In high-precision plastic assembly applications, process control and repeatability are everything. One feature that often gets overlooked – but can significantly enhance part quality and cycle consistency – is post cooling.
At Thermal Press International, our machines include an optional post cooling feature, designed to improve the consistency and durability of thermoplastic assemblies by introducing a brief burst of cooling air after the heat sealing or staking process.
What is Post Cooling?
The post cooling option enables programmable airflow to be directed at the part for a set amount of time immediately after the thermal cycle completes. Once the sealing or staking is finished, air is blown onto the part to cool the joint and surrounding material. This airflow can be applied while:
- The actuator remains down on the part (during dwell phase), or
- After the actuator lifts up and retracts (post-dwell phase)
This flexibility allows manufacturers to fine-tune the process depending on the application and material type.
Why Use Post Cooling?
Post cooling can provide measurable benefits in various manufacturing scenarios:
- Prevents Plastic Rebound
Certain plastic resins tend to “rebound” – attempting to return to their original shape once pressure is released, especially before the material has fully solidified. This can lead to loose or inconsistent staking results. Cooling the plastic ensures it reaches a solid state before force is removed, helping to lock the stake in place. This becomes even more critical when compressing a spring or other compliant material, as these can push the stake upward if pressure is released prematurely.
- Reduces cycle-to-cycle temperature variation
Cooling the part quickly after each cycle minimizes residual heat buildup, especially useful during long production runs.
- High Glass-Filled Resins require High Temperatures
Plastic resins with high percentages of glass filler typically require elevated staking temperature to ensure proper material flow and to avoid cracking or fracturing. However, the more heat that is applied, the more important it becomes to cool the plastic before retracting the staking probes. Cooling the plastic with a burst of air directed at the probe tip helps rapidly bring the temperature down after forming – protecting tooling and improving part consistency.
- Improves part dimensional stability
For precision assemblies where shrinkage or deformation can affect fit or function, controlled cooling helps parts maintain form.
- Enhances seal strength and reliability
By lowering the part’s temperature while it’s still under pressure, the bond can stabilize more consistently, reducing rework or failures.
- Ideal for metal-in-plastic assemblies
In assemblies where metal components are embedded into plastic, post cooling prevents heat transfer from warping or damaging adjoining areas.
When Should You Consider Post Cooling?
This option is particularly useful in:
- Medical device sealing with thin films or layered materials
- Assemblies using temperature-sensitive substrates
- High-volume production where process repeatability is critical
- Applications requiring post-process handling or inspection shortly after sealing
How It Works on Thermal Press International Machines
On applicable models, the post cooling feature is controlled through the touchscreen interface. Operators can:
- Turn the feature ON or OFF
- Set the cooling duration in seconds
- Choose when the cycle cooling should occur (while the actuator is engaged or after retraction)
This level of customization helps integrate post cooling seamlessly into a variety of thermal assembly workflows.
Interested in Post Colling for Your Application?
Post cooling is available as an optional feature on many of our heat staking and heat sealing systems. If you’re unsure whether it’s right for your process, our engineering team is happy to provide guidance.
Contact us at (925) 454-9800 or visit www.thermalpress.com to reach an expert about integrating post cooling into your assembly process.
