Double-needle bar Raschel machines

Production of flat fabrics and branched tubular structures with various geometries can be produced at the RWTH-ITA with the help of a special double-needle-bar Raschel Machine (Figure 3, Type DR 16 EEC/EAC Karl Mayer Textilmaschinenfabrik GmbH, Oberfaausen, Germany). Fields of application are e.g. keratoprosthesis (artificial cornea), vascular grafts, heart-valves, hernia-meshes and stents. 

Figure 6.4 A double-needle bar Raschel machine (Jakob Miiller MDK80).

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. 

Similar to a computerised flat knitting machine with two needle beds, a double-needle bar Raschel machine has two needle bars. It is possible to knit tubes of different sizes on such a machine with a set of fully threaded guide bars to knit two separate fabrics... 

Figure 6.22 Principle of producing spacer fabrics on a double-needle bar Raschel machine (a) a schematic illustration and (b) RD 6 by Karl Mayer.

Warp-knitted spacer fabrics are produced on double-needle bar Raschel machines the principle is schematically shown in Figure 6.22(a). While the guide bars 1 and 2 lap the front-needle bar, and the guide bars 5 and 6 lap the back-needle bar, to knit the top outer layer and the bottom outer layer, respectively, the guide bars 3 and 4 lap the spacer yams around both the needle bars in succession. A spacer fabric being produced on a double-needle bar Raschel machine RD 6 by Karl Mayer is shown in... 

Spacer warp-knitted NCFs are produced with double-needle bar raschel machines. The machine has symmetric build-up warp-knitting elements (Fig. 8.14). 

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