What is Vacuum Casting?

Vacuum casting — also known as silicone mold replication or polyurethane casting — is the fastest way to turn one good prototype into twenty production-grade plastic parts, without cutting a single piece of tool steel. This guide explains what vacuum casting is, how the process works step by step, which casting materials are available (with the honest pros and cons of each), where the process is used, and when it beats 3D printing and injection molding.

Vacuum casting is a replication process that produces high-quality plastic and rubber-like parts in small batches, using a flexible silicone mold instead of a hard metal tool. A master pattern — usually 3D printed (SLA) or CNC machined — is embedded in liquid silicone rubber. Once the silicone cures, the mold is cut open, the master removed, and the cavity is filled with two-component polyurethane (PU) resin inside a vacuum chamber. The vacuum pulls the resin into every detail of the cavity and eliminates air bubbles, producing parts that closely mimic injection-molded quality.

The process goes by several names — vacuum casting, urethane casting, polyurethane casting, silicone mold replication — all describing the same technology. It occupies the sweet spot between 3D printing (best for one-offs) and injection molding (best for thousands), delivering typical batches of 5–50 parts per mold with production-like appearance and mechanical properties.

How the Process Works — Step by Step

Step 1 — Master pattern. A master model is produced by SLA 3D printing or CNC machining, then hand-finished to the exact surface quality the final parts should show. Whatever the master looks like — gloss, texture, engraving — every copy will inherit it.
Step 2 — Silicone mold making. The master is suspended in a mold box, and liquid silicone is poured around it and cured (typically 18–24 hours). The cured block is then cut along a planned parting line, and the master is removed, leaving a perfect negative cavity. Flexible silicone handles undercuts and complex geometry that would trap a rigid mold.
Step 3 — Vacuum casting. The two mold halves are reassembled and placed in the vacuum chamber. Degassed polyurethane resin — rigid, flexible, transparent, or colored — is poured into the cavity under vacuum, ensuring bubble-free, fully dense parts.
Step 4 — Curing and demolding. The filled mold cures in an oven, the part is demolded, and gates and flash are trimmed. One silicone mold typically yields 20–30 parts before detail degradation.
Step 5 — Finishing (optional). Parts can be painted, polished, chrome-plated, silk-screen printed, or laser engraved to production appearance.

Vacuum Casting Capabilities

Servicios	Detalles
Plazos de entrega	7–12 days (master + mold + first parts)
Typical Batch Size	5–50 parts per mold (20–30 typical mold life)
Accuracy	±0.1 mm for dimensions under 100 mm (±0.2% above)
Minimum Wall Thickness	0.5–1.5 mm depending on geometry
Hardness Range	35–100 Shore A (elastomers) to 45–85 Shore D (rigid)
Maximum Part Size	Up to ~850 × 550 × 600 mm; castings up to ~5 kg

Vacuum Casting Materials

The real power of the process is its material menu. Two-component polyurethane casting resins are engineered to imitate specific production plastics:

ABS-like resins (general purpose)

The workhorse: rigid, impact-resistant, easy to finish and paint. Pros: balanced strength and stiffness, excellent cosmetics, low cost. Cons: moderate heat resistance (~70–80 °C), limited UV stability without additives.

PC-like resins (polycarbonate simulation)

Rigid with higher impact strength and better temperature resistance (~100–120 °C). Pros: tough, dimensionally stable, good for functional housings and automotive parts. Cons: more brittle than real PC at thin sections, higher resin cost.

PMMA-like / transparent resins (clear casting)

Optically clear or translucent parts — lenses, light pipes, display windows, demonstrator housings. Pros: glass-like clarity after polishing, can be tinted. Cons: scratches more easily than glass, bubbles demand careful vacuum control, sensitive to UV yellowing without stabilizers.

TPE / rubber-like elastomers (35–100 Shore A)

Soft-touch grips, seals, gaskets, buttons, bumpers. Pros: wide hardness range, true elastomer feel, good for ergonomic testing. Cons: lower tear strength than production TPE, surface can be tacky without coating, limited temperature range.

Heat-resistant resins (up to ~140 °C)

For under-hood automotive, lighting, and industrial parts near heat sources. Pros: survives environments standard resins cannot. Cons: more brittle, darker natural color limits cosmetics, premium pricing.

PP-like / PA-like / POM-like resins

Simulate living hinges (PP), wear resistance (PA), or low-friction sliding parts (POM). Pros: let you validate snap-fits, gears, and clips realistically. Cons: each approximates rather than equals the real polymer; chemical resistance is lower than the genuine material.

