Silicone (LSR) Overmolding & Insert Molding
We provide one-stop service from mold design and DFM through tooling and silicone molding, delivering production-ready overmolded and insert-molded components.
LSR Overmolding & Insert Molding Solutions
We combine liquid silicone rubber (LSR) with metal, plastic, and electronic components to create sealed, soft-touch, and durable parts. You provide the part and insert designs; we handle DFM, mold design, tooling, and molding to deliver finished LSR components ready for assembly.
LSR Overmolding
LSR overmolding adds a molded liquid silicone rubber layer onto an existing plastic or metal part. The rigid substrate provides structure and precision; the LSR layer brings sealing, softness, and impact protection in a single operation.
We typically use LSR overmolding when you need to:
Create soft-touch grips and ergonomic surfaces on handles, tools, and device housings
Integrate silicone seals, lips, and barriers directly onto rigid components
Add cushioning or shock absorption around sensitive areas or edges
Improve slip resistance and comfort on user-contact surfaces
You share your substrate design and performance targets; we optimize the LSR overmold geometry, design the mold, and deliver production-ready parts.
LSR Insert Molding
LSR insert molding encapsulates pre-placed inserts – such as metal parts, engineering plastic carriers, or small electronic components – with liquid silicone rubber inside the mold. The insert provides strength, precision, or function, while the LSR adds sealing, cushioning, and biocompatible or soft-touch surfaces in one integrated part.
We typically use LSR insert molding when you need to:
Combine metal or plastic cores with a bonded silicone outer layer for strength and comfort
Mold seals, gaskets, and barriers directly around precision inserts and interfaces
Protect sensors, contacts, or small PCBs inside a flexible, shock-absorbing silicone body
Replace multi-part assemblies and manual bonding with one molded composite component
You provide the insert design and requirements; we design the LSR tooling, define the process, and deliver ready-to-use insert-molded silicone parts.
Kemal LSR Overmolding & Insert Molding Capabilities
| Capabilities | Details |
|---|---|
|
Supported part types |
Soft-touch grips and handles, seals and gaskets on rigid parts, medical and handheld device components, protected electronic modules and sensors |
|
Substrate / insert materials |
Engineering plastics (PC, PA, PBT, PPS, etc.), stainless steel and aluminum inserts, stamped or machined metal parts, small PCBs and electronic inserts |
|
LSR grades |
General-purpose and high-performance LSRs, including medical-grade, food-contact and high-temperature formulations, selected to match your application |
|
Typical part size & complexity |
From small buttons and seals to medium-size grips, housings and multi-insert assemblies with localized overmolded features |
|
Volume range |
Prototype and pilot batches through ongoing series production, with the same engineering team supporting each stage |
|
Production scale |
Prototype runs, pilot builds, and full mass production with documented process windows |
|
Quality & testing options |
Visual and dimensional checks on critical LSR features, bonding evaluation, pull and leak testing, and application-specific validation on request |
Why Choose Kemal for LSR Overmolding & Insert Molding
Predictable Lead Times
Mold design, toolmaking, and LSR overmolding/insert molding are handled in-house, so your schedule is not exposed to subcontractor delays. With dedicated LSR injection and metering systems, controlled mold-temperature support, and planned production slots, we run a clear milestone flow from free DFM to T0 trials and sample approval. Progress updates can be shared during the project to support internal planning and customer review.
Free DFM Report
We provide a free DFM and seal-design review before cutting steel, based on your 2D/3D data, inserts, and target sealing requirements. Our engineering team checks shut-offs, parting lines, venting, and critical bond/seal areas up front, then returns clear recommendations and options to reduce trial loops and avoidable tool rework. If needed for evaluation, we can share redacted DFM samples and introduce the design team supporting your project.
ISO Quality System
We operate under an ISO 9001 quality management system and run LSR overmolding/insert molding with defined inspection and release criteria. Key characteristics and common defects are checked against a controlled process window, with records linked to lots to support repeatable production and fast issue isolation. The ISO 9001 certificate and selected redacted, audit-ready record samples. For regulated medical programs, ISO 13485 support can be available when applicable.
Insert Positioning & Fixturing Control
We use dedicated fixtures to locate inserts accurately and keep them stable during LSR overmolding, reducing shift, float, and damage risks. Critical datums, shut-offs, and contact areas are confirmed before trials to improve first-shot success and repeatability in production. Fixture shop-floor photos and redacted CAD/fixture snapshots can be shared upon request for customer review.
