The moisture content of the wood box is within the fiber saturation point of the wood, and the bending property of the wood increases with the increase of the moisture content of the wood. When the density of the wood is small, the moisture content can be appropriately larger, because the density of the wood is small and the moisture content is easy to be removed.

The temperature of wood material increases with the increase of wood temperature, but when the temperature of wood is too high, the plasticity of wood increases and the hemicellulose in wood degrades, which reduces the strength of wood.

After the bending speed is softened, the straight-line square timber must be bent immediately. If the bending speed is too slow, the temperature of the wood will be reduced, and the plasticity will be weakened, which will affect the bending performance of the wood; if the bending speed of the wood is too fast, the internal structure of the wood will not be able to adapt to the needs of deformation, resulting in damage.

The relationship between ring layer and bending surface when the ring layer of wood is parallel to the bending surface, the wood will not be damaged under large pressure; however, when the ring layer is perpendicular to the bending surface in the same year, under the bending pressure, the ring layer is prone to slip, reducing the bending performance of wood.

When the thickness and width of the straight-line square timber are large, the wood is easy to lose its stability when it is bent. Therefore, the width of the square timber can be used in the actual production to make multiple pieces of wool. When the straight-line square timber is bent, it can be split.