| The development of physical foaming of PE and FEP during the last few years, superseding chemical foaming, meets the growing requirements for higher data transmission frequency with comparable or even smaller product dimensions. The extrusion technology of three extruders for the production of physically foamed �Skin Foam Skin� core is now common practice within the industry. The quality, productivity and efficiency of the core line focuses on the specific know-how of the cable maker and attention to detail, i.e the crosshead, where key words are concentricity, ovality, production speeds, easy handling, and quick tool change times.
Specialising in the construction of extruder crossheads and tools, CJTEK, Switzerland, has recently launched a new 3-layer crosshead for physical foaming suitable for the production of high-quality data cables and which permits a stripe mark (e.g., as a substitute of the ring marking) without a fourth extruder. The system is particularly suitable for the production of LAN products, as well as for medium and large foam cross sections and provides high-quality standards regarding concentricity (> 97%) and high-production speeds, working on a three-shift operation year after year. The new crosshead does not need any additional extruder for the stripe. The material flow of the internal skin is divided in the crosshead in a suitable form, so that a part of the material can be used for the external stripe. For this process, the material for the internal skin is coloured. The internal skin will show a defined wall-thickness and the stripe will not deform the external skin or influence the electrical characteristics of the final product. Furthermore, the new crosshead is adaptable to all existing skin/foam/skin extrusion groups and can be used alternatively for foam-skin, skin-foam, skin-foam-skin, skin-foam-skin + stripe.
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