Woven fabrics are formed by interlacing warp and weft yarns on a weaving machine. During the weaving process, there is repeated vertical and horizontal friction and bending occur between warp yarns and warp yarns, between warp yarns and weft yarns, and between warp yarns and various objects on the weaving machine.
The weaving preparations are indispensable for making the yarn have sufficient strength, wear resistance, and elasticity, ensuring that the yarn will not be broken due to the various destructive forces during the weaving process, and improving production efficiency and obtaining excellent products.
It is necessary to prepare warp and weft yarns before weaving to increase the package length of yarn and facilitate continuous production, and improve the technical performance of warp and weft yarns.
Main Steps of Weaving Preparation
The winding process is carried out on the winding machine, to continue the spun bobbins obtained in the spinning process for making the yarns obtain proper and uniform tension.
According to the required standard, we need to check and remove the defects such as uneven knots, impurities, and dust on the yarns, but other small but firm knots will be generated during the removal process. Then a winding machine is used to wind the bobbin with uniform density, sufficient capacity, good shape, and ease to unwind.
Warping needs to be processed on the warping machine. It is to draw a piece of yarn out from the beam on the creel behind the warping machine according to the number of warp yarns specified in the process design and to make sure that the tension between yarn roots, yarn pieces, and between front yarn and the back yarn is uniform according to the length and width specified in the design. And under appropriate conditions, the yarn sheets will be wound in parallel to form a well-formed warp beam.
Sizing is a key process in preparation for weaving. The main purpose of sizing is to improve the weave capability of the yarn, and at the same time, the slashed yarn sheet is wound into a well-formed weaving beam under the condition of uniform tension, uniform arrangement, and uniform winding density.
Three Aspects Performing Weaving Ability of Yarns
Through the sizing process, a portion of the sizing solution penetrates into the yarn, reducing the possibility of slipping between fibers inside the yarn, thus increasing the yarn strength and improving the ability to withstand tensile and impact loads.
3.2 Keep Elasticity
In the process of sizing and drying, the elasticity and elongation of the yarn are maintained to avoid the occurrence of yarn breakage during weaving due to brittleness and stiffness.
3.3 Reduce Friction
A part of the sizing liquid is covered on the surface of the yarn to form a layer of size film, and the fluff on the yarn surface is attached to the yarn stem to reduce the friction between the yarns and between the yarn and the machine parts coefficient, so that improve the ability of yarn friction resistance.
4. Warp Drawing-in & Warp Knotting
This is the last process of warp yarn preparation before weaving. The yarn is drawn from the weaving shaft and passes through the warp stopper, heddle hole, and reed tooth one by one according to certain weaving sequences of fabric design. Thus, it can be opened into a shed during weaving and incorporated into the weft yarn, then can be woven into a fabric with a certain width and warp density.
The traditional drawing-in method is done manually with the help of a semi-automatic drawing-in machine. However, a fully automatic drawing-in machine is necessary to connect the warp yarns on the new and old weaving beams one by one during the mass fabric production line.
5. Weft Winding (Rewinding)
Weft winding is the weft yarn preparation process before weaving, for rewind the weft yarn has changed the package shape on the weft winder to make it meet the weaving requirements, with suitable density and proper shape, uniform tension, and ease to unwind. Some yarn defects will be removed to improve the quality of the weft yarn at the same time.
During the weaving process, when the weft yarn tension is too small and the weft yarn twist is large, or due to the strong reverse twist force of the weft yarn, weft shrinkage and looping may occur. To avoid this kind of occurrence and to reduce the weft yarn twist and increase the unwinding tension of the weft yarn, it is often used to wet and heat the weft yarn to fix the twist.