Causes for Uneven Outer Diameter in Cable Extrusion

What causes inconsistent outer diameter and bamboo-joint defects during cable extrusion? Details below:

Manifestations

Fluctuating screw or haul-off speeds creating diameter variations;
Sudden haul-off instability forming bamboo-like joint patterns in plastic layers;
Undersized die selection combined with semi-finished product diameter variations causing uneven plastic thickness.

Causes

Inconsistent pay-off/take-up or haul-off speeds;
Improper die selection for variable semi-finished product diameters;
Unstable screw speed due to:
Irregular main motor rotation;
Loose or slipping drive belts.

Solutions

Regular monitoring:
Screw rotation consistency;
Haul-off speed stability;
Pay-off/take-up synchronization;
Proper die selection to prevent material backflow.