Liquid Silicone Rubber Molding — Engelhardt LSR Injection Services

Engelhardt provides liquid silicone rubber molding services to those customers that require close tolerances, excellent quality, high capacity from only one source. Our 150-ton LSR injection press dedicated in-house cold runner technology and mold shop machining capabilities produce flash-free component at a dimensional accuracy of 0.025mm with leading quality guarantee, ISO 9001 and IATF 16949 accreditation that below 5% of silicone manufacturers in China could have.

Trusted by Kohler · American Standard · Amphenol · Oatey · SFA

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150T

Dedicated LSR Press

2200×1200mm

Max Mold Size

ISO + IATF

Dual Certified

1000+ tons

Annual Capacity

30-50 days

New Mold Lead Time

±0.025mm

Achievable Tolerance

LSR Injection Molding Challenges — How Engelhardt Solves Them

Liquid silicone rubber (LSR) is a two-component, peroxide and cobalt-cured, thermoset elastomer which exhibits excellent low viscosity that ease the process for precision, injection molding of highly complex shapes and geometries. This unique characteristics of the LSR fluid, unlike the high consistency rubber or compression-molded silicone, which easily flows into long, thin-wall sections and down narrow mold cavi-ties without excess flash. However, this benefits only if your foundry control the whole supply chain-meter-ing, tooling, curing and part inspection-under one roof.

01 Challenge 1: Tight Tolerances Demand Specialized LSR Equipment

Standard squeeze and injection moulding machines are not able to hold the 0.025mm tolerances that precision LSR parts demand. Liquid Silicone Rubber (50,000-500,000 mPas fluid viscosity) is so low viscous, that any imbalance in the metering system or temperature deviation greater than 2 C will create flash, short shots or dimensional drift. We operate dedicated 150T LSR presses with a specific 2 components metering unit and static mixer set to 1:1 ratio accuracy. Our mold shop construct cold runner system to prevent material wastage and to achieve cavity-to-cavity repeatability across 64 mold cavities.

02 Challenge 2: Material Selection Confusion Leads to Wrong Process Decisions

How often do engineers call out HCR (high consistency rubber) in processes that require the installation of LSR- or that could receive a cycle reduction from 5 min to 60 sec? Or compression mold for parts tolerances of 0.05mm or less-which compression was incapable of due to bias problems? For free DFM analysis in 2-3 business days, Engelhardt includes the ideal material, taking into account your Shore A (5-80A for LSR), volume, tolerance class, and sterilization specification. Use the decision matrix detailed in Section 3 for a starting point.

03 Challenge 3: Quality Uncertainty with Overseas Silicone Rubber Suppliers

Chinese sourcing of silicone rubber parts-initial consistency concerns. This is a legitimate concern for manufacturers that do not incorporate process controls. Engelhardt carries both ISO 9001:2015 and IATF 16949-the automotive quality standard that mandates documented PPAP, SPC monitoring, and complete batch traceability. Every rubber incoming lot has a Mooney Viscometer and Moving Die Rheometer tested before it even arrives to the press. Kohler, American Standard, Amphenol-we have their brands and an annual audit on our presence.

04 Challenge 4: High Tooling Investment with No Volume Guarantee

The multi-cavity LSR mold—the $15,000-$80,000—is significant in that it makes a tool investment buyer confident that the investment is protected. With Engelhardt prototype runs from 100 pieces on single-cavity tools at the $8K-$15K range that fully transfer the investment of the mold to the customer, you get to retain ownership and we maintain it for free during the first year. As quantities increase, we build production molds with amortization schedules through to short breakeven within 12-18 months on typical production volumes.

Engelhardt LSR Injection Molding — Capabilities & Equipment

We have 53,000 sqm of Silcone rubber injection molding processing capacity over three manufacturing sites. Our LSR injection cell has a separate processing cell from our solid silicone & rubber compression lines (medical & food grade parts production in a clean environment for both). Here is the reality of the shop floor:

Ausrüstung	Specification	Anwendung
LSR Injection Machine	150T, precision metering system + static mixer	Complex LSR parts, multi-cavity molds up to 64 cavities
Vacuum Press (LSR)	250T, heated platen + vacuum chamber	Bubble-free LSR molding, optical-grade parts
Large Vacuum Press	1200T, oversized platen	Industrial gaskets, seals up to 2200×1200mm
Feststoff-Silikon-Injektion	300T	HCR parts, high-durometer (>80A) components
Vulkanisiermaschinen	40+ units, 50–400T range	High-volume production, multiple parallel runs
Formwerkstatt	3,600 sqm — German Rhodes CNC, EDM, wire-cut	In-house tooling, mold iteration in 3–5 days

The LSR Injection Molding Process at Engelhardt

In fact, our LSR molding is performed in a closed loop between the raw material and the finished part.

