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Vacuum Casting: Low-Volume Plastic Parts from Silicone Molds
Vacuum casting is a casting process for plastic parts: a master model, usually 3D-printed, is used to make a silicone mold. Liquid casting resin is then filled into this silicone mold under vacuum, producing parts without air pockets and with a very smooth surface. Depending on the contour, silicone, and casting resin, about 25 castings can be made from one mold.
Vacuum casting thus bridges the gap between 3D printing for single parts and injection molding for large series. You can select vacuum-cast parts in the PROTIQ Marketplace configurator or request them from us.
- approx. 25castings per silicone mold, depending on contour, silicone, and casting resin
- approx. 12 hourscuring time of the silicone mold
- Small seriesbetween 3D printing and injection molding
Process
How does vacuum casting work?
Vacuum casting is a multi-step process: first, a master model is made from the 3D CAD model, then a silicone mold is taken from it, and finally the parts are cast in this mold under vacuum.
- 3D CAD modelThe digital model of the part is the starting point.
- Master modelThe master model is usually made additively, often using stereolithography (SLA), and finished to the required surface quality.
- Silicone moldParting lines, slides, gate, and risers are defined. The master model is suspended in a box and encased in two-component silicone.
- Casting under vacuumLiquid casting resin is drawn into the mold by the vacuum – so no air pockets form.
- DemoldingThe part is removed. After about 25 castings, the mold is worn and is replaced if needed.
Making the silicone mold
After casting, the silicone cures for about 12 hours. The mold is then cut open by hand with a scalpel along the parting line, and the master model is removed. Because the mold is made of flexible silicone, smaller undercuts and pronounced surface textures can also be reproduced.
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Benefits
What are the benefits of vacuum casting?
Vacuum-cast parts come close to injection-molded parts in surface quality and properties – without an expensive steel tool. This makes the process economical for small and medium quantities.
Smooth surfaces
The surface quality is comparable to injection molding – fine details are reproduced as well.
Low mold costs
Silicone molds are significantly cheaper than steel injection molds and quick to make.
Wide range of casting resins
Depending on the resin, hard and rigid, rubber-like, transparent, heat-resistant, or electrostatic dissipative (ESD).
Prototype to small series
Suitable for functional prototypes, pre-series, and small series with production-like properties.
Comparison
Vacuum casting, 3D printing, or injection molding – which fits when?
In terms of quantity, vacuum casting sits between 3D printing and injection molding. Compared to 3D printing, it offers more production-like surfaces and materials; compared to injection molding, significantly lower initial costs.
| 3D printing | Vacuum casting | Injection molding | |
|---|---|---|---|
| Mold / tool | None – directly from 3D data | Silicone mold taken from the master model | Steel tool, high initial costs |
| Typical quantity | Single parts and small series | Small to medium series | Large series |
| Lead time | Short | Master model and mold must be made first | Long due to tool making |
| Design freedom | Very high, including internal structures | Smaller undercuts possible, large ones not | Limited by demoldability |
| Surface | Process-dependent, often post-processed | Very smooth, close to injection molding | Very smooth |
| Materials | Process-specific plastics and metals | Casting resins with a wide range of properties | Production plastics |
Steel injection molds can cost several hundred thousand euros, so injection molding usually only pays off at large quantities. Learn more: Injection molding, 3D printing processes, and CNC machining.
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Applications
What is vacuum casting used for?
Vacuum casting is suitable wherever parts are needed in production-like quality but an injection mold does not yet pay off.
- Functional prototypes and design samples with an injection-molding-like surface, for example for tests or trade shows
- Pre-series and small series, for example until the injection mold is ready
- Housings, covers, and handles with smooth or textured surfaces
- Rubber-like and transparent parts – depending on the casting resin
Learn more about the applications: Prototyping and Series production.
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How do I order vacuum-cast parts?
Upload your CAD model in the PROTIQ Marketplace configurator and select the process – or submit a project request. The following information helps us prepare a suitable offer:
- 3D data of the part, for example as a STEP file
- Quantity and desired delivery date
- Desired material properties, such as hardness, color, transparency, or temperature resistance
- Requirements for surface finish and tolerances
Upload file now Request a project
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FAQ
Frequently asked questions about vacuum casting
What is vacuum casting?
Vacuum casting is a casting process for plastic parts. A master model, usually 3D-printed, is used to make a silicone mold, and liquid casting resin is filled into this mold under vacuum. This produces parts without air pockets and with a very smooth surface.
How many parts can be made with one silicone mold?
Depending on the contour, silicone, and casting resin, about 25 castings. After that, the mold is worn and, if needed, is replaced by a new mold that can be taken from the same master model.
What quantities is vacuum casting suitable for?
For low quantities, small series, and medium-sized series. For single parts, 3D printing is usually faster; for large series, injection molding is more economical.
What is the difference between vacuum casting and injection molding?
In injection molding, plastic is injected into a steel tool, which causes high initial costs and only pays off at large quantities. In vacuum casting, casting resin is filled into an inexpensive silicone mold – ideal for small and medium quantities.
What is the difference between vacuum casting and 3D printing?
3D printing produces parts directly from 3D data, without a mold, and offers the greatest design freedom. Vacuum casting requires a mold but delivers very smooth surfaces and a wide range of casting resins with production-like properties.
What material properties are possible with vacuum casting?
Depending on the casting resin, parts can be hard and rigid, rubber-like, transparent, heat-resistant, or electrostatic dissipative (ESD).
Are undercuts possible with vacuum casting?
Smaller undercuts and pronounced surface textures are possible because the silicone mold is flexible. Large undercuts, however, limit demolding.
How do I order vacuum-cast parts from PROTIQ?
Upload your CAD model in the PROTIQ Marketplace configurator and select the process, or submit a project request. If you have questions about material, quantity, or surface finish, we will be happy to advise you personally.
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