On the importance of selvage
In the entire process of natural cotton production, the selvedge plays an extremely important role. During the weaving process, the edges of the fabric must be fastened to both ends of the weft yarns to withstand the strong force of the temple braces, so that the fabric surface does not produce excessive weft shrinkage, reduce the bending of the edge warp yarns, improve the friction between the edge warp yarns and the reed teeth, and reduce the friction between the edge warp yarns and the reed teeth. The edge warp breakage rate increases the edge strength, keeps the cloth surface flat, and has a consistent effective width. It is also easy to wind and form well, which is convenient for post-process finishing.
During the dyeing and finishing process, the edge of the fabric is also subject to the pulling force of cloth clips or needle punching, especially for cellulose fiber fabrics such as cotton and linen. Withstand great pulling forces. Therefore, a firm, flat, and appropriately tight edge structure is a necessary condition for finishing. Unreasonable edge design will cause the fabric to have loose edges, broken edges, tight edges, curled edges, etc. In severe cases, a large number of broken edges will occur, and even post-processing will be impossible, causing huge losses.
In shuttle looms, the weft yarn is alternately inserted on both sides through the shuttle to form a complete edge; while in rapier looms and air-jet looms, the weft yarn is unwound through the package at high speed and the weft is inserted in one direction. Both sides of the weft yarn are free ends, and then the raw edges are formed. In the middle part of the fabric, the weft yarns have a greater degree of buckling and are relatively uniform, while the two sides of the fabric are free ends and are mainly held by the seams and false edges. If the edge design is unreasonable, the tension of the weft yarns at the edges will be greater than that of the fabric body. The tension of the weft yarn is much smaller and the weft yarn is loose, which will cause weft shrinkage, and the shrinkage rate of the warp yarns at the edge and the warp yarn of the cloth body will be quite different, which will bring hidden dangers to the subsequent processes.
Generally, twill and forged weaves use borrowed edges, that is, a single piece of heddle and weaving are woven together. The pattern plates must be opposite, such as 4/1 edge and 1/4 of the ground weave, and the weave points are opposite. Jacquard weave, joint weave, etc. are accustomed to use heavy flat and square flat edges, and consider the following four aspects:
1) Width
The edge structure is too narrow and not strong enough to withstand the pulling force. It is easy to tear the edge and cannot protect it. If it is too wide, it increases the cost of the fabric and affects the cuttable area of the fabric under the condition that the effective width is certain. Generally speaking, a simple weave fabric only needs a smaller width, but the edge width of some same-face, different-face weaves and stretch fabrics with longer floating lines should be appropriately increased according to the situation.
2) Thickness
The edge thickness should be exactly the same as the fabric body, so that it is easy to keep the fabric flat, winding, beautiful, and evenly stressed.
3) Tightness
The edge of the fabric is usually slightly tighter than the body, but certainly not too tight. Too tight will affect the finishing, because the edge of the fabric cannot withstand large deformation in a short period of time, and may even tear the edge of the fabric, making the entire batch of fabrics useless. It won’t work if it’s too loose. On the one hand, it will cause weft shrinkage and ruffles, which will easily break during finishing. Therefore, the density of edge tissue is greater than that of ground tissue.
4) Heald threading and reed threading
The number of healds used for the edge should be as small as possible. It is easier to organize the heald frames to make the edges. Usually two more pages of healds are added, otherwise it will increase the difficulty and cost of weaving. Drawing on healds and reeding are mainly based on The organizational structure of the edge and its required functions should be designed to achieve the requirements and functions of the edge. The number of reeds for the edge tissue should usually not be less than the number of reeds for the ground tissue. For varieties with more than 8 pages, it is best to place the edges on the first two pages to ensure clear edge openings and reduce the number of weft stops.
5) Suggestions
Make 4/1 elastic fabric. If you use a dobby machine, it is recommended to use 2/2 square. For stability, it is recommended to use 2/3+3/2 single wear when using a pedal. Compared with 1 /4+4/1 is not easy to curl. You can also “add keel ribs” in the 2/3+3/2 selvage, which is also helpful to overcome the curling caused by the large difference in the latitude and longitude tissue points of the two sides.
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