Sep 20, 2026Silicone Guides
Plastic + Silicone Tooling Checklist
Review wall thickness, undercuts, draft, venting, substrate stress, material compatibility and assembly before tooling a plastic + silicone product.
The most expensive tooling correction is usually the one discovered after the mold is finished.
For plastic + silicone and other multi-material products, a pre-tooling review should look beyond whether the CAD model is visually complete. The design also has to be fillable, demoldable, stable, compatible with the rigid substrate, and able to assemble correctly.
1. Silicone Wall Thickness
Is the silicone area thick enough to fill consistently? Very thin sections can create incomplete filling, unstable appearance, weak local geometry and higher sensitivity to process variation.
2. Undercuts
Deep undercuts may make demolding difficult or damage the molded part during release. The question is not only whether the shape can be drawn. It is whether the shape can be produced repeatedly.
3. Draft Angle
Insufficient draft can increase demolding force, deformation, surface damage and cycle instability. Draft should be reviewed before the steel is cut.
4. Venting
Air has to leave the cavity as material enters. Poor venting may contribute to trapped air, bubbles, incomplete filling, surface issues and unstable process conditions.
5. Plastic Substrate Stress
The rigid substrate also has to survive the silicone molding process. Some plastic structures may whiten, crack or deform when exposed to the wrong combination of temperature, pressure, molded-in stress and geometry.
6. Material Compatibility
Silicone and plastic should be reviewed as one product system. Questions include: Is direct bonding required? Is mechanical retention used? Can the plastic tolerate the process temperature? Will the interface remain stable during use?
7. Insert Positioning
If a plastic component is placed into the silicone mold, its position must stay controlled during molding. Poor insert positioning can affect silicone thickness, edge definition, dimensions and assembly.
8. Assembly Tolerance
Even if both molded components pass individual inspection, the final assembly can still fail because of tolerance stack-up. Critical interfaces should be reviewed as part of the finished product.
Good Tooling Starts With Good DFM
Changing a wall, radius, undercut or draft angle in CAD is relatively easy. Changing the same issue after tooling has started is a different conversation.
Related Pages & Case Studies
· Silicone + Plastic Components - /silicone-plastic-components
· Silicone Overmolding - /silicone-overmolding
· OEM & ODM Product Development - /product-development
· Case study: Avoiding Tooling Rework With a Pre-Mold DFM Review - /case-study-lsr-overmolding-dfm-before-tooling
Planning a Plastic + Silicone Product?
Send the 3D drawing, substrate material and assembly requirement before tooling. We can review the major moldability and interface risks first.
Request a DFM Review - /contact-us#project-inquiry
