Heat Staking
Heat staking forms the projecting end of a thermoplastic post into a retaining head, capturing another component without requiring that component to melt or bond. It can be considered for joining molded housings to brackets, boards or dissimilar materials. The design needs enough plastic for a controlled head, stable support beneath the post and a clear retention requirement for the finished assembly.
The post is part of the fastening design
A stake should not be treated as an ordinary locating pin with an arbitrary amount left above the mating part. Its exposed volume and geometry must produce the required head without splitting, excessive thinning or unwanted displacement. The mating hole and available head clearance belong in the same design review.
Where the captured component is sensitive to clamping stress, define whether it should be held tightly or retained with controlled movement. A rigidly trapped component may respond differently to thermal expansion than a component allowed limited clearance.
Separate the three contact regions
| Region | Requirement to review |
|---|---|
| Post base | Support against forming force and resistance to local cracking |
| Mating component | Hole clearance, edge condition and acceptable contact stress |
| Formed head | Retaining area, height and clearance to nearby features |
Fixture support should locate the assembly without bending the substrate. For a board or thin bracket, uneven support can produce damage even when the stake head looks correct.
Establish a controlled forming cycle
Heating softens the post tip sufficiently for forming; tooling then shapes the retaining head under controlled conditions. The part must retain an acceptable shape when released. Excess heat or force may distort the surrounding wall, while insufficient forming may leave unreliable retention.
Review the actual resin grade and any filler. Approve samples by inspecting the head and surrounding material, then test retention under the relevant load and temperature conditions. Long-term load matters because thermoplastics can relax over time.
Buyer questions
Must both components be the same plastic?
No. The process mechanically captures the mating component; it does not require a fusion weld between the two materials.
Can a staked assembly be opened for repair?
It is usually a permanent connection. Removing the formed head can damage the post, so serviceability should be considered before selecting staking.
Is a larger head always stronger?
Not necessarily. Retention also depends on post integrity, the mating hole, support and the service load path.
Compare retention strategies before tooling
For threaded or repeated assembly, insert molding may offer a different design route. Coordinate post geometry through custom mold making and provide the mating-part drawing for a quotation.