The forming fabrics or "nets" of a paper machine are continuous belts or mesh belts on which paper is formed. Most modern forming fabrics no longer consist of metal wires. Instead, they consist of monofilament polyester strands. The weaving patterns and layering of forming fabrics are designed to meet the stringent requirements of dimensional stability, abrasion resistance (on the wire side), minimum drainage resistance, minimum wire traces and (sometimes) maximum retention of fine fiber particles. The traditional Fourdrinier paper machine only has one forming fabric. Paper machine forming fabrics are designed to retain as many fibers and other ingredients as possible while allowing water to drain through them as quickly as possible. These forming fabrics are usually made of monofilament strands or yarns, which are woven together in patterns that can be classified by fabric style (or weave); mesh number, number and diameter; surface topography; and air permeability.
What are the two main tasks of forming fabrics?
Keep as much fiber and other ingredients as possible, and let the water drain out as quickly as possible.
What are the most common fabric patterns or structures in forming fabrics?
Single layer (one MD and one CD thread) forming fabrics: In plain weave fabrics, the warp yarns are composed of yarns during the weaving process, called MD yarns. To make an endless loop, the fabrics are connected by connecting warp yarns at the end of each fabric. PFM Screen uses an automatic stitching machine to join the fabrics.
1.5-layer forming fabrics: This is a 5-shed single-layer fabric woven with extra yarn, giving it the characteristics normally found in double-layer fabrics. The extra yarn provides better paper surface smoothness and better retention. Due to its unique structure, it provides very good drainage and is easy to clean. This structure, generally called 1.5 floors, is FILCON's original design.
Double-layer forming fabrics (one MD and two CD strands):The structure of our double-layer fabrics is generally a double-layer weft structure; the manufacturing method is seam (H) [type]. Compared with a single layer, the warp and weft density is higher. The double layer has higher dimensional stability, but poor stretchability. The diameter and material type of the piece-side weft yarn and the machine-side weft yarn can be selected independently, which can improve thread marks, double-sidedness, flatness and fabric life. Due to the large three-dimensional space (the plane space is almost zero), our double layer also provides excellent drainage performance. Drainage power does not directly affect the paper layer, which helps to increase retention and prevent lint.
2.5-layer forming fabrics("EX" weaving): In order to further improve the characteristics of the double-layer design, one-sided weft yarn density has been increased. The result is better paper support and improved paper line marks, retention and surface characteristics. In addition, the number of wefts on the machine side is reduced, thereby increasing the three-dimensional space (void volume) and enhancing the drainage capacity. This design is commonly referred to as 2.5-layer weave, or "EX" weave.
Three-layer forming fabrics (two MD and three CD strands): Three-layer fabrics designed by the latest generation of WSB. By increasing the surface yarn density, paper support and retention are improved, while reducing thread marks. FUJI/SAKURA series have low internal abrasion and stable performance until the last stage of fabric life.
What is the difference between "grid" and "count"?
The mesh count refers to the number of MD yarns per inch of fabric, and the count refers to the number of CD yarns per inch of fabric.
Why can't breathability (measurement of air flow) alone be used to predict the drainage capacity of forming fabrics?
Because it does not take into account the influence of fibers and ingredients on drainage. The surface morphology and fabric structure will affect the retention of the fabric, and therefore also affect the dehydration capacity of the fabric.
How to judge whether forming fabrics are misplaced?
Most forming fabrics have colored stripes across their width. If the stripes are not straight, it means the fabric is skewed or misaligned.