Specialty grades

Flame-retardant (UL94 V-0 class) resins for electronics, food-contact grades, glass-filled resins for extra stiffness, and conductive grades. Pros: unlock certification-adjacent testing early. Cons: narrower processing windows, higher cost, sometimes reduced surface quality.

The material variety of vacuum casting: optically clear, rigid black, soft-touch, heat-resistant and colored cast parts.

Where Vacuum Cast Parts Go to Work

Automotive: dashboard and trim prototypes, lighting housings, air-vent and interior components for fit checks and show cars.

Medical devices: equipment enclosures, handles, and trial units for ergonomic evaluation and pre-clinical validation.

Consumer electronics: phone and remote-control shells, wearable housings, audio equipment — for market tests, crowdfunding campaigns, and trade shows.

Industrial equipment: covers, brackets, control panels, and low-volume end-use parts for machinery built in dozens, not thousands.

Aerospace & defense: cabin interior samples, non-structural fittings, and demonstration models.

Appliances & robotics: cosmetic prototypes and functional pilot-run components.

Vacuum Casting vs. 3D Printing vs. Injection Molding

Rule of thumb: one part to check the design — 3D print it. Twenty parts that must look and behave like the final product — vacuum cast them. Ten thousand parts — injection mold them.

Factor	Colada al vacío	Impresión 3D	Moldeo por inyección
Best quantity	5–50 (up to ~200)	1–10	1,000+
Herramientas	Silicone mold, days, low cost	None	Steel/aluminum mold, weeks, high cost
Per-part cost	Medio	High (flat)	Lowest at volume
Surface quality	Excellent (inherits master)	Layer lines visible	Excelente
Material fidelity	Simulates production plastics	Limited by print process	True production resin
Consistency across batch	Alta	Medio	Highest
Typical lead time	7–12 days	1–3 days	4–8+ weeks

Why Choose Vacuum Casting?

Low tooling cost. A silicone mold costs a fraction of an aluminum or steel injection mold — no five-figure commitment before the design is proven.
Fast turnaround. From master pattern to finished batch in about one to two weeks, versus 4–8 weeks for conventional tooling.
Production-grade appearance. Cast parts replicate the master’s surface exactly — gloss, texture, fine detail — making them ideal for market testing, exhibitions, and investor demos.
Wide material simulation. PU resins convincingly mimic ABS, PC, PMMA, PP, PA, POM, and soft TPE/rubber, so functional and ergonomic testing is meaningful.
Complex geometry friendly. Undercuts, thin ribs, snap-fits, and overmolded or insert-molded features (metal inserts, shafts, threaded bushings) are all feasible.
Color flexibility. Resins can be pigmented to RAL colors, made translucent, or optically clear.

Honest Limitations

Limited mold life. Soft silicone wears; expect 20–30 good shots per mold (fewer for large or heavily textured parts), so total volume is capped.
Higher per-part labor. Casting, curing, and demolding are manual operations — the per-part price cannot compete with injection molding at scale.
Shrinkage and tolerance drift. PU cure shrinkage (and silicone’s thermal expansion) means tolerances are good (±0.1 mm class) but not metal-mold tight.
Not true production material. PU simulates production plastics convincingly, but it is not chemically identical — final certification testing still requires molded production resin.
Edge definition limits. Very sharp corners and fine lettering can soften slightly; precise color matching across batches takes care.

Vacuum Casting Molding Surface Termina

Acabado estándar
- Opciones de tratamiento superficial para fabricantes de moldes.
Tal como fue moldeado
- Sin pulido secundario ni esmerilado. La pieza mostrará marcas de mecanizado.
Grabado láser
- Grabe números de pieza, logotipos y más en sus piezas.

Vacuum Casting Molding FAQs

El moldeado por inyección se realiza mediante la creación de piezas de plástico o metal dentro de un molde. Luego se retiran del molde como piezas completamente formadas.
Colada al vacío, on the other hand, is used for low-volume production, which means that parts are built layer by layer using processes such as deposition or sintering.

Not only plastics can be used for Colada al vacío molding, but rubber, TPU and TPE.

How to Get An Online Colada al vacío Quote?

When you request an Colada al vacío molding quote, you not only receive accurate pricing in a short period of time. and receive our manufacturing analysis. Our online quotation platform also provides you with gate and ejector pin layouts and a price curve tool to help you choose the best tool option for your project.