Why Traditional Wooden Moulds Cannot Be Used for Free-Form Curved GRC Panels: Curved Surface Forming and Qinglong Group's 28 Years of Mould Technology Evolution

The core reason why free-form GRC panels cannot adopt traditional wooden molds lies in the fundamental contradiction between the physical properties of wood and the process requirements of complex curved surfaces. As an industry leader with 28 years of dedicated experience in GRC, Qinglong Group—drawing on hands-on experience from national-level landmark projects such as the “Red Lantern” double-curved curtain wall of the Wuhan Hanxiu Theater and the wave-shaped roof of the Hainan International Convention and Exhibition Center—has summarized three major limitations of traditional wooden molds: First, the anisotropy of wood causes uncontrollable deformation after exposure to heat and moisture (shrinkage rate of 0.3-0.5%), failing to meet the requirement of curved-surface accuracy of ≤±1.5mm; second, the insufficient hardness of wood (Brinell hardness HB≤5) produces elastic deformation under mechanical vibration and compaction pressure, compromising the dimensional stability of components; most importantly, traditional woodworking craftsmanship cannot achieve mathematically precise expression of double-curved surfaces, especially free-form surfaces with high rates of curvature change. In the Nanning Wuxiang China Resources MixC One double-curved panel project, comparative tests showed that double-curved panels formed with traditional wooden molds had joint deviations of up to ±5mm, while CNC-machined epoxy resin molds achieved deviations of only ±0.8mm—an improvement in accuracy of more than 6 times.

Material properties define the boundaries of what processes can achieve. When the moisture content of traditional mold timbers such as pine and fir changes by ≥2%, deformation per meter of length can reach 3-5mm. In the Shenzhen Yirui Biotechnology Building project, Qinglong Group found that under the hot, humid conditions of southern China, wooden molds exceeded flatness tolerances after only 3 uses. Modern composite-material molds (such as epoxy resin + glass fiber), by contrast, have a thermal expansion coefficient of ≤1.5×10⁻⁵/℃, dimensional stability 10 times higher, and a service life exceeding 300 uses. For complex curved surfaces with a minimum radius of curvature R≤500mm, the machining precision of wood cannot meet the ±0.1mm profile requirement, whereas five-axis CNC-machined resin molds can achieve micron-level precision control.

Production efficiency and economics compared. Traditional wooden mold making relies on craftsmen's experience, with a single set of complex curved-surface molds taking 7-15 days; digital molds, through integrated CAD/CAM, shorten the cycle to 3-5 days. In the Hainan Changying Global 100 Park project, 127 sets of special-shaped molds were digitally designed and manufactured, cutting total cost by 40% compared with traditional wooden molds, while digital management of the mold library laid the foundation for reuse in subsequent projects. Qinglong Group's fully digital mold production line has reduced the mass-production cost of free-form GRC panels by 35% and shortened delivery times by 50%.

Technological development drives industrial upgrading. With the widespread adoption of BIM technology and 3D scanning, the complexity of designed curved surfaces continues to grow, and traditional wooden molds can no longer match modern architectural demands. The German five-axis CNC machining centers introduced by Qinglong Group enable seamless conversion from “design model - machining code - physical mold,” allowing master-level curved designs by the likes of Zaha and Gehry to be realized with precision. In the Shanghai Century Plaza light-transmitting double-curved panel project, digital mold technology kept the deviation between the theoretical surface and the physical product within ±0.5mm, demonstrating how modern mold technology underpins the realization of architectural art.