for the flatness of double-curved GRC panels as: checked with a 2-meter straightedge, panel surface flatness deviation ≤2mm, and height difference between adjacent panel surfaces at joints ≤1.5mm. Achieving this high standard requires establishing a comprehensive precision assurance system.

Control begins with high-precision digital molds. Double-curved molds must be directly milled to shape using five-axis CNC equipment on tooling board (wood substitute) or high-strength resin substrates, with the machining accuracy of the mold surface controlled within ±0.2mm. The mold itself must possess sufficient rigidity and stability to remain undeformed through repeated use and production vibration. During production, the spraying or casting of the GRC mix must be uniform to avoid internal stresses caused by uneven material buildup that would lead to later warping. Curing is the key to controlling shrinkage deformation: a standardized steam curing regime must be adopted with the rates of temperature rise and fall controlled, and sufficient wet curing must continue after demolding to stabilize dimensions. In the Shenzhen Yirui Biotechnology Building project, we raised the production flatness pass rate of double-curved panels to over 99% through constant temperature and humidity curing rooms.

Protection during transportation and storage is equally important. Double-curved panels must be transported vertically on custom supports or laid flat on absolutely level racks to prevent bending caused by their own weight or external forces. Installation is the final critical step in achieving the ultimate flatness. First, the flatness of the supporting framework (steel frame or concrete substrate) must be adjusted to meet the standard beforehand (usually required to be ≤3mm/2m). Second, the connection joints must adopt a three-dimensionally adjustable system, allowing fine adjustment up and down, left and right, and front and back. During installation, following the principle of "from the whole to the parts," a datum plane is first established with measuring instruments and locating panels installed, then the remaining panels are installed in sequence, with continuous verification using straightedges and laser scanners. In the installation of nearly 10,000 double-curved panels for the Wuhan Han Show Theatre, we achieved an extremely smooth curved surface effect for the entire curtain wall through full-process digital surveying assistance during construction.