Using Controlled Heating and Cooling to Seal a Small Polycarbonate Port
Case study · Impulse heat staking
By Alex Spurgeon — Published 2026-09-21
A customer needed to permanently seal a 1–2 mm port in a thin-walled polycarbonate part. Their continuously heated probe formed the seal, then pulled it apart, because softened plastic stuck to the hot tool on retraction. U.S. Heatstake's impulse heat staking heats the tool, forms the seal, then cools the tool while it is still in contact, so it retracts only after the plastic has solidified.
At a glance
| Application | Permanently sealing a port approximately 1–2 mm in diameter |
|---|---|
| Material | Thin-walled polycarbonate |
| Previous process | Continuously heated probe |
| Problem | Softened plastic stuck to the hot probe and pulled away from the part on retraction |
| Solution | Impulse heat staking with independently controlled heating and cooling |
| Outcome | Consistent, repeatable seals with no material pullback and less scrap |
The challenge: the seal formed, then pulled apart
A customer needed to permanently seal a very small port in a thin-walled polycarbonate component. The opening was only approximately 1–2 mm in diameter, leaving very little room for process variation.
Their existing process used a continuously heated probe.
The probe could melt and form the polycarbonate over the opening, but it created another problem: because the tooling remained hot during retraction, softened plastic would stick to the probe and pull away from the part.
The seal would form—and then be pulled apart as the tool retracted.
The solution: cool the tool before it lets go
U.S. Heatstake's impulse technology allowed the heating and cooling portions of the process to be independently controlled.
The tool could lightly contact the small feature and apply only the heat necessary to form the seal. Once the material had flowed into the desired shape, the system actively cooled the tooling while it remained in contact with the part.
Only after the polycarbonate had solidified did the tooling retract.
- Contact: cold tool lightly touches the port.
- Heat: only the heat needed to flow the polycarbonate.
- Cool in contact: tool is actively cooled while it holds the shape.
- Retract: tool releases after the plastic has solidified.
The results
- Successfully sealed a delicate 1–2 mm polycarbonate port
- Eliminated material pullback during tool retraction
- Allowed the plastic to solidify before tooling release
- Produced consistent, repeatable seals
- Reduced scrap caused by failed seals
- Provided precise control for a thin-walled, delicate component
- Enabled an application that continuously heated tooling could not reliably perform
In this application, heating the plastic was only half of the process. Controlling when the tooling cooled and released the material was what made a reliable seal possible.
Common questions
Why does plastic stick to a hot probe and pull away during heat staking?
A continuously heated probe is still hot when it retracts, so the plastic under it is still soft. The softened material sticks to the tool and is pulled away from the part. The fix is to cool the tooling while it is still in contact and retract only after the plastic has solidified, which is how impulse heat staking works.
How do you seal a very small hole in a thin-walled polycarbonate part?
Apply only the heat needed to flow the material over the opening, then cool the tool in place before releasing it. In this application U.S. Heatstake used impulse tooling with independently controlled heating and cooling to seal a 1–2 mm polycarbonate port consistently, without material pullback.