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Liquid Silicone Rubber (LSR) Injection Molding Services

Design, validate, and manufacture custom silicone parts with stable, repeatable quality.

Dabojin supports you from early concept through production using Liquid Silicone Rubber (LSR) injection molding for parts that must stay flexible, seal reliably, and survive real-world conditions.

If the part is large, heavily loaded, or better suited to silicone compression molding or silicone extrusion, we will recommend that path rather than forcing everything into LSR.

Where LSR is the right tool

 
  • Flexible parts that must seal or cushion in real-world conditions
  • Membranes, living hinges, sealing lips, and fine details
  • Medical, food-contact, or demanding environmental exposure
  • Projects that need repeatable, stable elastomer properties
 

Why engineers choose LSR molding

Liquid Silicone Rubber is a two-part, platinum-cured silicone that is metered, mixed, and injected into a heated mold, then cross-linked into a stable elastomer. Properly specified LSR offers:

  • Excellent flexibility and tear strength - suitable for thin membranes, living hinges, sealing lips, and repeated flex.
  • Biocompatibility and purity - medical and food-grade materials available for direct-contact applications.
  • Stable properties over time - low compression set, good fatigue resistance, and consistent performance.
  • Ability to fill complex geometries - low viscosity supports fine features, undercuts (with appropriate tooling), and tight details.

At Dabojin, we use these properties to solve functional problems such as sealing, isolation, cushioning, and protection, not simply to make a silicone part.

 

What we make with LSR

We mold custom LSR components for small to medium-sized parts, including:

  • Seals and gaskets: radial, face, flange seals, O-ring alternatives.
  • Valves and membranes: check valves, duckbill valves, diaphragms, thin-film membranes.
  • Electrical and electronics: connector seals, cable boots, strain reliefs, keypads, switch boots.
  • Fluid handling: peristaltic pump segments, manifolds, hose interfaces.
  • Consumer and food-contact: soft-touch grips, baby and food-contact components (with proper material selection).
  • Overmolded elements: LSR over plastic or metal inserts for sealing, damping, or grip.
 

Design and engineering support, from sketch to mold-ready

Your project does not need finished CAD to start.

Define function

What must the part do: seal, cushion, protect? We clarify pressure, temperature, and media exposure so the design matches real operating conditions.

Clarify interfaces and constraints

Mating components, grooves, envelope, assembly method. We sort which dimensions are CTQs and which can float to avoid over-tolerancing and cost.

Convert to manufacturable geometry

We adapt geometry for LSR flow and cure: wall transitions, parting line and gate strategy that protects sealing surfaces and appearance, and demold strategy when draft is limited.

DFM before tooling

We flag risk areas such as air traps, knit lines, thin features, and unrealistic tolerances, then propose concrete fixes. You get specific comments, not “not manufacturable”.

Outcome: a design that works in your system and runs predictably in production.

Our LSR injection molding process

From first technical review to stable production, we use a structured process so you know what is happening at each stage.

1. Material and process selection

We match LSR grade and process to the application before tooling begins.

  • Durometer and modulus for function and assembly
  • Color or clarity and any optical requirements
  • Regulatory needs such as medical or food-contact
  • LSR alone vs. LSR overmolding onto plastic or metal

2. Tooling concept and quotation

We design a tooling concept that fits your volumes, budget, and risk profile.

  • Cavity count and layout based on forecast volumes
  • Clear split of tooling cost vs. piece price
  • Estimated cycle times and capacity options

3. Tool design and build

We build tools specifically for LSR behavior, not just adapted from thermoplastics.

  • 3D mold design with gating and venting for LSR flow
  • Thermal control and runner strategy set for cure consistency
  • Fixtures as needed for trimming or secondary operations

4. Sampling and FAI

We validate that the tool and process can deliver good parts before production release.

  • Trial runs to validate fill, cure, demold, and dimensions
  • First Article Inspection on agreed CTQs
  • Visual and functional checks on critical surfaces and features

5. Process locking and production

We fix a process window, then run to that window with defined checks.

  • Locked settings for injection profile and cure profile
  • In-process checks at defined intervals
  • Documentation of any approved parameter adjustments

6. Ongoing optimization

As field data and demand evolve, we adapt the process rather than leaving it static.

  • Feedback loop for field issues or engineering changes
  • Options to scale cavity count and capacity
  • Continuous improvement on scrap, cycle time, and consistency
 

Materials, durometers, and options

We source commercial LSRs from established suppliers.

  • Hardness: approximately 10 to 80 Shore A, depending on grade.
  • Colors: natural or translucent, optical transparency where appropriate, or custom pigments.

