Vacuum Casting Services for Low-Volume Plastic Parts
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What is Vacuum Casting?
Vacuum casting is a production process in which a silicone mold is created from a master pattern — typically a CNC machined or 3D printed part — and liquid two-component polyurethane resin is poured into the mold under vacuum to produce cast parts with the geometry of the master. The vacuum environment removes air bubbles from the resin before and during casting, allowing the material to fill fine surface detail, thin sections, and complex internal geometries without voids or surface defects.
At Top Proto, master patterns are produced by CNC machining or SLA/SLS 3D printing to the geometry defined in your CAD file, with surface finishing applied to achieve the specified surface texture before the silicone mold is poured. The silicone mold captures the master pattern geometry and surface condition, reproducing both faithfully in every cast part. Each silicone mold produces approximately 20 to 25 cast parts before the dimensional accuracy of the cavity degrades below acceptable limits, at which point a new mold is poured from the original master.
Our Services
Top Proto is your go-to provider for advanced CNC machining, delivering high-precision parts across industries.
What's Vacuum Casting Process
01. Master Patterns
Top Proto develops a high precision master parts normally through 3D printing or CNC machining to establish the form and finish of the part.
02. Solicone Mold Casting
The master pattern is put into a liquid silicone mold in order to create a flexible instance of the pattern. This enables high detail and accuracy of replication.
03. Urethane Pouring and Finishing
Urethane resin is cast under vacuum in order to remove air bubbles. The part is completed after drying and checked to produce constant production parts.
Why Choose Top Proto for Vacuum Casting Services?
Vacuum casting at Top Proto bridges the gap between 3D printed prototype parts and injection molded production parts. The cast polyurethane resins we use closely simulate the mechanical properties of standard injection molding resins, allowing teams to conduct functional testing, regulatory submissions, and pre-production sales samples from cast parts rather than waiting for injection mold tooling.
We produce master patterns in-house on our CNC machining and 3D printing systems, which means master surface quality and dimensional accuracy are controlled directly by our engineering team before the silicone mold is poured. Our casting team applies pigmentation to match your specified color, inserts metal components and threads during casting, and applies post-cast surface finishing to achieve the specified appearance. Every batch of cast parts is inspected dimensionally before delivery, with inspection reports confirming that critical dimensions meet your drawing requirements.
Vacuum Casting Capabilities
Feature | Specification |
Maximum Cast Part Size | Up to 600 x 500 x 400mm per cast cycle |
Dimensional Accuracy | +/-0.3% of nominal dimension; minimum +/-0.2mm on small features |
Parts Per Mold | Approximately 20 to 25 cast parts per silicone mold before mold replacement |
Batch Size | Minimum 5 parts per resin type; standard batch 20 to 50 parts; up to 100 parts from a single mold |
Cast Wall Thickness | Minimum 1.0mm for rigid resins; minimum 0.8mm for flexible resins in simple geometries |
Master Pattern Sources | CNC machined master (highest surface quality); SLA 3D printed master; SLS 3D printed master for functional geometry |
Color Options | Standard colors available; custom pigmentation to RAL or Pantone specification available at additional lead time |
Insert Casting | Metal inserts, threaded studs, and overmolded components can be placed in the mold before casting |
Industry Expertise at Top Proto
Rapid Tooling
Production Tooling
Materials for Vacuum Casting Services
Vacuume Casting Surface Finishes
Achieve the exact functional and aesthetic requirements for your machined components with our industry-leading finish gallery.
Our Vacuum Casting Gallery Parts
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Engineering Materials Available
Pros of Vacuum casting
- High Accuracy & Detail:Our milling process ensures that every component is cut to exact specifications, delivering a smooth, high-quality surface finish.
- Isotropic Mechanical Strength: Milled components are robust in every direction, making them ideal for high-volume production runs that require consistent structural integrity.
- Material Efficiency:Precision cutting paths minimize waste, and any unused material can often be repurposed or recycled efficiently.
- Complex Geometries:Advanced 3-axis and 5-axis milling eliminate the need for complex support structures, allowing for intricate designs to be manufactured directly.
What Makes Top Proto Different from Others
Choose Us for Flexible Pricing and Quick Delivery
At TOP PROTO, we know price and timeline go hand in hand. Our CNC machining services can work around your budget and deliver on your deadline. Get a quote instantly and select the service to meet your requirements.
- Competitive pricing with quality always remains.
- Fast lead time to complete the project quickly.
How We Works – 3-Stages Workflow
We guarantee that CNC parts are delivered on time and that the process is completely transparent in the following 3 simple steps:
Upload Your Files
Instant prices with DFM feedback for many file types.
We Manufacture Your Parts
You can select from many materials and methods.
Tracking and Receiving Your Parts
View the QC documentation and inspection photographs.
Frequently asked questions
How many parts can be produced from a single silicone mold?
A standard silicone mold produces approximately 20 to 25 cast parts before the cavity geometry degrades below acceptable dimensional limits. For programs requiring more parts, additional molds are poured from the original master pattern. The master pattern is retained in our facility for the duration of your program.
How accurate are vacuum cast parts compared to injection molded parts?
Vacuum cast parts achieve dimensional accuracy of +/-0.3 percent of the nominal dimension, with a minimum tolerance of +/-0.2mm on small features. This is less accurate than injection molded parts produced from hardened steel tooling, which typically achieve +/-0.1mm or better. For most prototype and pre-production applications, vacuum cast accuracy is sufficient for fit, form, and function testing.
What resin should I choose for my vacuum cast parts?
Resin selection depends on the mechanical properties your parts need to simulate. For rigid housings and enclosures, a rigid opaque PU resin simulating ABS is appropriate. For flexible components, a Shore A 40 to 60 flexible resin is used. For transparent parts, a clear PU resin is available. Our engineering team reviews your application requirements and recommends the appropriate resin during the DFM process.
Can you cast parts with metal inserts?
Yes. Metal inserts including threaded brass nuts, stainless steel pins, and electrical contacts can be placed in the silicone mold before casting and encapsulated in the resin during the casting cycle. Insert placement and the minimum surrounding wall thickness are reviewed during the DFM process to confirm that the resin will flow around the insert completely.
When should I use vacuum casting instead of injection molding or 3D printing?
Vacuum casting is the best choice when you need 20 to 100 parts in functional polyurethane resin with a good surface finish, and the lead time and cost of injection mold tooling are not justified at your current quantity. It produces better surface quality and more material options than most 3D printing processes, and it is significantly faster and cheaper than injection mold tooling for small quantities. For quantities above 100 to 500 parts depending on part size and complexity, injection molding typically becomes more economical.
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