Solutions for Production Problems in Plastic Pelletizing Process
During the plastic pelletizing process, various problems often arise, directly impacting pellet quality and the stability of the subsequent extrusion process. The following analyzes common problems and proposes corresponding solutions to quickly identify the issues and optimize production.
I. Pellet Appearance and Morphology
01. Rough, matte, or pitted pellet surface
Poor plasticization: Temperature setting too low or insufficient shear force. Appropriately increase the temperature in the plasticizing and homogenizing sections.
Excessive raw material moisture: The plastic raw material, filler (such as calcium carbonate), or hygroscopic additives are not fully dried.
Improper lubrication system: Excessive lubricant, especially external lubricant, leads to delayed plasticization; the ratio of internal and external lubricants is unbalanced.
Equipment Problems: Excessive extruder screw wear, insufficient compression ratio, or insufficient shear force.
Insufficient die pressure: The extruded melt is not dense enough. Use a finer mesh filter, adjust the die pressure bolt, or slightly reduce the feed rate.
02. Pellets Sticking
Insufficient Cooling: The cooling water temperature is too high or the cooling time is too short, resulting in incomplete cooling of the pellet center. It is recommended to lower the cooling water temperature (recommended 10-25°C), extend the cooling water tank length, or adopt a more effective cooling method.
Static Accumulation: Excessive static electricity on the pellet surface can be eliminated by installing an ionizing air bar after pelletizing or at the vibrating screen.
Lubricant Issues: Excessive lubricant (especially external lubricant) or precipitation. Select a lubricant with good compatibility and low precipitation resistance.
Cutter Issues: A blunt cutter or improperly adjusted cutter gap results in excessive burrs in the pellets.
High Humidity: The production environment is too humid; reduce the humidity as much as possible.
03. Uneven Pellets with Tailing
Unstable Feeding: Raw material bridging, feeder failure, or fluctuating feed rates.
Melt Pressure/Temperature Fluctuations: Process parameters are unstable; precise temperature control is required to maintain stable melt pressure and temperature.
Speed Mismatch: The pelletizer speed, main engine screw speed, and traction speed are poorly coordinated. Cutter Problems: The cutter is worn and blunt, or the installation is loose. The cutter should be replaced or polished regularly to ensure it is securely installed.
Dieplate Problems: Clogged die holes or uneven wear of the die holes lead to uneven discharge speeds. It is recommended to thoroughly clean the die holes, inspect the wear, and replace the die plate if necessary.
04. Coke Spots on the Pellets
Coke Accumulation in the Screw: The screw has not been cleaned for a long time, causing accumulated coke to be removed. The screw needs to be disassembled and thoroughly cleaned.
Excessive Heating Time of the Material: This causes material aging and coking. It is recommended to shorten the heating time and inspect and repair any heating system faults.
II. Internal Structure and Performance Problems of the Pellets
01. Poor Plasticization (Pellets Contain Unmelted Material or Small White Spots)
Insufficient Temperature: The plasticizing section temperature is set too low. It is recommended to increase the plasticizing section temperature to meet the requirements.
Screw Problems: Improper screw assembly design or severe wear, insufficient compression ratio, and weak shear force. Lubricant Obstruction: Excessive external lubricant hinders the plasticization process. It is best to increase internal lubricant or add additives that promote plasticization.
Short Residence Time: The screw speed is too fast or the feed rate is too high. Appropriately reduce the screw speed or reduce the feed rate to extend the plasticization time.
Poor Filler Dispersion: The filler (such as calcium carbonate) is not fully infiltrated and dispersed. It is recommended to optimize the mixing process to ensure full infiltration and dispersion of the filler.
02. Particles Containing Bubbles or Porosity
High Raw Material Moisture: The plastic raw material, filler, or recycled material contains too much moisture. All moisture-prone raw materials should be thoroughly dried.
Excessive Volatile Matter: The formulation contains volatile components such as low-boiling-point plasticizers and lubricants.
Excessive Processing Temperature: Localized overheating causes slight decomposition and gas production of the material. Avoid localized overheating to prevent thermal decomposition.
Poor Die Design: The melt pressure drops too quickly at the die head. Maintain a gradual drop in melt pressure.
Poor Venting: The vacuum venting system is not open or the vent is blocked. Ensure the vacuum venting system is functioning properly.
03. Poor Thermal Stability (Yellow Pellets, Black Spots, and Yellow Lines)
Improper Stabilizer: Improper selection of thermal stabilizer or insufficient addition.
Excessive Processing Temperature: Overall temperature exceeds standard or localized overheating occurs (temperature control failure, excessive screw speed, shear overheating).
Excessive High-Temperature Dwelling Time: Material retention due to die blockage, overly fine or clogged filter screens. The die should be cleaned and the filter replaced regularly to avoid prolonged low-speed operation.
Material Accumulation in Equipment Dead Corners: Material accumulates in dead corners such as the screw, barrel, die inner wall, and the back of the filter plate, leading to prolonged heat decomposition.
Excessive Impurities: Impurities or degraded materials are mixed in. Ensure the raw materials are clean and strictly control the quality and proportion of recycled materials.
By systematically analyzing the root causes of problems and implementing targeted solutions, we can effectively improve the quality and stability of plastic pelletizing. If you're still struggling with various issues during the pelletizing process and can't produce satisfactory plastic pellets, KiTech's recycling and pelletizing equipment is the best solution. We have a professional technical team, a passionate sales team, and excellent after-sales service to ensure you receive the most satisfactory service both before and after the sale.
Plastic pellets produced using KiTech's recycling and pelletizing equipment exhibit the following excellent properties:
Size Uniformity: Highly consistent pellet size.
Color Uniformity: Pellets with uniform color distribution.
Appearance Excellent: Smooth surface, free of bubbles.
Standard Compliance: Fully meets all standards for recycled plastic manufacturing.
Please contact our team for an initial discussion. We are committed to producing the highest quality products at the most competitive prices.
Email: remond@kitechpm.com
Contact us: https://www.kitechrecycle.com/contact-us