Special properties on request:

  • Medical and biocompatible grades for skin or short-term implant contact.
  • Food-contact compliant grades.
  • Oil and chemical-resistant formulations.
  • Self-adhesive LSR for bonding to selected plastics or metals during overmolding.

We will recommend a short list of candidates matched to your environment, mechanical needs, and regulatory constraints.

 

Tolerances and feature capability

Tolerances on LSR parts split by how the feature is formed, which is the distinction that matters and the one most quotes get wrong.

Fixed dimensions sit entirely within one mold plate. Nothing about mold closure affects them, so they hold tightest: ±0.05mm to ±0.15mm depending on size, which is ISO 3302-1 class M1 to M2.

Closure dimensions cross the parting line, so mold closure and flash variation both move them: ±0.10mm to ±0.30mm, class M2 to M3.

This is why “what tolerance can you hold” has no single answer until we have seen your drawing. During DFM we mark which of your dimensions are fixed and which are closure, and where a tight tolerance sits on a closure dimension we will tell you before tooling, not after first shots.

 

Quality and validation

Every silicone part supports a larger system. We can provide:

  • FAI with documented CTQ measurements.
  • Incoming and in-process checks on material, weight, and key dimensions at defined intervals.
  • Visual and functional inspection of sealing lips and optical areas.
  • Traceability to material batches and molding lots according to your risk profile.

When required, we align to your internal quality plan and IQ, OQ, PQ steps, and support PPAP-like documentation levels.

 

When LSR injection molding is the right choice

We recommend LSR when:

  • You need highly repeatable parts with complex features in small to medium geometries.
  • The application demands temperature performance, biocompatibility, or chemical resistance beyond common thermoplastics.
  • You require membranes, living hinges, fine seals, or mixed thin and thick sections in one part.
  • Volumes justify injection tooling and are scalable via multi-cavity molds.

For very large parts, simple profiles, or specific mechanical loads, we may propose compression molding, transfer molding, or extrusion.

 

What to include with your RFQ

Please share:

  • 3D model (STEP or IGES) and any 2D drawings and tolerances.
  • Estimated annual volumes and ramp-up plan.
  • Application and environment (media, temperature, pressure, contact type).
  • CTQs and performance targets (leak tightness, cycle life, optical clarity).
  • Regulatory and compliance needs (medical, food-contact, flammability, and similar constraints).
  • Preferences for color, transparency, and surface finish.

No CAD yet? We can start from sketches or sample parts and formalize the geometry.

 

Common questions about LSR injection molding

What parts suit LSR, and when should I use compression molding instead?

LSR suits thin membranes, living hinges, sealing lips, fine detail, and high-volume repeatable parts. Its low viscosity fills geometry that compression molding cannot.

Compression molding suits larger parts, heavier sections, short to medium runs, and lower tooling cost. If your part is large, heavily loaded, or better suited to silicone compression molding or silicone extrusion, we will quote that instead. We would rather lose the LSR job than sell you a process that fights your part.

What tolerances do you hold on LSR parts?

It depends on how the feature is formed. Fixed dimensions, contained within a single mold plate, hold ±0.05mm to ±0.15mm depending on size (ISO 3302-1 class M1 to M2). Closure dimensions, which cross the parting line, hold ±0.10mm to ±0.30mm (class M2 to M3). We mark which is which on your drawing during DFM.

What durometers can you run?

Shore A 10 to 80, depending on grade. Durometer is confirmed during DFM against sealing force, assembly method, and service conditions rather than picked from a chart.

Can you overmold LSR onto plastic or metal inserts?

Yes. LSR is overmolded onto plastic and metal inserts for sealing, damping, and grip. Substrate compatibility and bond geometry are checked before tooling. See silicone overmolding for substrate detail and how we prevent delamination.

What is the lead time?

Tooling runs 20 days, then first parts 1 to 2 days after that. All calendar days, not business days. DFM review comes back within 24 hours on weekdays.

Do you have a minimum order quantity?

No MOQ. Tooling cost is quoted against your part after DFM rather than from a price list, because cavity count and part complexity move the number more than anything a starting price would tell you.

What do you need to quote?

A STEP, IGES or DWG file, or a PDF drawing with key dimensions. Tell us the service temperature, what the part seals or contacts, and any compliance requirement such as food contact or ISO 10993. We are ISO 9001, ISO 14001 and ISO 45001 certified, and we will confirm the material grade against your application before quoting.

 

Ready to discuss an LSR project?

Whether you are evaluating LSR or replacing an existing silicone component, Dabojin can help you:

  • Clarify functional requirements,
  • Choose the right silicone and process, and
  • Move from concept to stable, repeatable production.

Share your project details. We will respond with practical feedback, realistic options, and a path to a manufacturable design, not just a number at the bottom of an email.

Share your project details

 

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