Causes for Plastic Layer Thickness Deviation in Cable Extrusion

What causes positive/negative thickness deviations in cable extrusion plastic layers? How to resolve them? Details below:

Deviation Manifestations

Unstable screw and haul-off speeds cause ammeter/voltmeter fluctuations, affecting cable diameter and creating plastic layer deviations.
Substandard semi-finished products (e.g., loose steel/plastic tape wrapping) result in uneven surfaces with bumps, ridges, or pits.
Excessive temperature control reduces output, suddenly thinning cable diameter (negative deviation).

Root Causes

Non-round or snaking core/cable with excessive diameter variation.
Semi-finished product defects: poor steel tape joints, loose sleeves, edge curls, oversized joints, or fraying.
Oversized die tip selection causing material backflow and eccentric layers.
Unsecured die-adjustment screws creating reverse threads and layer eccentricity.
Inconsistent screw/haul-off speeds.
Partial blockage at feed throat or screen pack reducing output (negative deviation).

Solutions

Regularly measure cable diameter and layer thickness; adjust immediately upon detecting variations.
Select proper dies, securely fasten adjustment screws and compression covers after calibration.
Monitor screw/haul-off current/voltage; promptly request electrical/mechanical repairs for fluctuations.
Prevent strip materials or contaminants from entering the hopper; immediately remove if detected.