Vacuum Casting in China — Complete Guide for Prototypes and Small Series
Vacuum casting (silicone molding or urethane casting) is one of the fastest ways to produce 10-100 functional prototypes without the cost and lead time of production tooling.
Key Metric: A typical vacuum casting project: 10-15 working days from master pattern to 50 finished parts, at 5-15% of the cost of a steel injection mold.
The Process (6 Steps)
- Master pattern: SLA/SLS 3D print, sanded and finished
- Silicone mold poured under vacuum, cured 4-12 hours at 40-70 C
- Mold cut along parting line; master removed
- Polyurethane resin degassed and poured under vacuum
- Oven cure at 50-80 C for 30-60 minutes
- Demold, trim gates, surface finish
Polyurethane Resin Types
| Type | Properties | Simulates |
|---|
| Rigid PU | High stiffness, paintable | ABS, PC, PP, PA |
| Flexible PU | Rubber-like, Shore A 30-90 | TPU, TPE |
| Transparent PU | Optically clear | PMMA, PC |
| High-temp PU | Heat deflection to 120 C | PBT, PPS |
| Flame-retardant PU | UL 94 V-0 rated | Flame-resistant plastics |
Surface Finishing
- Painting: RAL/Pantone matching, matte/gloss/textured
- Rubber painting: Soft-touch coating
- Screen printing: Logos, labels
- EMI shielding: Conductive paint on internal surfaces
- Texture: Leather, woodgrain, fine matte from textured masters
Typical Pricing (China)
| Part Size | Silicone Mold | Per Part (50 pcs) | Total (50 pcs) |
|---|
| Small (matchbox) | $80-150 | $5-10 | $330-650 |
| Medium (hand size) | $150-350 | $10-25 | $650-1,600 |
| Large (helmet size) | $350-800 | $25-60 | $1,600-3,800 |
Clusters
- Shenzhen: Fastest turnaround, strong supporting services for assembly
- Kunshan: Higher quality focus, automotive/aerospace prototype work
- Shanghai area: Premium pricing but strong English communication
Advantages vs. Injection Molding
| Factor | Vacuum Casting | Injection Molding |
|---|
| Tooling cost | $100-800 | $2,000-50,000 |
| Tooling time | 3-7 days | 3-12 weeks |
| Quantity optimum | 5-100 parts | 500+ parts |
| Materials | PU resins (ABS/PC-like) | All thermoplastics |
Sourcing Tips
- 3D print the master locally and ship to China, or let the casting shop print it
- Ask for vacuum casting in the quote not prototype injection molding for small quantities
- Silicone mold typically lasts 20-40 casts before degrading
- Specify finish requirements: painted, textured, or as-cast
- Request UV-resistant resin for outdoor-use prototypes