Plastic pelletisation is a critical component of the circular economy, transforming waste plastic into valuable, reusable resources. However, the production process is not always smooth sailing. Understanding common issues in plastic pelletisation and their solutions is an essential skill for every operator and production manager to improve efficiency and ensure pellet quality. This guide combines domestic and international practical experience to systematically analyse these issues and provide practical solutions.

Why is it important to address common issues in plastic pelletisation?  

Ignoring minor issues during production can often lead to major problems. From poor pellet appearance to frequent equipment downtime, these common issues in plastic pelletisation not only directly result in economic losses but also impact the performance and market acceptance of the final product. Timely identification and proper handling of these issues are prerequisites for ensuring stable and efficient production line operation and the continuous production of high-quality recycled pellets.

Analysing the three major categories of common issues in plastic pelletisation and their solutions  

We have categorised the most common issues into three types: pellet quality issues, production efficiency issues, and equipment operation issues.

1. Poor pellet quality  

This is the most obvious issue, directly affecting the product's price and application scope.  
Issue: Rough particle surfaces with pores  

• Cause Analysis: This is typically caused by moisture or volatile substances (such as ink or adhesive) in the raw material not being fully removed, leading to vaporisation at high temperatures. This issue is particularly common in printed film waste from cast film extrusion line.  
  Solutions:  
• Pre-dry moist raw materials.
• Ensure the granulator's vacuum exhaust system is functioning properly and exhaust ports are unobstructed.
• Appropriately reduce processing temperature and extend material residence time in the exhaust section.
• Issue: Black discolouration and burn marks on particles

Cause Analysis: This is a typical indication of localised overheating and degradation of the material. Causes may include excessive temperature settings in a specific zone, accumulated carbon deposits on the screw and barrel due to prolonged lack of cleaning, or filter blockage leading to excessive backpressure.

Countermeasures:

• Inspect and calibrate the temperature sensors in each heating zone, and appropriately lower the set temperature.
• Regularly shut down the machine for thorough cleaning of the screw, barrel, and die head.
• Timely replace clogged filters to maintain smooth melt flow.

2. Low production efficiency

Equipment not running smoothly and low output are among the most frustrating issues for factories.
Issue: Reduced extruder output and feeding difficulties
Cause analysis: For lightweight, fluffy materials, such as scrap from stretch film machine or cling film rewinding machine, the feed opening is prone to ‘bridging,’ causing feeding blockages. Additionally, screw wear or excessive temperature in the feed section can cause premature softening and adhesion of the material, leading to reduced output.

Solutions:  

• Use a feeder with forced feeding or compaction functionality.  
• Check if the cooling water in the feeding section is functioning normally.  
• Regularly inspect the wear condition of the screw and barrel, and repair or replace them as necessary.

Issue: Frequent breakage during strand cutting
Cause analysis: Insufficient melt strength is the primary cause, which may be due to excessively high processing temperatures causing the melt to become too thin, or poor raw material performance.
Solutions:

• Appropriately reduce the temperature of the die head and the rear section of the barrel to increase melt strength.
• Reduce the distance between the die head and the cooling water tank.
• Check if there have been changes in the raw material batch.

3. Equipment Malfunction

Issue: Unstable host current
Cause Analysis: Uneven feeding is the primary cause. Additionally, malfunctioning of the main motor or a faulty heater causing temperature fluctuations can also lead to current fluctuations.
Solutions:

• Ensure even and continuous feeding.
• Check all heating coils and temperature controllers for proper operation.
• Inspect the bearings and transmission system of the main motor.

Quick Troubleshooting Table for Common Plastic Pelletising Issues

The table below summarises common issues to help you quickly identify and resolve them.

Conclusion: Systematic troubleshooting and prevention are key

Resolving common issues in plastic pelletising requires a systematic approach rather than a reactive ‘band-aid’ solution. From raw material pre-processing to proper operation of equipment (such as professional plastic shredder granulator), and regular maintenance and servicing, every step is critical.
As emphasized by the authoritative industry media Plastics Technology, the stability of the extrusion process is the foundation of high-quality production. Therefore, in addition to mastering the above solutions, providing professional training for operators and establishing a strict equipment maintenance and inspection system are the best ways to fundamentally reduce issues and improve overall operational efficiency.