Transparent Pricing & Change Control
We break down quotations clearly—tooling/fixtures, sampling and trials, materials, and production pricing—so you know what is included from the start. Any drawing, tooling, material, or key process changes are managed through a documented ECN/ECR workflow and confirmed before implementation, preventing surprise add-ons and version confusion mid-project. Redacted quote templates, ECN/ECR samples, and WhatsApp customer feedback on transparency can be shared upon request for customer review.
Sealing-First Tool Design
We design LSR overmolding tools around sealing performance first. Shut-offs, parting lines, venting, and seal/bond areas are optimized before tooling to reduce flash, trapped air, and leak risk. When contamination control is required, we can support controlled assembly and pack-out after molding. Shop-floor inspection/testing visuals and redacted leak/IP or dimensional check samples can be provided upon request for customer review.
Comprehensive Plastic Part Services
We review shut-offs, parting lines, venting, and bonding risks early to prevent flash and delamination. Insert locating and keep-out zones are confirmed before tooling to keep results stable from sampling to production.
Our molds are built with overmolding-specific shut-offs, venting, and insert fixturing to control flash at the interface. Tool design decisions are tied to your CTQs—sealing edges, cosmetic zones, and retention features.
Overmolding adds sealing, soft-touch grip, insulation, and protection directly onto plastic or metal substrates. We support bonding strategy and interface control so overmolded features perform reliably in production use.
Insert molding is the right route when parts must be encapsulated or mechanically retained inside the molded material. We focus on insert positioning, anti-float control, and CTQ-based inspection to keep inserts stable across cavities and lots.
We provide production-ready inspection and documentation, including FAI, dimensional reports, and material certificates by lot. For sealing or adhesion-critical projects, leak testing and interface validation can be defined during quoting.
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FAQ's
What’s the difference between silicone overmolding and LSR overmolding?
In practice, they’re often the same. “Silicone overmolding” is the general term, and “LSR overmolding” means we’re using liquid silicone rubber (LSR). Most production silicone overmolding we run is LSR injection molding because it’s more stable, repeatable, and easier to control flash and sealing performance.
Silicone overmolding vs silicone insert molding: which should I choose?
Choose silicone overmolding if you already have a rigid part (plastic/metal) and only need silicone on specific areas—like a seal lip, grip zone, edge protection, or strain relief.
Choose silicone insert molding if the insert needs to be placed into the mold and encapsulated or locked in as part of the structure (often for retention, precise positioning, or full protection).
If you share your CAD, substrate material, and sealing/bonding target, we’ll recommend the best route based on adhesion risk, shutoff/flash control, and tooling cost.
How do you prevent delamination between LSR and plastic/metal substrates?
We prevent delamination by treating it as a design + surface + process control issue, not just a material choice:
Confirm compatibility early: we select LSR grade and substrate (or coating) that are known to bond, and we confirm whether you need chemical bonding or mechanical locking.
Design for retention: we add grooves, undercuts, holes, or wrap features so the silicone is mechanically anchored even if chemical bond varies.
Control the surface condition: we avoid contamination (mold release, oils), and use primer or plasma/activation when bonding strength is critical.
Tooling shutoffs and venting: stable shutoffs reduce flash and keep the interface clean; venting prevents trapped air at the bond line.
Process window control: we lock key parameters (injection, cure, mold temperature) to keep cure and wetting consistent.
Verify with a defined test: if adhesion is a CTQ, we run pull/peel tests on coupons or sample parts and keep records for approval.
If you tell us the substrate material (e.g., PC/PA/PBT, anodized aluminum, stainless) and the environment (temperature, fluids), we’ll specify the bonding route and the validation method up front.
Can silicone overmolding achieve IP67/IP68 sealing? How is it verified?
Yes—silicone overmolding with LSR is commonly used to achieve IP67 or IP68 sealing when the gasket geometry, compression, and interface tolerances are designed correctly. We focus on seal lip design, controlled compression, and stable bonding to prevent leak paths.
Verification is done per the project requirement and typically includes:
Leak testing such as air-decay or pressure testing during sampling or pilot runs
Water immersion testing to the specified depth and duration
Dimensional inspection of seal-critical features and compression zones
Process stability checks to ensure sealing performance is repeatable in production
If IP rating is a CTQ, we define the test method and acceptance criteria before tooling and include the records with first-article or validation samples.
