Sep 6, 2026Project Planning
Who Owns a Custom Silicone Mold? And How to Design Reliable Silicone Sealing Features
Two questions come up repeatedly in custom silicone projects: who owns the mold, and how do we make sure the molded seal actually works? Both are best resolved before tooling...
Two questions come up repeatedly in custom silicone projects: who owns the mold, and how do we make sure the molded seal actually works? Both are best resolved before tooling begins.
Part 1: Mold ownership
Before tooling starts, the quotation or tooling agreement should define who pays for the mold, who owns it, where it is stored, who is responsible for maintenance, whether modifications are included and whether the mold can be transferred.
What happens after the first sample?
It is normal for a custom mold to require adjustment after the first trial. The agreement should clarify which changes are included and which design changes require a new quotation.
Part 2: Reliable silicone sealing features
A molded seal is not reliable simply because it is made from silicone. Sealing performance depends on compression, geometry, hardness, surface contact, tolerance and shut-off quality.
Compression
The seal needs enough compression to close the leakage path without being over-compressed.
Groove geometry
The groove should support the seal and prevent rolling or extrusion.
Material hardness
Hardness affects how easily the seal conforms to the mating surface.
Tolerance stack-up
A good seal design must account for both the silicone part and the rigid housing.
Overmolded seals
For silicone molded directly onto plastic or metal, bonding and edge geometry are also critical. A seal may fail if the bond edge lifts or the insert deforms.
Review tooling and sealing together
The mold design determines flash, venting, local dimensions and repeatability. Sealing features should be reviewed during DFM, not after a failed water test.
Need a custom silicone mold or sealing feature reviewed before tooling? Send your CAD for DFM feedback.
