Screw barrel Immobilization in Nylon 6 Injection Molding: A Comprehensive Analysis and Solutions

Nylon 6, a versatile engineering plastic with exceptional properties, finds extensive applications across industries such as automotive, electronics, electrical, and textiles. However, during the injection molding process of Nylon 6, a common challenge encountered is screw barrel immobilization, hindering material feeding and disrupting production.

Nylon 6, characterized by its high melting point, low melt flow, and high viscosity, exhibits certain inherent properties that can contribute to screw barrel immobilization during injection molding:

Inadequate Material Temperature: Nylon 6 requires a recommended melt temperature range of 220-290°C. If the material temperature falls below this range, the viscosity increases significantly, impeding melt flow and generating excessive resistance, leading to screw barrel immobilization.

Low Mold Temperature: Nylon 6 possesses a high degree of crystallinity. When mold temperatures are too low, the material tends to solidify prematurely within the mold cavity, increasing ejection resistance and causing screw barrel immobilization.

Excessive screw barrel Backpressure: screw barrel backpressure refers to the counteracting force exerted by the molten plastic against the screw barrel threads. Overly high backpressure substantially increases the rotational resistance on the screw barrel, potentially leading to immobilization.

Improper Injection Parameters: Inappropriate settings for injection parameters, including injection pressure, injection speed, and holding time, can also contribute to screw barrel immobilization.

Mechanical Malfunctions: Underlying mechanical issues, such as hydraulic system failures, motor malfunctions, or transmission system defects, can also hinder screw barrel rotation.

Material Moisture: Nylon 6, being a hygroscopic material, readily absorbs moisture from the surrounding environment. If this moisture is not effectively removed prior to processing, it can increase melt viscosity, promote hydrolysis and degradation, lead to premature solidification, and cause voids and defects.

Implementing Effective Solutions

To effectively combat screw barrel immobilization during Nylon 6 injection molding, the following remedial measures are recommended:

Use nylon 6 special screw.

Elevate Material Temperature: Within the permissible range that prevents material degradation, gradually increase the material temperature to reduce melt viscosity, enhance flowability, and minimize screw barrel resistance.

Increase Mold Temperature: Raise the mold temperature to slow down material solidification within the mold cavity, diminish ejection resistance, and facilitate melt filling.

Adjust screw barrel Backpressure: Strategically lower the screw barrel backpressure to alleviate rotational resistance on the screw barrel and prevent immobilization.

Optimize Injection Parameters: Carefully adjust injection pressure, injection speed, and holding time to align with the specific requirements of Nylon 6 injection molding.

The sol time needs to be long enough, including the screw retreat speed and pressure setting.

Conduct Mechanical Maintenance: Regularly inspect and maintain mechanical components, including the hydraulic system, motor, and transmission system, to ensure their optimal performance.

Thorough Material Drying: Subject Nylon 6 granules to a thorough drying cycle using desiccant dryers or hopper dryers to reduce moisture content to less than 0.1%.

Embracing Preventive Measures

To proactively prevent screw barrel immobilization during Nylon 6 injection molding, the following preventive measures should be implemented:

Material Selection: Carefully select the appropriate Nylon 6 grade and additives based on specific product requirements.

Effective Drying Process: Due to its hygroscopic nature, Nylon 6 necessitates thorough drying prior to injection molding to minimize moisture content.

Optimal Mold Design: Consider Nylon 6's shrinkage rate and melt flow characteristics when designing the mold, avoiding excessive wall thickness variations, sharp corners, and acute angles.

Standardized Operating Procedures: Establish and strictly adhere to standardized operating procedures to ensure consistent and correct operation by personnel.

Regular Maintenance: Implement a regular maintenance schedule for the injection molding machine to maintain its overall functionality.

By implementing these comprehensive measures, injection molders can effectively prevent screw barrel immobilization during Nylon 6 processing, ensuring uninterrupted production and consistently high-quality products.

Barrelize focus on manufacturing type of screw and barrel for injection molding and extrusion machine.