Vacuum Casting Services
Professional online urethane casting services for prototypes and end-use production parts. Deliver precision-engineered components with intricate geometries, tight tolerances, and exceptional surface finishes. Ideal for short-run manufacturing, our process ensures production-level quality at competitive lead times, bridging the gap between prototyping and full-scale production.
What is Vacuum Casting？
Vacuum casting (also called urethane casting or polyurethane casting) is a process that uses a flexible silicone mold to produce small batches of parts with material properties and surface quality equivalent to injection-molded plastic.
The process begins with a high-quality master pattern (typically CNC machined or SLA printed). Liquid silicone is poured around the master in vacuum to create a mold. Two-component polyurethane resin is then cast into the silicone mold under vacuum — the vacuum prevents air inclusion, giving bubble-free, high-integrity castings.
How is vacuum casting different from injection molding?
Vacuum casting uses silicone molds (flexible, low cost, 15–20 shot life) vs. injection molding’s steel molds (rigid, expensive, millions of shots). Vacuum casting is ideal for 5–100 parts; injection molding for 1,000+ parts.
What's the dimensional accuracy of vacuum casting?
Typically ±0.1% of part dimension (minimum ±0.2mm). This is inherently less precise than CNC (±0.01mm) due to silicone elasticity and thermal shrinkage, but acceptable for most product validation purposes.
How many parts can I get from one silicone mold?
Typically 15–20 parts for standard geometries and opaque colors. Complex undercuts or clear/transparent parts typically yield 10–12 parts before the mold degrades.
Why Choose Samshion Vacuum Casting?
Full In-House Process
Master pattern fabrication → silicone mold making → vacuum casting → post-processing — all at our facility. No outsourcing means faster turnaround and consistent quality.
30+ Urethane Materials
From rigid ABS-like to soft rubber-like (Shore A 30–90), transparent optical quality, flame-retardant, glass-filled — we stock 30+ two-part PU materials to match your requirements.
50% Below US/EU Cost
Same quality vacuum cast parts at 40–60% less than Western service bureaus. China manufacturing advantage with fast DHL courier to your door.
Production-Quality Finish
Silicone molds faithfully replicate the master pattern surface — SPI A1/A2 gloss, matte, textured, and overmolded surface finishes all achievable.
Multiple Color Variants
One silicone mold can produce parts in multiple colors by adding different pigments to the casting resin — ideal for color family validation without additional tooling.
5–15 Day Delivery
Standard lead time from approved STEP file to delivered parts: 5–15 business days including master fabrication, mold making, casting, and post-processing.
How Vacuum Casting Works — Step by Step
A 4-stage process from master pattern to delivered parts
Master Pattern Creation
We fabricate a high-precision master pattern — typically SLA 3D printing (±0.1mm accuracy) or CNC machining for critical-dimension parts. The master is hand-finished and polished to the exact surface quality required on the final cast parts.
- SLA for complex organic shapes, CNC for tight-tolerance masters
- Hand-finishing and polishing to final surface specification
- Quality check against your 3D model before mold pour
- Texture application if required (EDM-spark, grain, matte)
Silicone Mold Fabrication
The master is suspended in a casting frame and liquid silicone (Shore A 20–30 hardness) is poured around it under vacuum to eliminate air bubbles. After 8–16 hours of room-temperature curing, the silicone block is cut along a predetermined parting line.
- Vacuum de-gassing eliminates air voids in mold
- Parting line designed to minimize witness marks
- Vent and pour gate locations optimized for part geometry
- Mold life: 15–20 casts (standard), 10–12 (complex/clear)
Urethane Resin Casting
Two-component polyurethane resin is precisely weighed, pigmented, and poured into the mold in a vacuum casting chamber (<50 mbar). The vacuum eliminates air entrapment. Parts cure at 60–70°C for 20–45 minutes.
- Full vacuum (<50 mbar) eliminates porosity and air bubbles
- Precise resin mixing (±1g) ensures consistent properties
- Oven cure at 60–70°C for full mechanical properties
- ~45 min cycle time per cast including de-mold
Post-Processing & QC
De-molded parts are inspected, cleaned, and post-processed per specification. Gate marks are removed. Painting, texturing, heat-set inserts, and assembly operations completed in-house.