01 Two component metering

Part A (base polymer) and Part B (platinum catalyst) are pumped via a valve controlled dosing unit, to a stoichiometrically correct 1:1 ratio. The ratio accuracy is checked to 0.5% W/W.

02 Static mixing & injection

Components are pre-mixed in a static mixer and then injected via a cold runner system into the heated mould (150-200C). Cold runner technology results in zero material waste in the delivery system, each gram of LSR enters the cavity.

03 Platinum catalyzed cure

The addition cure reaction cross-links the silicone in between 30-90 seconds depending on wall thickness. No peroxide byproducts, no postcure for most grades.

04 Automated demolding

Robotic part removal provides repeatable cycle times and removes variance due to operator actions. Normal operation for these cells is 24 hours/day, 7 days/week, monitored by a single operator on 4 machines.

Engineering Note: Valve Gate vs. Open Nozzle

Valve gate cold runner systems specified on parts where zero vestige on the gate area is critical. Open nozzle systems are 20-30% less expensive in tooling but leave a small witness mark. Valve gate is necessary on medical seals and visually exposed consumer parts, while open nozzle saves tooling cost on industrial gasket without sacrifice of function.

Material Selection Decision Matrix

Faktor	LSR (Liquid)	HCR (Solid Silicone)	Compression Silicone
Shore Hardness Range	5 80A	20 –90A	30–80A
Achievable Tolerance	±0.025–0.05mm	±0.08–0.15mm	±0.1–0.2mm
Typische Zykluszeit	30 –90 Sek	120–300 sec	180–600 sec
Ideal Production Volume	10,000+ pcs/yr	1,000–50,000 pcs/yr	100–5,000 pcs/yr
Werkzeuginvestitionen	$15K–$80K	$8K–$30K	$3K–$15K
Flash Level	Flashless (cold runner)	Medium (trimming needed)	Significant deflashing
Automation Potential	Fully automated cells	Partial automation	Manual / Semi-auto
Material Waste	<1%	3–5%	5–15%
Part Complexity	High (thin walls 0.3mm+, undercuts)	Mittel	Simple geometries
Surface Finish	Ra 0.2–1.6μm	Ra 0.8–3.2μm	Ra 1.6–6.3μm

Maximum Capabilities

Max Mold Size

2200×1200mm (largest one of all the LSR capable molds in South China)

Max Part Weight

Up to 5kg per shot

Multi-cavity

Up to 64 cavities, small seals & O-rings

Color Matching

Pantone/RAL custom pigmentation with masterbatch blending

Überformen

LSR-to-metal and LSR-to-plastic, using primer or plasma treatment

LSR vs Compression Molding vs Transfer Molding — Performance Comparison

The process selected sets your per-part cost, achievable tolerance, and volume of production for the next five to ten years. This part provides the numbers to make the call without a sales pitch. Every number below is the state of production—not laboratory perfection.

Three-Process Head-to-Head

Parameter	LSR-Spritzguss	Kompressionsformen	Transferformen
Material Form	Liquid (self-leveling, pumped)	Solid preform (pre-weighed)	Solid preform (pot-loaded)
Cure Chemistry	Platinum-catalyzed addition cure	Peroxide or platinum	Peroxide or platinum
Mold Temperature	150 200°C	160–200°C	160–200°C
Zykluszeit	30 –90 Sekunden	3 15 Minuten	2 – 8 Minuten
Part Tolerance	±0.025–0.05mm	±0.1–0.2mm	±0.05–0.1mm
Flash Generation	Flashless (valve gate)	Significant (deflashing required)	Mäßig
Automation Level	Fully automated cells	Manual / Semi-automated	Semi-automated
Ideal Volume	10,000+ parts/year	100–5,000 parts/year	1,000–25,000 parts/year
Werkzeugkosten	$15K–$80K	$3K–$15K	$8K–$30K
Material Waste	<1% (cold runner)	5–15% (flash + overflow)	3–8% (sprue + flash)
Part Complexity	High (thin walls 0.3mm+, undercuts)	Simple to medium	Medium complexity
Surface Finish	Ra 0.2–1.6μm	Ra 1.6–6.3μm	Ra 0.8–3.2μm
Typische Anwendungen	Medical seals, auto connectors, precision gaskets	Large gaskets, pads, thick parts	Insulators, medium-complexity parts

When to Choose Each Process

Use LSR injection molding if:

Yearly volume is greater than 10,000 parts AND tighter tolerances than 0.05mm are required AND there are thin wall shapes, undercuts, or multi cavity efficiency aspirations.

