How to adjust the density of Raschel warp knitting machine?

The warp let-off is the core of density control. The warp beam unwinding speed can be accurately adjusted through the electronic warp let-off system (EBA) or mechanical gear mechanism. When the warp let-off is reduced, the warp tension increases, the coils are tightened, and the longitudinal density of the fabric increases; conversely, increasing the warp let-off reduces the longitudinal density. For multi-bar models, the warp let-off ratio of each bar needs to be allocated according to the fabric design to avoid local over-tightening or over-looseness.

The speed and tension of the pulling roller directly affect the transverse density of the fabric. Increasing the speed of the pulling roller increases the pulling force, the coils are elongated, the fabric becomes thinner, and the transverse density decreases; reducing the speed weakens the pulling force, the coils shrink, and the transverse density increases. Some equipment supports independent tension adjustment in different zones, which can be precisely controlled for different fabric structures (such as mesh and dense areas).

The lateral displacement of the comb determines the span of the coil. The larger the lateral displacement, the looser the coil and the lower the density; vice versa, the density increases. In the double needle bed model, reducing the distance between the front and rear needle beds can squeeze the coils against each other and improve the overall density; increasing the distance is suitable for producing loose or spaced fabrics.

The speed, raw material characteristics, and density adjustment are closely related. When running at high speed, the warp let-off and the pulling tension need to be adjusted synchronously to prevent uneven density due to tension fluctuations. In addition, different raw materials (such as elastic fibers and rigid yarns) have different sensitivities to tension and warp let-off, and the optimal parameters need to be matched through trial weaving. Before mass production, a small sample should be woven first, and the horizontal and vertical density should be measured with a density mirror. After comparing with the design value, it is gradually fine-tuned to ensure that the finished product meets the standard.

If you are interested in learning more about the Raschel warp knitting machine, please contact New Power. Our professional team will provide you with customized solutions and comprehensive technical support.

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