- 100% visual inspection of every cast part
- Dimensional check on first article and random samples
- Painting (primer + topcoat) with color matching service
- Heat-set threaded inserts, overmolded grips, assembly available
Vacuum Casting Urethane Materials
Rigid Materials (ABS / Nylon-like)
Standard Rigid PU (ABS-like)
Shore D 75–85, tensile 40–55 MPa, most common choice
Glass-Filled Rigid PU
Shore D 80–90, higher stiffness, simulates PA+GF
High-Impact Rigid PU
Shore D 70–80, improved impact resistance vs standard
Flame-Retardant PU (UL94-V0)
Shore D 75, self-extinguishing, electronics enclosures
High-Temperature PU (HDT >90°C)
Shore D 80, heat-deflection for under-hood testing
Flexible & Transparent
Soft Rubber PU (Shore A 30–60)
Very flexible, tactile grip, simulates TPE/silicone
Semi-Rigid PU (Shore A 70–90)
Soft-touch feel, living hinges, flexible housings
High-Clarity Transparent PU
≥85% optical clarity, lens covers, fluid windows
Colored Transparent PU
Tinted transparent in any hue, signal light covers
Two-Shot Overmold Combinations
Rigid substrate + soft overmold in one casting cycle
Vacuum Cast Part Surface Finishes
As-Cast (from mold)
Replicates master
Surface quality directly from silicone mold — as good as master pattern surface
Primed + Painted
Any RAL/Pantone
2K urethane primer + color + clear coat. Professional color-matched appearance
Texture / Grain
From master
Mold replicates any texture applied to master: leather grain, orange-peel, matte
Transparent / Polished
≥85% clarity
Clear PU resin parts polished to remove minor surface marks, improve clarity
Metallic Finish
Vacuum metallize
Decorative chrome-look using vacuum metallization over base paint
Pad Printing / Silk Screen
Logo & text
Add product logos, compliance marks, and surface graphics to cast parts
Insert Installation
Brass heat-set
Brass threaded inserts (M2–M10) heat-pressed into cast parts for thread fastening
Assembly & Packaging
Full service
Multi-part assemblies completed and retail-packaged ready for trade show or review
Vacuum Casting Design Guidelines
Design Tips for Best Results
Minimum Wall Thickness ≥ 2mm
Walls thinner than 2mm may not fill completely or may warp during demolding. For very thin features, increase to 3mm where possible.
Draft Angles 1–3°
Add 1–3° draft to vertical walls to aid demolding from silicone mold. Without draft, thin ribs and deep walls may tear the mold during extraction.
Parting Line Placement
Work with our engineer to position the parting line (where the mold is cut open) on a non-cosmetic edge to minimize witness lines on visible surfaces.
Avoid Large Flat Surfaces
Large flat surfaces tend to show any minor surface irregularities. Add slight curvature (R5–R10mm) to help mask variation and improve aesthetics.
Design Considerations
Severe Undercuts Increase Mold Cost
Deep undercuts require complex mold parting or internal cores — discuss with engineer at enquiry stage to avoid late-stage design changes.
Tight Tolerances Not Achievable
Vacuum casting achieves ±0.1–0.3% (minimum ±0.2mm). If you need ±0.05mm, CNC machining is the right choice.
Very Long Thin Parts May Warp
Parts with extreme aspect ratios (L/W >10:1) can bow or warp during resin cure. Add stiffening ribs or cast in sections.
Overly Complex Internal Channels
Internal channels are very difficult — silicone can't be easily removed from complex internal passages. Consider split-and-bond approach.
Quality Control — Every Cast Part Inspected
Master Pattern Approval
Master measured against 3D CAD before mold pour. Customer can request first-article CMM report of the master pattern.
First Cast Inspection
First cast part from each mold fully inspected dimensionally and visually. Customer sign-off can be requested before batch production.
Visual QC Every Part
100% visual inspection — every part checked for voids, sink marks, short shots, and color accuracy before packing.
Dimensional Sampling
Random dimensional sampling on key features using calipers and CMM. Results logged per ISO 9001 traceability requirements.
Why Vacuum Casting Is the Smart Choice for 5–100 Parts
Cost-Effective Silicone Molds
Urethane casting utilizes affordable silicone molds, eliminating the need for costly metal tooling. This makes it ideal for producing high-quality prototypes and low-volume parts at a fraction of traditional manufacturing expenses.