Choose compression molding when:

Volume stays below 5,000 parts/year AND geometry is simple (flat gaskets, thick pads) AND tooling budget is constrained below $15K.

Choose transfer molding when:

Volume is 1,000–25,000 AND you need better flash control than compression but cannot justify full LSR injection tooling investment.

LSR (Thermoset) vs Thermoplastic Injection — Process Difference

Buyers sometimes compare LSR injection molding to standard plastic injection molding. The processes use opposite thermal logic:

Faktor	LSR (Thermoset)	Thermoplastic Injection
Temperature Direction	Cold material → heated mold (150–200°C)	Hot material (200–350°C) → cold mold
Cure Type	Irreversible crosslinking (permanent)	Reversible melting
Operating Range	-60°C to +200°C continuous	Limited by Tg / HDT
Flexibility Retention	Maintains elasticity across full temp range	Becomes brittle at low temps
Biokompatibilität	Inherent (platinum-cured, no leachables)	Requires additive qualification
Recyclability	Not recyclable (crosslinked)	Fully recyclable (regrind)

The irreversible curing process is why LSR silicone rubbers maintain their seal integrity, elongation (up to 950%), and chemical resistance across decades of service—properties that thermoplastics cannot match in demanding elastomer applications.

Have a part currently made by compression or transfer? We can assess whether LSR conversion makes economic sense.

Kostenlose DFM-Analyse anfordern

Client Results: 60% Faster Cycle Time with Engelhardt LSR

Results from active production programs. Metrics reflect sustained performance over 6+ month production periods, not single-run samples.

Sanitaryware Valve Seals — Compression to LSR Conversion

Client:

Fortune 500 sanitaryware brand (faucet valve seals)

Challenge:

Their existing compression-molded valve seals ran 8-minute cycles with a 12% scrap rate from flash and short-fill defects. Annual scrap cost exceeded $180,000 across 3 million parts/year.

Engelhardt Solution:

Designed a 16-cavity cold runner LSR mold with automated demolding. Converted the part from HCR compression to platinum-cured LSR injection without geometry changes.

Production Results

Zykluszeit: 8 minutes → 55 seconds (89% reduction)
Scrap rate: 12% → <1% (flash-free molding)
Tolerance improvement: ±0.15mm → ±0.03mm on critical sealing surfaces
Estimated annual savings: $200K+ (scrap + labor + cycle efficiency combined)

Automotive Connector Seals — Full IATF Traceability

Client:

Global electrical connector manufacturer (automotive tier)

Challenge:

Required IATF 16949-compliant traceability with CPK >1.67 on critical dimensions. Volume target: 100,000+ seals per year with zero field failures.

Engelhardt Solution:

Built a total automated LSR injection cell with robotic demolding, inline dimensional inspection, and complete batch to part traceability through our MES system.

Production Results

Full PPAP documentation package (Levels 1–5)
CPK >1.67 maintained on all critical dimensions for 18 months
0 PPM filed returns in first 12 months of production
Passed 3 consecutive customer audits without corrective actions

Industrial Large-Format Gaskets — Single-Piece Molding

Client:

Industrial equipment manufacturer (800×600mm gasket)

Challenge:

Gasket required a size beyond most suppliers mold size capability. Past solution: 4-section assembly. Chemical environment caused joint failures in 6 to 12 months.

Engelhardt Solution:

Specs required a 2200x1200mm mold. Capital equipment purchased (1200T press) to produce the gasket as a single moldin. No bonded joints.

Production Results

Single-piece construction: zero joint failures
Material/service life increased from 12 months to over 36 months in challenging chemical environments
5-year cumulative savings from reduced replacement frequency

60%+

Average cycle time reduction when converting from compression to LSR injection molding

Based on Engelhardt client production data, 2022–2025. ROI Card: Silver tier (industry-benchmarked TCO data).

Industry Application Matrix

Industrie	Typical Parts	Key Requirement	Engelhardt Advantage
Automobil	Seals, connectors, vibration dampeners	IATF 16949, -40°C to +200°C	Certified + 150T dedicated LSR cell
Sanitaryware	Ventildichtungen, O-Ringe, Duschkomponenten	NSF/FDA-grade, 10-year durability	Kohler / American Standard track record
Elektronik	Keypads, connector boots, EMI gaskets	Precision ±0.03mm, Shore 30–70A	CNC/EDM in-house tooling
Industriell	Large gaskets, bellows, diaphragms	Chemical resistance + oversized format	2200×1200mm mold + 1200T press
Consumer	Wearables, kitchen tools, baby products	Biocompatible, colorable, skin-safe	Pantone matching + USP Class VI materials

Working on a similar application? Let us show you what Engelhardt can do for your geometry and volume.