What substrate materials work best for LSR overmolding (PC/PA/PBT/metal)?
The “best” substrate is the one that gives you a stable interface with the bonding method you need (chemical bond, mechanical lock, or both). In production, these are the most common and reliable choices:
PC / PC-ABS: Often a strong option for housings and sealing interfaces. Good dimensional stability; bonding performance depends on resin grade and surface condition.
PA (Nylon, PA6/PA66): Works well for structural parts, but bonding can vary with glass-filled grades, moisture, and additives—mechanical locking features are commonly used to de-risk adhesion.
PBT: Frequently used for connectors/electronics. Can be a good substrate for LSR overmolding, but bonding is highly grade-dependent (especially FR or glass-filled), so we usually confirm the bonding route early.
Metal (stainless / aluminum): Very common for rugged sealing and handles. Chemical bonding typically needs surface prep (cleaning + primer/plasma), and we often design mechanical retention (holes/knurl/undercuts) for long-term reliability.
What we need from you to confirm the best match: the exact resin grade (and GF/FR content), any coatings (paint/anodize), surface finish/cleanliness requirements, and whether adhesion is a CTQ or a mechanical lock is acceptable.
How do you control flash on LSR parting lines and shut-offs?
For LSR, flash control is mainly a tooling shut-off and venting discipline. We control it with:
Shut-off-first design: we place parting lines away from cosmetic or seal-critical areas, and build firm shut-offs with proper land width and support.
Tight shut-off fit & rigidity: we control steel conditions on shut-offs and avoid “floating” inserts that open up under injection pressure.
Venting strategy: we vent where air traps occur so pressure doesn’t force silicone into micro-gaps along shut-offs.
Gate location and flow direction: we orient flow to reduce direct impingement on shut-offs and minimize pressure spikes at the parting line.
Stable process window: we lock injection/cure parameters and mold temperature to prevent over-pressurization that can create flash.
First-article flash criteria: we define acceptable flash limits up front and confirm them on sampling with photos/inspection notes.
If the part has a seal lip or touch surface, we treat those edges as CTQs and design the shut-offs specifically around them to keep trimming and rework out of production.
Can you support both prototype/pilot builds and mass production for LSR overmolding?
Yes. We support LSR overmolding from prototype and pilot builds through stable mass production. Early builds use production-intent materials and bonding methods so results carry over to scale. Tooling, shut-offs, and process windows are planned upfront to avoid rework when volumes increase, and we maintain the same validation, inspection, and change-control approach as programs move into production.
What information do you need to quote a silicone overmolding project?
To quote silicone overmolding accurately, we typically need:
3D CAD (STEP/IGES) and, if available, a 2D drawing with CTQ dimensions
Substrate material details (PC/PA/PBT/metal), including grade, GF/FR, and any coating (paint/anodize)
Overmold requirements: sealing (IP target), soft-touch/grip, insulation, strain relief, etc.
Bonding expectation: chemical bond required or mechanical locking acceptable
Cosmetic requirements: color, texture, parting line limits, flash limit, visible surfaces
Insert details (if any): material, tolerances, and how the insert is supplied/positioned
Quantity and ramp plan: prototype/pilot volume, annual volume, and target lead time
Validation/documentation needs: leak test, pull/peel test, FAI/dimensional report, material certs, traceability
If you share CAD plus the substrate material grade and your sealing/bonding target, we can usually confirm the tooling approach and quote scope quickly.
What inspection and documents can you provide (FAI, dimensional report, material certs, leak test)?
For silicone overmolding and LSR overmolding projects, we can provide inspection and documentation aligned to your CTQs, including:
First Article Inspection (FAI) with agreed critical dimensions and features
Dimensional inspection reports (CMM or fixture-based, depending on geometry)
Material certificates (COA/COC) for LSR and substrate materials, by lot
Leak test records (air decay, pressure, or water immersion) when sealing or IP rating is required
Visual and cosmetic inspection criteria for flash, parting lines, and surface condition
Lot traceability documentation for production runs
Process and change control records (ECR/ECN) when revisions are made
Documentation scope is defined during quoting so inspection and validation match the application, not generic paperwork.
Get a Quote for Silicone Overmolding (LSR)
Share your CAD and substrate material. We’ll confirm bonding approach, flash-risk shutoffs, and sealing targets before tooling.