Rapid Turnaround Times
Deliver up to 50 functional urethane parts within 10–15 days, accelerating product development cycles and meeting tight deadlines for prototyping or small-batch production.
Diverse Material Options
Choose from a wide range of polyurethane resins, including flexible, rigid, impact-resistant, or transparent formulations, tailored to mimic end-use material properties.
High Precision and Detail Replication
Achieve tight tolerances and intricate geometries with production-grade accuracy, ensuring cast parts match design specifications for functional testing or final use.
Superior Surface Finishes
Urethane casting delivers smoother textures and finer aesthetic details compared to CNC machining or 3D printing, reducing post-processing efforts for market-ready models.
Technical Guide for Urethane Casting
Standard Accuracy
Standard tolerance of ±0.15mm/100mm, with precision up to ±0.05mm for critical applications.
Silicone Mold Lifespan
Each mold produces 15–20 high-quality parts. Complex or clear parts may reduce output to 10–12 casts per mold.
Standard Lead Time
Deliver 50 units within 7–10 days, depending on part complexity and batch size.
Surface Finishes & Features
Options include color matching, textures, gloss/matte coatings, inserts, overmolding, and polished transparent finishes.
Maximum Part Dimensions
Accommodates molds up to 1.8m x 1.0m x 0.8m, suitable for large-scale prototypes and functional components.
Minimum Wall Thickness
Optimal wall thickness: 1.5mm–2.5mm. Minimum feasible thickness: 0.6mm for delicate geometries.
Applications of Vacuum Casting
Low-Volume Production / Short-Run Manufacturing
Vacuum casting is ideal for producing high-quality plastic prototypes and end-use parts in small batches (10–500 units). When injection molding is cost-prohibitive for limited quantities, this method delivers production-grade components weeks faster than traditional tooling. Advanced materials like polyurethane resins replicate the properties of ABS, PP, or rubber, enabling functional testing and market validation without upfront mold investments.
Aesthetic Models / Color & Texture Prototyping
Create visually precise models with customizable colors, textures, and finishes using silicone molds. Test multiple design iterations—such as matte, glossy, or metallic surfaces—by casting 10–15 units for internal reviews or client presentations. This process eliminates guesswork in final product aesthetics, ensuring alignment with brand guidelines before mass production.
Engineering Verification / Functional Testing
Vacuum casting supports cost-effective design validation and iterative modifications. Prototypes withstand mechanical stress, thermal exposure, and environmental simulations, providing reliable data for certifications or regulatory approvals. Low-cost tooling allows rapid adjustments, reducing risks before committing to high-volume manufacturing.
Marketing & Display Models
Produce photorealistic, functional models for trade shows, user testing, or digital campaigns. Urethane-cast parts mimic end-product quality, enabling client engagement and pre-launch feedback. Display units can be quickly updated for evolving designs, ensuring marketing materials stay current across brochures, websites, or exhibitions.
Vacuum Casting FAQ
How many parts can I get from one silicone mold?
Typically 15–20 parts for standard geometries and opaque colors. Clear/transparent parts or complex undercut geometries typically yield 10–12 parts before the mold needs replacement.
What is the minimum order quantity?
Minimum 5 pieces per order — the mold cost is spread across the batch, so fewer than 5 pieces makes the per-part cost very high. Sweet spot is 10–50 pieces per material/color.
Can I get different colors from one mold?
Yes — this is one of vacuum casting’s key advantages. You can cast parts in different colors by changing the pigment added to each resin batch. No additional tooling cost for color variants.
How accurate are vacuum cast parts compared to injection molded?
Vacuum casting achieves ±0.1–0.3% (minimum ±0.2mm), compared to injection molding’s ±0.05mm. For most product validation purposes — assembly, ergonomics, appearance — vacuum casting accuracy is sufficient.
Can you match our exact Pantone / RAL color?
Yes. We use spectrophotometer color matching to mix pigments to your specified Pantone or RAL code. We also provide color confirmation chips before casting to ensure color approval.
What's the largest part you can vacuum cast?
Up to approximately 650mm (longest dimension). Very large parts may require split-and-bond construction. Please share STEP files and we’ll assess feasibility at no charge.