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Quality & Compliance — ISO 9001 · IATF 16949

Certificates document that a manufacturer passed an audit. Testing procedures/system documentation confirm that they maintain quality-system when out of sight. That is what Engelhardt runs on every production day.

ISO 9001:2015

Qualitätsmanagement

IATF 16949

Automotive Quality

13+ Years

Manufacturing Since 2011

53,000 sqm

Production Facility

500+ Staff

Including 80+ Engineers

Testing Equipment Inventory

Ausrüstung	Function	Stage
Mooney-viskosimeter	Raw material viscosity verification	IQC — incoming batch testing
Moving Die Rheometer (MDR)	Cure rate & crosslink density measurement	Material qualification + process setup
Carbon Black Analyzer	Filler content verification	Material composition audit
Universal Testing Machine	Tensile strength, elongation at break, tear resistance	Finished part mechanical properties
Shore A/D Durometer	Hardness measurement (±1 Shore point)	In-process + final QC
Compression Set Tester	Long-term deformation resistance under load	Seal and gasket qualification

Quality Process Flow: IQC → IPQC → FAI → OQC

IQC (Incoming Quality Control): Each rubber batch tested with Mooney Viscometer + MDR + Carbon Black analysis prior to release to production. Reject rate: 3% of all batches tested.

IPQC (In-Process Quality Control): SPC monitoring critical dimensions, cavity weight documentation, visual sampling per customer plan.

FAI (First Articles Inspection): Dimensional report (GD&T) + material certification + cure validation on first 5 pieces of every new mold and changeover.

OQC (Outgoing Quality Control): AQL sampling per Ikegaw Bammers-1. Customer specific sampling procedures available.

Traceability: Batch mold number operator timestamp. Complete chain trace back in 4 hours.

Our LSR development team has over 30 years experience designing original molds. Spend what you save on production to get the finest German tooling into production with our in-house specialists. Over 500 projects completed in automotive, sanitary and electronic markets. Every toolts goes through trial and inspection approval before customer demonstration.

— Engelhardt LSR Engineering Team

Pricing Framework

Cost of LSR injection molding depends on mold complexity, part volume, material grades, secondary operations.

Cost Component	Range (USD)	Key Factors
Mold Tooling	$8,000–$60,000	Cavity count, complexity, steel grade (P20/H13/S136), surface finish
Per-Part (1,000 qty)	$0,50 $5,00	Part size, material cost ($15–35/kg), cycle time, secondary ops
Per-Part (10,000 qty)	$0.20 $3.00	Volume discount, optimized multi-cavity cycle
Per-Part (50,000+ qty)	$0.10 $2.00	Maximum efficiency, 16–64 cavity molds
DFM Analysis	FREE	Included with every inquiry — no obligation
T1 Sample Run	Included in tooling	First 50–100 pieces for dimensional approval

Lead Time Breakdown

Phase	Timeline	Deliverable
DFM Review	2–3 business days	Design feedback + material recommendation report
Formdesign	5–10 days	2D/3D mold drawings for customer approval
Mold Fabrication	15–25 days	Steel mold + polishing + assembly + trial shot
T1 Samples	3–5 days	First articles + dimensional inspection report
Production (per batch)	7–15 days	Full QC inspection per batch + shipping prep
Total New Project	30–50 days	Inquiry to first shipment
Repeat Orders	7–15 days	Existing mold, standard scheduling

5-Step Engagement Process

Fordern Sie ein Angebot an

Upload 3D/2D files (STEP, IGES, PDF) + target volume + material preference. Response within one day.

Free DFM Analysis

use our engineers experienced with geometry, wall thicknesses, draft angles, gate location. Expect to receive your report in 2-3 days.

Estimate

Itemized list of costs Tooling/parts/ shipping. Valid for 30 days.

Approve new tool

T1 samples with dimenstional validation prior to production.

Mass Produce & delivery

Own shipment report. your project English speaking headquartered project manager.

After-Sales Support

Manage mold: In house is included in the tooling fee for 12 months. Mold maintenance post year 1 is commissioned on a piece by piece basis.
Mold ownership: Customer owns fully. Zegbrk_molds suppliedd ready to plug and play. molds may be transferred to customer for delft.
Engineering iterations: Significant geometry changes requote, minor gate/venting adjustments free.
Account manager: Dedicated English speaking GM assigned to each customer account. direct WeChat/WhatsApp/e-mail.
Reorder process: Simplified order process with 7-15 day cycle. organized scheduling of blanket purchase orders.

