In wire and cable production, temperature control accuracy during the extrusion process is a key factor affecting product quality and production efficiency. Temperature control not only directly determines the physical state and flow characteristics of the plastic but also permeates the entire extrusion process—plasticization, molding, and finalizing. Inadequate accuracy can lead to degraded material properties, cosmetic defects, and even equipment failure.
During the plasticization stage, temperature is the key driver for the plastic's transformation from a granular solid to a viscous, fluid melt. If the temperature is too low, the plastic cannot fully melt, resulting in excessive melt viscosity and excessive axial force during extrusion, potentially causing equipment overload or screw damage. For example, polyvinyl chloride (PVC) is prone to forming unmelted particles at low temperatures, leading to defects such as lumps and small particles on the insulation or sheathing surface, compromising the product's electrical performance and mechanical strength. Conversely, if the temperature is too high, the plastic may thermally decompose, producing charred materials or bubbles, which not only reduce the material's insulation properties but also release harmful gases, threatening production safety.
The molding stage places even more stringent demands on temperature control accuracy. As the melt is extruded from the die, it must form a continuous, uniform layer through the die. Uneven die head temperature distribution can lead to localized overheating, causing variations in melt flow, resulting in excessive outer diameter deviations in the extruded wires and cables, and even core deviation. For example, uneven insulation thickness in high-voltage wires and cables can cause electric field concentration, increasing the risk of breakdown. Furthermore, temperature fluctuations can affect the quality of the glue seams, leading to sheath delamination or bubbles, and reducing the product's protection level.
The final stage of temperature control precision is the final hurdle. The extruded plastic layer must pass through a cooling water tank to rapidly solidify and maintain a stable shape. If the cooling water temperature is too high, the plastic layer may deform due to incomplete solidification. If the water temperature is too low, the sudden cooling may cause residual internal stress, leading to cracking in materials such as polyethylene (PE) and cross-linked polyethylene (XLPE). For example, rapid cooling of PVC sheaths can improve finalizing efficiency, but the water temperature must be strictly controlled to avoid large temperature differences that can reduce surface gloss or cause fine cracks. Materials such as PE and XLPE require a slow cooling process, which reduces internal stress through staged cooling to ensure long-term product reliability.
Temperature control accuracy is also crucial to equipment stability. The gap between the extruder's screw and barrel is extremely small. Improper temperature control can cause plastic melt to backflow or leak through the gap, increasing equipment wear and energy consumption. For example, too low a screw temperature increases melt viscosity, exacerbating friction between the screw and barrel and shortening equipment life. Excessively high temperatures can cause plastic scorching, clogging molds or filters, and disrupting production. Furthermore, inaccurate cooling systems can cause barrel temperature fluctuations, impacting extrusion output stability and leading to out-of-tolerance outer diameters or jacket thicknesses in wires and cables.
Based on their material properties, different plastics exhibit significant differences in their sensitivity to temperature control. Polyethylene (PE) has a wide melting point range and a relatively large temperature control tolerance. Polyvinyl chloride (PVC), on the other hand, has a narrower stable temperature range and requires the addition of stabilizers to enhance thermal stability, placing higher demands on temperature control accuracy. Temperatures outside the material's tolerance range can cause premature crosslinking (as in the case of XLPE) or reduced foaming (as in the case of foamed products), resulting in product performance that fails to meet standards.
Temperature control accuracy also directly impacts production efficiency and costs. Precise temperature control shortens plasticizing time, increases extrusion speed, and enables high-speed production. For example, by optimizing the temperature gradient between the barrel and die, the melt's residence time within the equipment can be reduced, preventing decomposition due to overheating or insufficient plasticizing due to low temperatures. Furthermore, stable temperature control reduces scrap rates, raw material waste, and rework costs, thereby improving overall production efficiency.
In wire and cable production, temperature control accuracy in the extrusion process is crucial for ensuring product quality, equipment stability, and production efficiency. From uniformity during the plasticizing stage to dimensional accuracy during the molding stage and structural stability during the finalization stage, every detail of temperature control directly determines the final product performance.
