Shenzhen Alu Rapid Prototype Precision Co., Ltd.
Industry News
Short answer: For 1 to 50 parts that must look and behave like injection-molded production, choose vacuum casting (urethane casting) — silicone tooling costs a few hundred dollars instead of thousands. Once you need 1,000+ parts, or the material must be a true production thermoplastic, move to injection molding.
Both processes fill a mold with liquid material. The difference is the tool: soft silicone versus hardened steel.
At a Glance
| Factor | Vacuum Casting | Injection Molding |
|---|---|---|
| Mold material | Silicone (soft) | Steel / aluminum (hard) |
| Tooling cost | $100–$1,000 per mold | $3,000–$80,000+ |
| Mold life | ~15–25 parts | 100,000+ parts |
| Economical quantity | 1–50 parts | 1,000+ parts |
| Tooling lead time | 2–5 days | 4–8 weeks |
| Material | Polyurethane resins (near-ABS/PP/PC) | True thermoplastics |
| Best for | Design validation, pre-production, pilot builds | Mass production |
How Vacuum Casting Works
A master pattern (usually 3D printed or CNC machined) is suspended in a box, and liquid silicone is poured around it. Once cured, the silicone is cut open, the master removed, and the cavity becomes the mold. Polyurethane resin is then mixed, degassed, and poured into the mold under vacuum — which removes bubbles and produces parts that look injection molded.
The same mold can produce 15–25 parts before the silicone degrades. A single master yields multiple molds, so a run of 100 parts is typically made from 5–8 molds.
Cost Comparison
| Quantity | Vacuum Casting (approx.) | Injection Molding (approx.) |
|---|---|---|
| 1 part | $100–$400 total | Tooling + first part — not economical |
| 10 parts | $30–$120 per part | Tooling dominates |
| 50 parts | $25–$80 per part | Rarely economical yet |
| 1,000 parts | Not practical (tool life) | $3–$15 per part |
Vacuum casting wins whenever the tooling cost of molding cannot be amortized — which is most projects before design freeze.
Where Vacuum Casting Wins
Design and market validation before committing to steel
Pilot builds, trade-show units, and sales samples
Overmolding and multi-part assemblies in matching color and texture
Parts with fine texture, paint, or color requirements
Small runs where per-part cost matters less than total cost
Where Injection Molding Wins
Production volumes above roughly 1,000 units
Parts that must use a specific production-grade thermoplastic
Long-term consistency, certification, and repeat orders
High-strength or chemically resistant applications
Material and Performance Differences
This is the most common misunderstanding. Vacuum casting uses polyurethane resins formulated to mimic ABS, PP, PC, and rubber — they look and feel like production plastic, and are excellent for fit, form, and appearance. But they are not identical to the production thermoplastic. Mechanical properties, UV stability, and long-term aging can differ.
If your validation depends on precise impact strength, chemical resistance, or regulatory compliance, the final material must be verified in the real production process.
The Standard Development Path
CNC or 3D-printed prototype — check form and fit in a real material
Vacuum casting, 10–50 parts — validate appearance and function for users, beta sites, or investors
Injection molding — once volume and design justify the tool
See our vacuum casting capabilities and rapid prototyping services to plan the first two stages.
FAQ
How many parts can one silicone mold produce?
Typically 15–25 parts before surface detail and dimensional accuracy begin to degrade.
Are vacuum-cast parts as strong as injection-molded parts?
They are strong enough for fit and function testing, but polyurethane properties are not identical to production thermoplastics. Verify critical performance in the final process.
How fast can I get vacuum-cast parts?
Often 3–7 days after the master pattern is approved, versus 4–8 weeks for a production mold.
Can vacuum-cast parts be painted or textured?
Yes. Textures are transferred from the master pattern, and parts can be painted, dyed, or finished to match a target appearance.
When should I stop using vacuum casting?
When you need more than a few hundred parts, a production certification, or a specific engineering thermoplastic.
Get a Quote
Send your CAD file and target quantity — we will tell you whether vacuum casting or injection molding gives the better total cost, and quote both if useful.