Today's KNOWLEDGE Share The Critical Role of Pre-Drying in Injection Molding

Today's KNOWLEDGE Share

The Critical Role of Pre-Drying in Injection Molding

Bubbles, silver streaks, weak parts? Often, it’s due to one thing: wet material.

🔍 Why dry?

Plastics like Nylon (PA), PC, and PET absorb moisture from air. When processed, this moisture turns to steam—causing defects, weaker properties, and even part failure. Even hydrophobic materials (e.g., PP, PE) can benefit from drying for better appearance and consistency.

With more regrind materials (often wetter) and stricter regulations, drying is becoming essential.

🌬️ How to dry?

Hot Air Drying: Good for hydrophobic materials such as PP, PE. Simple, low-cost.

Desiccant Drying: The best choice for hygroscopic materials and a must for hydrolyzable types like PA, PC, and PET. It's highly efficient in humid conditions.

📊 Key parameters:

Temperature

Drying time

Airflow

Dew point

✅ Best Practices:

Store material sealed & dry

Avoid over-drying

Check moisture with analyzers

Monitor dryer performance & dew point

Bottom line: Pre-drying isn’t optional—it’s critical for quality. Smart molders don’t guess; they measure and control moisture.

How do you handle material drying in your process? Share below.

source : Kevin Zou