Reasons for defective outer sheath of cables

Reasons for defective outer sheath of cables

During the production of cables, the appearance of bulges or slubs on the surface of the cable sheath can be attributed to several factors related to the materials used, the extrusion process, and equipment settings. Here are the primary reasons:

1.Material Contamination or Degradation: If the polymer material used for the sheath is contaminated with foreign particles or has degraded due to improper storage, it can lead to inconsistencies during extrusion, resulting in bulges.

2.Inadequate Material Mixing: The resin and other components must be thoroughly mixed before extrusion. Poorly mixed material can lead to uneven flow through the extruder, resulting in variable thickness and bulges on the surface.

3.Incorrect Extrusion Settings: The settings of the extrusion equipment, including temperature, pressure, and speed, need to be precisely controlled. If the extrusion temperature is too high or too low, or if the pressure is uneven, it can cause the material to extrude unevenly, creating bulges.

4.Air Entrapment: Air can become trapped in the material during the extrusion process. As the material cools and solidifies around these air pockets, bulges can form on the surface of the sheath.

5.Crosshead Alignment Issues: The crosshead in the extrusion process directs the polymer material around the conductive core. Misalignment or uneven wear on the crosshead can lead to improper application of the sheath material, causing bulges.

6.Cooling Process Issues: The cooling process needs to be consistent. If sections of the cable cool at different rates, it can lead to uneven contraction of the material, resulting in bulges or slubs on the sheath.

Identifying the specific cause of these defects requires a close examination of the production process, from raw material handling to the final extrusion and cooling stages. Remedies may involve improving material quality, adjusting equipment settings, or recalibrating the cooling process. Regular maintenance of the equipment, strict quality control of materials, and proper operator training are essential steps to minimize the presence of these defects.