Effect of screw wear on production efficiency of conical twin-screw extruder
As the core component of the extruder, the screw plays a key role in the material conveying, compression, melting and plasticization processes. However, after long-term use, the screw will inevitably wear out, which will have many effects on the operation of the equipment and the production process.
1. Material conveying efficiency is reduced
In a conical twin-screw extruder, the screw plays a crucial role in conveying materials. Its thread structure propels the material forward along the barrel through rotation. When the screw wears out, particularly if the thread wears down and the pitch changes, the friction between the material and the screw decreases, reducing the screw's ability to push the material. Materials that were previously conveyed quickly and steadily may now slow down or even stall intermittently. For example, under normal conditions, the screw can transport a certain amount of material from one end of the barrel to the other within a specified time, meeting the production rhythm requirements. However, after the screw wears out, the amount of material transported in the same time period decreases, leading to a reduction in the overall discharge speed of the extruder and a decrease in production efficiency.
2.the deterioration of plasticization effect leads to production interruption
Another key function of the screw is to blend and plasticize materials, ensuring they reach a uniform molten state under heat and shear. However, a worn screw cannot provide stable and effective shear force or blending effect. This results in incomplete plasticization of the material inside the barrel, leading to partially unmelted particles or uneven plasticization. When these substandard materials are extruded, they can cause product quality issues, such as rough surfaces and internal bubbles. To ensure product quality, frequent shutdowns and adjustments to process parameters are necessary during production, and even rework on already produced substandard products is required. Frequent shutdowns and rework significantly reduce production efficiency, increase production time, and raise costs.
3. The fluctuation of extrusion pressure affects the stability
Screw wear alters the gap between the screw and the barrel, affecting the material's flow resistance within the barrel and causing abnormal fluctuations in extrusion pressure. This instability can cause the extrusion speed to fluctuate, making it difficult to maintain a steady production rhythm. For example, a sudden increase in pressure can overload the motor, forcing the equipment to shut down; if the pressure is too low, it can result in insufficient material extrusion, failing to meet production needs. This unstable production state not only reduces output per unit time but also increases the workload for operators to monitor and adjust the equipment, further impacting production efficiency.
4. The risk of equipment failure increases and the downtime time is extended
As the wear on the screw intensifies, it can lead to a series of equipment failures. For example, metal fragments from the wear may enter the bearings and transmission components, exacerbating their wear and potentially causing jamming. Uneven wear between the screw and the barrel can also cause abnormal vibrations and noise during operation. When equipment malfunctions, it must be shut down for maintenance and component replacement, leading to prolonged production interruptions. Compared to normal production, frequent equipment failures and repairs significantly reduce effective production time, severely impacting the production efficiency of the conical twin-screw extruder.
