What is the acceptable curvature tolerance for GRC shapes?

Curvature error in GRC profiles is a core parameter for measuring shape fidelity and manufacturing workmanship. For regular circular arcs, elliptical arcs, and free-form hyperbolic surfaces in particular, strict curvature control is the foundation of achieving the desired architectural aesthetic effect. Based on Qinglong Group's 28 years of project experience and internal quality control standards, the curvature error of GRC components must be controlled in tiers according to their size, radius of curvature, and visual position. Typically, the curvature error of a single component is kept within 1/500 of its chord length, or the maximum local deviation does not exceed ±3mm, to ensure visual continuity and smoothness after overall installation.

For gentle curves with a large radius of curvature (R>5m), since the human eye is not sensitive to slight irregularities, the curvature error can be relaxed appropriately, but the deviation of the overall contour line from the theoretical curve should still not exceed ±10mm. For sharp bends or rolled edges with a small radius of curvature (R<1m), since any tiny deviation will be magnified under light and shadow, the control requirements are extremely strict—typically the curvature error must not exceed ±2mm. When producing such components, Qinglong fabricates dedicated inspection templates for 100% inspection, ensuring that every component matches the design model.

Control of curvature error runs through the entire process. First, at the digital modeling stage, the model used to guide production must itself be smooth, to avoid production errors caused by model quality issues. Second, at the mold-making stage, machining with high-precision five-axis CNC machines is the prerequisite for ensuring the accuracy of the mold's own curvature. Qinglong's mold curvature error is typically controlled within ±1mm. Finally, at the production and curing stage, factors such as the shrinkage of GRC slurry during setting and the elastic springback after demolding will all affect the final curvature, requiring pre-compensation based on empirical data. By establishing a springback database for components with different mix formulations and thicknesses, Qinglong performs reverse correction at the mold design stage, effectively offsetting production deformation and ensuring that the finished curvature meets design requirements.