In cable extrusion, the screw melts the insulation or sheath material and conveys it to the head. Over time screw and barrel wear, and the line loses output.
How to recognise wear
Filled compounds, such as halogen-free flame-retardant compounds with a high filler content, are abrasive. The clearance between screw flights and barrel wall grows, material flows back, output drops and melt temperature rises. This often first shows as fluctuating wall thickness or higher energy demand.
The outer diameter of the flights is measured at several points, as is the inner diameter of the barrel. Hard-faced flights and bimetallic barrels last longer. Worn screws can often be re-hard-faced and ground if the core is in good condition.
What a request for screw or barrel should contain
- screw diameter and length or L/D ratio
- drawing or extruder type
- materials processed
- measured values of flights and barrel, if available
- new part or refurbishment
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