MOQ Policy

Prototype/sampling: 100 pieces minimum (single-cavity tool)
Production: 1,000 pieces recommended (cost-optimal point)
No maximum: Annual blanket orders with scheduled releases supported

LSR Engineering & Procurement Tools

Leverage our proprietary calculators to optimize your material selection and evaluate project economics instantly based on real-world production data.

LSR-Materialauswahlrechner

Input your Shore A hardness, temperature requirements, and application environment to receive instant, data-driven LSR grade recommendations and detailed process parameters.

Launch Calculator →

LSR vs Alternative Process Estimator

Compare the Total Cost of Ownership (TCO) between LSR injection, compression, and transfer molding based on your annual volume and specific part complexity.

Launch Estimator →

LSR Injection Molding FAQ

How much does an LSR injection mold cost?

LSR mold tools range from $8,000 to $60,000 depending on cavities, parts, steel quality and desired surface etc. simple single cavity prototyping tooling can cost from 8-15k$ to more complex cold runner multi cavity tooling 25-80k$. Engelhardt does itemized tooling quotation and quotes within 3 days of receipt of 3d file.

What is the difference between LSR and HCR (High Consistency Rubber)?

What is the difference between HCR and LSR? Liquid silicone rubber injection molding uses a cold, liquid, low viscosity two-part platinum catalyzed compound that is pumped and metered into heated molds (150200C). Takes 30-90seconds and can achieve 0.025mm tolerances. HCR is hot solid material, preformed, and loaded manually. Uses a peroxide or platinum cure, cycle time of 2-5 minutes and 0.08mm tolerances possible. Use LSR for high volume precision parts (>10K per year). Use HCR for lower volume, extremely hard parts (>80Shore A), or when tooling costs need reduced.

Can silicone rubber be injection molded?

Whether you can do this with silicone? Yes – Liquid silicone rubber (LSR) injection molding. A two part platinum catalyzed system is injected into heated moulds of 150-200 degrees celsius. A flashless, high precision process with fully automated potential. Unlike the regular thermoplastic injection process (hot material in a cold mould), the injecting of cold material into a heated one results in essential crosslinking, permanent elasticity which is stable from -60 to +200 °Celsius. Performing this in the new WAY.

What tolerances can LSR injection molding achieve?

What is the tolerance I should expect? Typical critical dimension tolerance on LSR injection molding will be approximately 0.0250.05mm, if the optimum mold design is used a balanced cold runner, stable 1 degree Celsius (1C) temperature, installation of SPC process controls and the application of a quality valve gate, under these conditions 0.02mm can be achieved. Degree of tolerance is affected by wall thickness distribution, gate position, gate type, mold thermal stability, part design. Engelhardt will provide you with CPK data on your critical dimension.

What is the minimum order quantity for LSR molded parts?

Max order quantity? Does not matter. Orders can be taken of prototype quantities from 100 units using single cavity tooling for direct insertion. Produces minimum efficient order volume of 1, 000 units (before per-unit-cost get smaller because of set-up load sharing). Blanket orders out 12 months available with regularly scheduled monthly and quarterly discharges. high-volume accounts production models are supported 40+ vulcanizers and 150T LSR cell.

How long does LSR mold fabrication take?

Time frame? 15-25 days until T1 sample ready after design approval. total cycle new mold production takes 30-50 days from first inquiry to first shipment. repeat runs on existing models 7-15 days depending on batch size. 3600sqm, 50+ staff, 16 presses are German Rhodes machining robots, in-house.

What is the difference between silicone and plastic injection molding?

Silicone (thermoset) injection molds—cold liquid injected into a heated (150200C) mold, where irreversible chemical crosslinking takes place. The rate of crosslinking crosslinks sets the final elastomer in a flexible state from -60C to +200C. Plastic (thermoplastic) injection molds—hot melted resin (200350C) injected into a cold mold, where it cools and solidifies. Unlike silicone, thermoplastics can be remelted and recycled. LSR uses different injection mold equipment: metering pumps, cold runner delivery, different (heated) platens in a mold press.

What industries use LSR injection molded parts?

Major end markets include: automotive (performance seals, connector boots, vibration dampeners), sanitaryware (valve seals, O-rings, shower parts), electronics (gasketing for keypads, EMI gaskets, connector boots), medical (implant parts, drug-delivery seals, surgical instrument grips), consumer (wearables, baby products, & kitchen utensils), industrial (large gasketing, diaphragms, bellows, etc). LSR parts are used anywhere biocompatibility is needed, where temperature extremes or prolonged compression are needed.