How to Control the Surface Flatness of Double-Curved GRC Panels? Millimeter-Level Curved Surfaces and Qinglong Group's Precision Control System

Surface flatness control of double-curved GRC panels is a core indicator of manufacturing and installation quality, directly affecting the light-and-shadow effects and visual quality of building façades. Its control spans three key stages: "mold precision, production deformation, and installation leveling." Qinglong Group sets its internal flatness standard for double-curved panels at: deviations ≤2mm in any direction under a 2-meter straightedge, and joint misalignment between adjacent panels ≤1mm. In the red double-curved curtain wall project of the Wuhan Han Show Theatre, through five-axis CNC high-precision molds (surface error ≤±0.5mm), a constant temperature and humidity curing regime, and a three-dimensionally adjustable connection system, we kept the overall installation flatness of 287 unique double-curved panels within 1.5mm/2m, achieving a silky-smooth curved surface. Flatness is the "face" of curved GRC and demands meticulous craftsmanship at every stage.

High-Precision Molds Are the Innate DNA of Flatness

The flatness of double-curved panels is determined first by mold surface precision. We use five-axis CNC machining centers to produce steel or resin molds, ensuring the mold's own surface error is controlled within ±0.5mm. Molds must have sufficient rigidity to prevent deformation under repeated use and production vibration. Draft angles must be precisely calculated (typically 1-3°) to ensure smooth demolding without compromising the design curvature.

The Production Process Is Key to Controlling Deformation

Every stage of the GRC slurry process—mix proportion, mixing, spraying/casting, and curing—affects the flatness of the formed panel. We use low-shrinkage mix proportions (with expansion agents or fibers), robotic uniform spraying, and vacuum dewatering to reduce internal defects and uneven shrinkage. A standardized curing regime (temperature fluctuation ≤±2℃) is strictly enforced to prevent warping caused by sudden changes in temperature and humidity. After demolding, panels must rest horizontally on dedicated alignment frames for at least 7 days to release residual stresses.

The Installation Leveling System Is the Ultimate Guarantee of Precision

Even if the panels themselves are flat, improper installation can undo all previous efforts. We use a three-dimensionally adjustable metal bracket system that allows fine adjustment of more than ±10mm in the X, Y, and Z directions. During installation, laser levels and straightedges are used to adjust panel by panel, ensuring smooth transitions across the overall curved surface. On the roof of the Hainan Convention and Exhibition Center, a closed-loop process of "measure-adjust-fix-verify" achieved a mirror-like visual effect over large surfaces.

Digital Inspection Enables Full-Process Monitoring

Using 3D laser scanning technology, panels before shipment and façades after installation are scanned to generate point cloud models that are compared with design models, visually displaying flatness deviations. This digital acceptance method allows us to precisely locate problems and continuously improve our processes. Qinglong Group guarantees a flatness pass rate of up to 99% for double-curved panels.

Controlling the flatness of double-curved GRC panels is a protracted battle that begins at the "millimeter" level. Through refined, full-process control, Qinglong Group enables even complex curved surfaces to achieve the ultimate in flatness and smoothness.