1. Spiral cable plastic scorch
Plastic scorch is a common quality defect in the plastic extrusion process, and its main manifestations are: the temperature is extremely high; the extruded plastic layer has coke particles; there are continuous bubbles at the glue joint. The main reasons for this are: the temperature control is as high as the thermal degradation temperature of the plastic; the screw has not been cleaned for a long time, and the accumulated scorch is extruded with the molten plastic; the heating or shutdown time is too long so that the plastic in the barrel will be decomposed by long-term heating. ; The temperature control instrument is out of control or inaccurate, causing high-temperature decomposition.
2. Poor plasticization of the extrudate
The problem of plasticization has been mentioned in the temperature control requirements mentioned earlier. Generally, poor plasticization is mainly manifested as the surface of the extruded plastic is black, dull, and there are small cracks; the extruded layer has obvious signs on the glue. Seam; unstandardized temperature control of spiral cable is the main cause of poor plasticization of extrudates, including temperature control is too low; other plastic particles of different properties are mixed in the insulation or sheath material; the screw is turned too fast, The plastic has not been completely plasticized; the plastic itself has quality problems.
3. There are pores or bubbles in the section of the squeezed layer
The main reasons for the formation of pores or bubbles in the extruded layer section include: excessive temperature control (especially in the feed section); plastic damp and moisture; long-term parking, decomposing the plastic but not removing it; high humidity in the natural environment; inside the cable core The content of water or vapor is too high.
4. The squeeze package size is unqualified
The unqualified size of the extruded package is mainly manifested as eccentricity, sheath thickness, and outer diameter out of tolerance. The main reasons are as follows: the extrusion and traction speed is unstable; the outer diameter of the cable core changes too much; the extrusion temperature is too high and the extrusion volume is reduced; too many impurities in the plastic block the filter screen to reduce the plastic flow; The tension of the thread is unstable; the mold core is selected too large (extrusion type) or the length of the core line area is too short and eccentric; the mold spacing is not selected properly; the temperature of the extruder head is uneven; the concentricity of the extrusion die Not adjusted well; the temperature of the feed inlet is too high to make the feed difficult to affect the material flow and so on.
5. Adhesive strength of longitudinal tape is unqualified
The main reasons for the unqualified bonding strength of the longitudinal tape of the spiral cable are: the temperature of the extrudate is too low; the speed of the production line is too fast so that the sheath is rapidly cooled; the temperature of the hot water tank is too low and it is close to the die; The stretch ratio is too small, or the mold matching is unreasonable, causing it to form a loose package; the melting point of the composite film with longitudinal tape is too high;
6. The appearance of the squeeze package is unqualified
The unqualified appearance of the extruded package is mainly manifested as scratches on the surface of the extruded layer; the roughness of the spiral cable with trachoma or microcracks; any defects caused by poor plasticization. The main reason is: the choice of extrusion die sleeve is unreasonable. Impurities in the extrusion die sleeve are stuck and scratch the surface of the sheath. The excessive heating temperature of the extruder head causes roughness or too low-temperature causes micro-cracks; the die sleeve sizing area is damaged; the sheath is scratched in the sink, etc.
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