Vacuum Casting Services
We offer vacuum casting services, suitable for rapid prototyping and low-volume production, supporting various resin materials, achieving fine details and stable performance.
What is Vacuum Casting?
Vacuum casting, also called urethane casting or polyurethane casting, is a low-volume manufacturing process used to produce plastic prototype parts from silicone molds. A master pattern is usually made by CNC machining or SLA 3D printing, then copied into a silicone mold for repeated resin casting under vacuum.
The process is often used when a project needs 10 to 50 plastic parts with injection-mold-like appearance, good surface detail, and faster tooling than traditional steel molds.
Advantages of Vacuum Casting
Silicone molds at low cost: an economical solution for small batch production
Vacuum casting uses silicone molds to replace traditional metal molds, and the cost of a single set of molds can be reduced by about 60%-80%. Silicone molds can be made within 24-48 hours through the master mold turning technology, and a single set of molds can be repetitively poured 20-50 times to meet the needs of small and medium batches of up to 50 pieces. Compared with steel mold development, which requires 3-8 weeks and tens of thousands of dollars of investment, this process significantly reduces the capital and time thresholds for prototype verification and trial production.
Fast delivery: 10-15 days from design to functional part
By integrating digital modeling and rapid tooling technology, vacuum casting achieves extremely fast response in the whole process:
3D data import → master mold making: 3-5 days (with light-curing 3D printing or CNC machining)
Silicone mold curing: 12-24 hours
Polyurethane casting and post-treatment: 2-3 days
Under strict quality control, up to 50 mechanically compliant parts can be delivered in 10-15 working days, which is a 70% compression of the traditional molding cycle time.
High precision and detail reproduction: ±0.1mm tolerance and microstructure reproduction capability.
Vacuum environment combined with pressure infusion process can be achieved:
Dimensional accuracy: ISO 2768-mK grade, ±0.1mm/m control of critical dimensions.
Microscopic features: clear reproduction of 0.2mm fine texture, 0.15mm sharp edges and 0.05mm depth of etched markings.
Wall thickness adaptability: Stable realization of 0.8-15mm wall thickness structure, thin-walled areas filled with integrity> 98%
Surface finish advantage: Ra 0.4-0.8μm grade native texture
Compare surface quality data for different processes:
Let’s compare the numbers
| Process Type | Typical Ra value (μm) | Post-processing requirements |
|---|---|---|
| Vacuum Casting | 0.4-0.8 | Can be directly painted/electroplated |
| SLA 3D Printing | 1.2-2.5 | Sanding + Primer |
| CNC machining | 1.6-3.2 | Fine milling + polishing takes 2-4 hours |
| FDM 3D Printing | 8-15 | Unable to meet Class A surface requirements |
| Urethane castings can present a surface effect similar to injection molding parts by virtue of vacuum degassing and mold high-gloss replication capabilities, reducing secondary processing costs. |
Multiple material options: Performance covering system of engineering grade resin
Six categories of material properties customization of polyurethane resin library for vacuum casting:
| Feature Type | Typical parameters | Application scenario examples |
|---|---|---|
| Flexible elastomer | Shore A 30-90, elongation at break 500% | Seals, cushions |
| Rigid structural material | Flexural strength 120MPa, HDT 160℃ | Gears, housing components |
| Transparent optical grade | Transmittance 92%, haze <1% | Lens and lampshade prototypes |
| High temperature resistant type | Continuous temperature resistance 180℃, peak temperature 220℃ | Engine peripheral non-metallic parts |
| Imitation metal texture | Aluminum powder/copper powder filling, Ra＜0.6μm | High-end decorative parts, home appliance panels |
| Flame retardant certification | UL94 V-0, GWIT 775℃ | Insulation parts for electrical equipment |
Vacuum Casting services
Suitable for small batches of plastic prototype production parts processing
Detailed technical analysis of the working principle of vacuum casting, three steps (master mold, making silicone mold, casting process)
Master mold making
Function: The master mold is the original model for casting, which determines the shape, details and precision of the final product.
Production method:
3D printing (such as light-curing SLA): suitable for complex curved surfaces, with an accuracy of ±0.1mm.
CNC machining (metal or engineering plastics): suitable for high-hardness, high-precision master molds.
Physical reproduction: Reverse generation of digital models through 3D scanning of existing parts.
Requirements:
The surface needs to be highly polished (such as mirror effect) or retain specific textures (such as frosting, biting).
Spraying release agent (such as polyvinyl alcohol solution) to facilitate subsequent silicone mold separation.
Silicone mold making
Process direction:
Pouring silicone: Wrap the master mold with liquid silicone to form an enveloping layer.
Vacuuming: Use a vacuum machine to suck out the bubbles in the silicone to avoid internal defects in the mold.
Heating and curing: The silicone hardens at 40-60°C to form an elastic mold.
Cutting and parting: Cut the silicone along the parting line, take out the master mold, and the mold cavity is formed.
Core advantages of silicone molds:
Low cost: The cost of a single set of silicone molds is only 10%-20% of that of metal molds.
Fast speed: It can be completed in 1-2 days and can be reused 20-50 times.
Strong adaptability: It can replicate 0.1mm fine textures (such as logos and fine lines).
Casting process
Resin preparation:
Select two-component polyurethane resin and mix in proportion (such as 100:30).
Pre-vacuum to remove bubbles in the resin (to avoid internal pores in the finished product).
Vacuum infusion:
Put the silicone mold into a vacuum box and pump to negative pressure (about -0.09MPa).
Pour the resin and use the pressure difference to fill every corner of the mold with the resin.
Curing and demoulding:
Heat to accelerate curing (such as 60℃/2 hours), and the resin hardens and forms.
Disassemble the silicone mold, take out the casting, and trim the burrs to get the finished product.
Let's summarize the points mentioned above
Why is vacuum needed?
There are three reasons, namely:
Eliminate bubbles: The vacuum environment expels air from the mold and resin to avoid pores and material shortages in the casting.
Improve filling: Negative pressure makes the resin “sucked” into the mold, ensuring that complex structures (such as thin walls and deep grooves) are completely filled.
Surface finish: Without bubble interference, the casting surface can directly reach Ra 0.4-0.8μm (close to the level of injection molded parts).
Summary:
For small batches of plastic parts, vacuum casting offers a practical balance of tooling cost, lead time, surface quality, and design flexibility before a project moves into injection molding or other production methods.
Vacuum Casting vs other processes
| Technology | Advantages | Limitations | Applicable scenarios |
|---|---|---|---|
| Vacuum Casting | Low cost (silicone mold), high surface finish | Short mold life (<50 times) | High precision small batch within 50 pieces |
| 3D Printing | No mold required, complex structures can be freely formed | Rough surface, low strength | 1-5 pieces of verification, non-functional parts |
| Traditional injection molding | Low cost and high efficiency in large quantities | Steel mold development is expensive (50,000+) and takes a long time (1-2 months) | Mass production of more than 10,000 pieces |
Vacuum Casting FAQ
Increase the vacuum degree to above -0.095MPa, and pre-vacuum for about 5 minutes after the resin is mixed.
When designing the master mold, enlarge the size according to the resin shrinkage rate (such as a scaling factor of 1.003) and control the workshop temperature at 23±2℃.
Control the mold temperature fluctuation to less than ±2°C, and enlarge the size of the master mold according to the resin shrinkage rate when designing (such as a scaling factor of 1.003).
Is vacuum casting suitable for low-volume production?
Yes. Vacuum casting is commonly used for low-volume plastic parts, prototype housings, appearance models, and functional samples when steel injection molds are not yet cost-effective.