Liquid Silicone Rubber Overmolding Service
Fecision bonds LSR to a rigid substrate to create a seal or soft contact surface within one assembly. We review the material pair and bonding method before developing the tooling and validation plan.
- ISO 9001 Certified
- ISO 13485 Certified
- Tolerances tight to +/- 0.02 mm
LSR Overmolding Services Built For Production
Fecision overmolds liquid silicone rubber onto plastic and metal substrates, creating non-slip grips for medical devices, waterproof seals for electronics, and parts that withstand extreme temperatures. With control over silicone rubber grade, color, and hardness from 10 to 80 Shore A, we take your project from prototype to mass production with confidence.
Combining the materials in one molded part can reduce separate bonding and assembly work. Fecision has already delivered millions of overmolded parts to clients around the world, and we would be glad to put that experience to work on your next project.
LSR Overmolding Materials
Match the LSR and substrate system before tooling begins. We review silicone grades, engineered plastics, metals, and surface requirements to improve bonding strength and long-term assembly performance.
LSR + Engineering Plastics
For lightweight, insulated, or temperature-precision components, silicone can overmold rigid plastics to create sealed, functional assemblies.
LSR + Metal
Good combinations of high-strength structural support and flexible sealing. Ideal for inserts, threaded hardware, and electrical connectors.
Fecision works with established silicone suppliers, including Wacker, Dow, Momentive, and Shin-Etsu. For custom formulations, we first establish the bond required with the substrate. The material is then developed to meet the part's service conditions and molding requirements.
LSR Overmolding Capabilities
Read our overmolding capabilities to help you review part size, tolerance, substrate options for sealed, bonded silicone rubber assemblies.
| Standard | Description |
|---|---|
| Size | 300 x 200 x 100 mm |
| Tolerance | Mold tolerance: +/- 0.01 mm, Parts tolerance: +/- 0.05 mm |
| Part to Part Repeatability | +/- 0.1 mm |
| Mold Cavities | Single cavity molds, multi-cavity molds |
| Mold Cavity Life | 3 million to 5 million shots for production tooling |
| Mold Material | Tool steel: P20, H13 Stainless steel: 420 |
| Available Mold Types | Prototype tooling, production tooling |
Secondary Operations
Secondary operations keep overmolded silicone rubber rubber assemblies production-ready.
LSR Overmolding Case Studies
See how Fecision helps customers move LSR overmolded parts from validation to repeatable production.
"The challenge was not only bonding silicone rubber to a transparent PC mask. The part needed a clean, soft seal with no flash, no trimming, and no scratches on the optical surface."
Zero-Flash LSR Overmolding on a Transparent Respirator Mask
A respiratory device manufacturer needed a transparent PC mask with an overmolded LSR seal. Any silicone flash or post-mold trimming could damage the clear surface and turn the part into scrap.
Fecision supported the project with overmolding DFM review, precision tooling control, and process validation to produce a clean soft seal straight from the mold.
Full Case StudyGlance At LSR Overmolded Products Fecision Made
Explore overmolded parts that combine a rigid structure with a functional silicone surface.
LSR Overmolding Processes
LSR overmolding depends on insert preparation, tooling control, and stable bonding between silicone rubber and substrate.
DFM Analysis
Review your drawings, material requirements, and application needs. Complete DFM analysis and confirm tooling, tolerance, and production specifications before manufacturing begins.
How Does LSR Overmolding Work?
LSR overmolding works by placing a thermoplastic or metal part into a heated mold, then injecting liquid silicone rubber (LSR) over it so the LSR flows, encapsulates, and chemically cross-links onto the substrate surface during the cure cycle. As the LSR vulcanizes at high temperature, it forms a permanent bond through a combination of molecular adhesion and mechanical interlocking, then produces a single integrated component.
This process combines the best of both materials, the structural strength of the plastic substrate and the softness, sealing capability, and vibration-damping performance of silicone rubber.
LSR Overmolding Design Guidelines
Good overmolding design improves bonding, insert placement, silicone flow, demolding, and inspection. Use these rules before finalizing the substrate and mold plan.
| Design Rules | Guidelines |
|---|---|
| Wall Thickness | Keep uniform at 0.5-10 mm, minimum 0.5 mm, maximum 6.0 mm. |
| Draft Angle | Apply 0.5-3 degrees for automated demolding and textured surfaces. |
| Corner Radius | Inside radius should be 0.5 mm; outside radius around 1.5 mm. |
| Undercuts & Parting Line | Use split molds, slides, or lifters only when the design requires them. |
| Shrinkage & Tolerance | Compensate for 2.5-3.5% silicone shrinkage during mold design. |
Applications Of LSR Overmolding Product
LSR overmolding is a strong fit for products that need integrated seals, insulation, vibration damping, or bonded silicone-to-substrate performance.
Consumer Electronics
Soft-touch components designed around product use and operating environment.
Consumer ElectronicsBaby Care
Pacifiers, bottle nipples, teething toys, and durable safe silicone rubber parts.
Food & Baby CareAutomotive
Connector seals, vibration components, grommets, and protective silicone rubber parts.
Mobility SolutionsElectronics
Waterproof seals, protective casings, keypad interfaces, and soft gaskets.
Electronics SolutionsFrequently Asked Questions
These answers cover common LSR overmolding questions around substrate choice, adhesion, tooling, sampling, and production validation.
What materials can you mold?
We work with food-grade LSR, medical-grade LSR, optical-grade silicone, fluorosilicone, and custom compounds selected for each product requirement.
Can you support low-volume validation before mass production?
Yes. We can begin with DFM review, prototype tooling, and validation runs before moving into multi-cavity production tooling.
Do you provide secondary operations?
Yes. We can finish and assemble molded parts in-house. The required operations, such as post-curing or printing, are agreed during project review before final inspection and packaging.
Ready to build LSR Overmolding parts?
Send drawings, substrate details, target silicone grade, and volume. We will review the bonding route and return practical production feedback.