How to Control the Surface Flatness of Double-Curved GRC Panels? A Full-Process Precision Control Solution

Double-curved GRC panels, due to their bidirectional curved surfaces, are difficult to control for surface flatness; if the precision falls short, it affects the overall decorative effect and joint sealing. Drawing on its practice in the Shanghai Qingpu R&D and production project, Qinglong analyzes the core technologies and full-process solutions for controlling the surface flatness of double-curved GRC panels.

I. Mold Precision as the Fundamental Guarantee of Flatness

High-precision molds are the prerequisite for flatness control. Mold material and machining: GRP or polyurethane molds are selected, with surface roughness ≤0.8μm, machined using CNC engraving machines; the precision error of double-curved surfaces is ≤±0.5mm, and Qinglong's digital mold machining precision can reach ±0.1mm. Mold joining and reinforcement: multi-piece joined molds must ensure flat and even joint seams with error ≤0.2mm; reinforcing ribs are added to the back of the molds to prevent deformation during casting, with rib spacing ≤800mm. Mold cleaning and release agent: before casting, thoroughly clean impurities from the mold surface and evenly apply a dedicated release agent to prevent slurry adhesion that causes surface defects; the release agent coating thickness is ≤0.1mm.

II. Precise Flatness Control During Production

Refined production operations reduce surface deviations. Slurry mix optimization: a low-shrinkage GRC slurry formula is adopted with 10%-15% silica fume added to improve slurry flowability and compactness, preventing uneven shrinkage after hardening that would cause surface undulations. Spray molding process: high-pressure spray molding technology is used, with spray pressure controlled at 0.3-0.5MPa and a uniform nozzle movement speed (≤0.5m/s); the layered spraying thickness is 3-5mm to ensure a flat surface. Vibration and compaction: after spraying, the mold is lightly vibrated with a high-frequency vibrator (frequency 2000-3000 times/minute) to remove internal air bubbles, then compacted with a dedicated curved-surface scraper so that the surface perfectly conforms to the mold.

III. Flatness Optimization Through Curing and Post-Processing

Scientific curing and treatment ensure stable surface quality. Standardized curing process: constant temperature and humidity curing is adopted (temperature 20-25°C, humidity ≥90%) with a curing period ≥14 days to prevent surface cracking or deformation caused by improper early curing. Surface grinding treatment: after demolding, locally uneven areas are ground using 800-1200 grit sandpaper with a grinding depth ≤0.5mm to ensure smooth surface transitions. Flatness inspection: a 2m straightedge and a laser flatness gauge are used for testing, with ≥3 inspection points per square meter on double-curved surfaces and flatness error ≤±1mm. Before leaving the factory, Qinglong conducts flatness spot checks on every component, with a required pass rate of 100%.

IV. Flatness Joint Control During Installation

Precise installation ensures the flatness of the overall curved surface. Installation reference setup: BIM technology is used to establish a 3D installation reference, and component positions are calibrated with laser positioning instruments, with installation error ≤±0.5mm. Joint seam treatment: the joint seam width of double-curved GRC panels is controlled at 8-12mm and filled with high-elasticity sealant flush with the component surface to prevent visual flatness deviations caused by gaps. Overall inspection and adjustment: after all components are installed, an overall laser scanning inspection is performed, and areas exceeding flatness tolerances are fine-tuned to ensure the overall curved surface is smooth and uniform. Qinglong applied this method in the Guangxi New Media Center project, achieving an overall flatness error ≤±2mm.