How to effectively solve the problem of material blockage in the use of Conical Screw Barrel?

In the fields of plastic extrusion, granulation and pipe production, Conical Screw Barrel is widely used due to its high output and stable plasticizing performance, but the problem of material blockage often leads to shutdown, increased energy consumption and even equipment damage.
Cause of blockage: In-depth analysis from material characteristics to equipment design
Material blockage is usually caused by three factors:
Material characteristics: high viscosity (such as PVC), excessive humidity or impurities (such as recycled materials that are not fully dried) are easy to adhere and agglomerate in the screw gap;
Equipment design defects: unreasonable screw compression ratio, substandard barrel inner wall roughness (Ra＞0.4μm) or insufficient temperature control system accuracy, resulting in uneven local melting;
Process parameter mismatch: speed and feed rate are not coordinated, and shear heat accumulation causes material degradation and carbonization.
Taking PVC processing as an example, when the material humidity is ＞0.05%, water vaporization is easy to form bubbles in the barrel exhaust section, aggravating material accumulation.
Core solution: process optimization and equipment upgrade in parallel
1. Targeted design of screw and barrel
Step compression ratio optimization: For highly filled materials (such as WPC with more than 30% calcium carbonate), a progressive compression design is adopted to avoid material retention caused by sudden pressure changes. For example, the traditional 3:1 compression ratio is adjusted to a multi-stage 1.5→2.5→3.5, which significantly reduces the risk of bridging.
Bimetallic surface treatment: The inner wall of the barrel is centrifugally cast with iron-based alloy (hardness HRC62-66), and the screw surface is sprayed with tungsten carbide (thickness ≥2mm) to reduce adhesion and improve wear resistance, which is suitable for glass fiber reinforced materials.
2. Intelligent sensing and automatic control
Integrated paddle level switch: Install sensors at key positions of the barrel to monitor the flow status of materials in real time. When the stacking height triggers the threshold, the vibration motor is automatically started or the feeding speed is adjusted to prevent blockage from worsening.
Temperature control system upgrade: PID algorithm is used to dynamically adjust the power of the heating ring to ensure that the barrel temperature fluctuation is ≤±1.5°C, avoiding carbonization and wall adhesion caused by local overheating.
3. Material pretreatment and process parameter matching
Humidity control: By adding a drying hopper to the feeding section of the twin screw, the material humidity is stabilized below 0.02%;
Particle size screening: The recycled material is graded and crushed to ensure that the particle size distribution is concentrated in the 2-4mm range to reduce the agglomeration of fine powder.
Maintenance strategy: prevention is better than remediation
Regular cleaning and coating maintenance: Use special cleaning materials (such as PP-based purging compound) to clean the barrel every 500 hours of operation, and check the integrity of the nitriding layer (depth ≥0.5mm);
Vibration-assisted arch breaking: Install a high-frequency turbine vibrator (frequency 20-60Hz) at the feeding port to destroy the arched stacking structure of the material and improve fluidity;
Data-based operation and maintenance: Record equipment operating parameters (such as torque fluctuations and energy consumption trends) through the Internet of Things platform, predict blockage risks and generate optimization reports.