Designing the warp and weft density of the fabric should also be combined with the use of the fabric. For example, the characteristics of silk fabrics are light, thin and transparent. In order to maintain this feature, in addition to the use of finer warp and weft threads, the warp and weft density should also be reduced. In order to keep the fabric with good elasticity, not weak, not split, the warp and weft density should be balanced as much as possible, and give more twist to the warp and weft. For another example, when designing trumpet silk, in order not to affect the sound quality and maintain excellent air permeability, the density of warp and weft should also be reduced as much as possible. Another example is the decorative silk used for various decorations, such as silk for Chinese painting, fabric for book binding, wall silk, brocade for gift boxes, etc. Under the premise of ensuring the decorative effect, the density of warp and weft can be greatly reduced. On the contrary, the silk taffeta used to make high-end dresses usually has a higher density than ordinary plain weave fabrics in order to make the fabric hard and stiff, and fully reflect the unique "silk sound" characteristic of real silk.
The theoretical density can be calculated based on the interweaving of the thread diameter and the weave structure (wool fabrics have been introduced), but this calculation density is not completely practical, because the production conditions of each production unit are different, and the above five pairs of density design Influencing factors make the actual density a certain difference.
In the actual production process, the weft density of the fabric is smaller than the warp density, mainly because: the raw materials used for the warp threads are better, the tension on the machine is large, the threads are smooth, and the mercerization is sufficient, which has a great impact on the texture of the fabric. And the thread density of warp is generally thinner than that of weft, which is conducive to improving production efficiency. At the same speed, the weft density is small and the output is high. In addition, the small weft density is convenient for production, and it is convenient to remove the weft when weaving defects occur.
The ratio of warp density to weft density should be determined according to the linear density of the warp and weft, the organizational structure and the use characteristics of the fabric. For example, the ratio of warp and weft density of georgette is very close, generally not less than 10%, and the density of satin fabric is very high. The ratio of warp and weft density differs by 50%-60%.
From the design of new varieties, if there are no special requirements, the weft density of plain weave should be 20%-30% less than the warp density, 30%-40% for twill, and about 50% for satin.
If the weft density of the single-layer fabric is greater than the warp density, it is unreasonable and should be avoided. However, heavy-weft fabrics, especially jacquard fabrics composed of multi-color wefts, may have a higher weft density than warp density, which is a structural requirement and can be handled as a special case.