Ensuring Optimal Resin Dryness for High-Quality Injection Molding

Attention to Detail: Drying Isn’t Finished Until It’s Verified

Drying time alone doesn’t guarantee a material is ready for processing. Moisture levels can vary due to airflow, temperature, pellet size, or even how long the material sat exposed before loading.

Measurement confirms whether the resin actually meets the required moisture threshold before molding begins.

Why Moisture Measurement Is Necessary

Drying systems can drift without obvious signs. Airflow changes, dew point fluctuations, or inconsistent residence time can all affect performance.

Testing ensures the dryer is working correctly, the material hasn’t reabsorbed moisture, and each batch meets specification before entering the machine.

Typical Moisture Limits by Material

Different resins have different tolerance levels.

Polycarbonate, PBT, PET, and high-performance resins often require moisture levels below 0.02%. Nylon allows slightly higher levels, but still requires control to avoid defects. ABS blends fall in between.

Exceeding these limits leads to issues like brittleness, splay, haze, or inconsistent flow behavior.

Common Measurement Methods

Karl Fischer Titration

This is the most precise method available. It measures moisture chemically, detecting even very small amounts within the material.

It’s typically used in lab settings for validation, material qualification, and troubleshooting. The tradeoff is time and equipment complexity.

Infrared Moisture Analyzers

These are widely used on the production floor.

A sample is weighed, heated, and measured for weight loss. That loss is used to estimate moisture content. While slightly less precise than Karl Fischer, it’s fast and practical for routine checks.

This makes it the go-to method for verifying resin condition before processing.

Online Moisture and Dew Point Sensors

These systems monitor drying conditions in real time, often through dew point measurement.

They help maintain consistent drying performance and alert operators if conditions drift. Since they measure air conditions rather than the resin directly, they’re typically paired with periodic material testing.

How Moisture Testing Fits Into the Process

A consistent workflow keeps material condition under control.

After drying, a sample is taken from the hopper and tested using an infrared analyzer. The result is compared to the material’s specification. If it meets the requirement, the resin is transferred to the machine under controlled conditions.

If not, it returns to the dryer until it reaches the correct level.

What Happens Without Verification

Skipping measurement introduces uncertainty into the process.

Moisture-related issues can appear as surface defects, inconsistent filling, or reduced mechanical strength. These problems often require troubleshooting at the machine, even though the root cause starts with the material.

Catching moisture issues early prevents that cycle.

The Aprios Approach

Moisture verification is built into the process, not treated as an optional check.

Each material has defined limits, and every batch is tested before use. Results are recorded and linked to production data, creating traceability from raw material through finished part.

That control ensures the material enters the process in a consistent state, supporting stable molding conditions and repeatable part quality.