Warp knitting tubular structures

In most load-bearing medical applications, however, warp-knitted structures, which include both weaving and knitting features, will generally be preferred. Specially constructed Raschel machines that have two needle bars and several guide bars are commonly used. The two needle bars, working alternately, contribute to the versatility of the products. The basic principle is that each needle bar produces a flat fabric the two fabrics are simultaneously connected to each other to form a three-dimensional structure. Examples of structures that can be produced are a double-sided, double thickness structure two separate fabrics with different structures and yarns, joined as needed tubular structure, straight or tapered, and with branches and a sandwich or a spacer fabric with filler yarns. 

Both weft and warp knitting machines are able to construct tubular structures. Although circular weft knitting machines can only be used in producing single tubes, flat weft knitting machines with two needle beds and double-needle bar Raschel machines are able to produce single, bifurcated and multibranched tubes. 

Figure 6.11 A schematic illustration of a warp-knitted bifurcated tubular structure.

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