Saliva discharge from the optical cable sheath mold opening

Saliva discharge, or drooling, from the optical cable sheath mold occurs when molten sheath material oozes from the mold, affecting the quality of the outer sheath.Causes of Saliva DischargeSaliva discharge happens primarily during the extrusion of the cable's outer sheath. The molten polymer, such as PVC or PE, has high viscosity and is not fully solidified at the mold exit. When the extruded material contacts the mold opening, it can form droplets or strings, which are pulled along by the advancing sheath . Contributing factors include:Uneven extrusion parameters: Variations in temperature, pressure, or speed can cause inconsistent flow and drooling .Mold design issues: Improper die aperture, worn or damaged molds, or incorrect spacing between inner and outer molds can increase drooling .Cooling inefficiencies: If the extruded sheath is not cooled rapidly or uniformly, the material remains sticky and prone to drooling .Environmental factors: Temperature fluctuations in the workshop can affect the viscosity and solidification of the sheath material .Effects on Cable QualitySaliva discharge can negatively impact the outer sheath by:Creating surface defects such as roughness, bulges, or uneven thickness .Affecting cooling and solidification, leading to poor mechanical and thermal properties .Increasing rework and material waste, reducing production efficiency .Solutions and Preventive MeasuresSeveral strategies can minimize or eliminate saliva discharge:Mold and die optimization: Use molds with appropriate aperture and die bearing length, and ensure molds are in good condition .Temperature and pressure control: Maintain consistent extrusion parameters and improve cooling systems to solidify the sheath quickly .Drool removal devices: Specialized devices can remove drool at the mold exit, preventing it from affecting the advancing sheath .Material handling: Ensure the polymer pellets are dry, properly mixed, and free from contamination before extrusion .Rapid cooling methods: Apply cold water or air cooling immediately after extrusion to stabilize the sheath surface .Advanced TechniquesSome patents describe sheath divest molds and longitudinal opening knives that allow precise control of the sheath during extrusion and post-processing, reducing drooling and improving overall quality . These devices can also facilitate secondary processing of the sheath without damaging internal components, enhancing material efficiency and environmental sustainability . By addressing these factors, manufacturers can significantly reduce saliva discharge, improve the surface quality of optical cable sheaths, and maintain consistent production standards.