Isolating / Extruding

In the wire and cable industry the extrusion process is the covering with an endless plastic or rubber jacketing. This jacketing can isolate common wire jacketing, protective sheathing or sheathing.

Main machine unit is the extruder. The extruder is a machine which is usually taking granulate and continuously pressing through a foaming tool. The mass is heated, compressed, plastificated and homogenized. Depending on the process and the product the mass is chemically converted, degassed or fumigated.

Depending on the measurements of the tools (tip and die) referring to the measurements of the product and the position at the extrusion head the following difference is made:

  • Pressure extrusion. In this method the bore diameter of the tip is equal or smaller to the outer diameter of the product. The mass speed when leaving the tip is equal or higher than the product speed. The mass pressure and the product speed is very high. This method is particularly suitable to fill crotch and unevenness.
  • Inversion lining method. The diameter of the tip is bigger than the outer diameter of the product. The mass speed when leaving the tip is smaller than the production speed. The tip is forming a hose and the mass of the required wall thickness is stretched. Using this process the insulation is going smooth on top of the product. Coaches and unevennesses will not be eliminated.

A special case is the insulating of the sector shaped cables.

Extruders in the wire and cable industry are usually one screw extruders. A typical design consists of screw, cylinder and heating.

Screw
The screw has one or more helical webs and is turning in a heated cylinder. The screw is fixed in the gear block on one side. The drive is made by means of steplessly adjustable electric motor and reduction gearbox.

Cylinder
The cylinder has an entrance area with an opening where the granulate is fed inside. The heating of the cylinder for extruder operating with thermoplast is made by heating and cooling units. Usually used are heating elements and cooling fans. Our delivery program includes extruders from ø 30 mm to ø 150 mm with a length of 20 – 30 x D. Besides from single extruders we can deliver entire extrusion lines.