Quill tool

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Quill tools are extrusion tools that are mainly used for sheathing conductors in cable sheathing or hose production during extrusion blow molding. In contrast to a bar mandrel tool, something can be passed through the quill tool (e.g. wire). The melt entering the tool is led around via a distribution channel or a distribution system (several channels) located on the quill. Distribution channel geometries (starting with the most important):

Fig. 1 Conical quill (coiled coat hanger)
  • The optimal quill geometry is that of the rolled-up clothes hanger distributor. [Fig.1] The basis for this is the further developed calculation system for distributor systems for wide slot tools. This concept has been expanded to include conical and cylindrical quills. With this system it is possible:
    • Maintaining a constant throughput over the circumference with the same pressure drop from the tool inlet to the tool outlet on all flow paths
    • Constant shear rate therefore also constant viscosity throughout the tool
  • Ring groove with a large cross-sectional area around the quill, with downstream high flow resistance (parallel guidance). Not suitable for large outlet diameters and thermally sensitive molding compounds.
  • In the so-called heart curve, the melt flow is divided into two partial flows. These should have as long a flow path as possible around the respective quill half before they are brought together again at the end of the quill. The contour of this divider is reminiscent of that of a heart, hence the name. With this geometry, there are two weld lines that can be viewed as mechanical weak points. In contrast to the clothes hanger distributor, the flow around the displacement body is not overflow. Improvements can be achieved by inserting two “offset” heart curves.

Sheathing of electrical cables

Fig. 2 Principle sketch of the pressure casing
Fig. 3 Sketch of the hose sheathing

The sheathing is done according to the pressure or hose principle. In the pressure tool, non-round substructures can be filled to a round cross-section [Fig.2]. With the hose principle, a uniformly thick coating is applied instead, which largely adapts to the specified cross-section [Fig.3]. In general, high adhesive strengths can be achieved with the printing method. In comparison, the hose method allows the sheathing to be peeled off easily (stripping). With the printing method, it is also possible to sheath a cable with 3 or more conductors, whereby all the gaps that arise are filled with plastic. By applying negative pressure to the quill, the adhesive strength can be adapted to the requirements.

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