silicone prototyping,vacuum casting

Vacuum Casting

Based on the silicone mold made from a product prototype (master), vacuum casting or urethane casting produces the same parts in the vacuum environment using polyurethane (PU) materials with similar properties to ABS, PC, PMMA, soft rubber, and more. The parts possess the same strength and hardness as mass production products, even with the colors required. With its replicability, vacuum casting is not only for producing prototypes but also low volume production of plastic and soft rubber products.

Our silicone prototyping technicians carefully control all operational parameters: from mixing, de-bubbling, stirring, preheating, and injection, to the solidification of the PU material and rubber, thus guaranteeing minimal shrinkage and fine details. At X Rapid Technologies, silicone prototyping parts made by vacuum casting show accurate part replication and consistent mechanical properties. They can be deliverable within a short lead time. 

Advantages of vacuum casting

·  Low cost and relatively short product production cycle. Less waste of material. The processing cost is also much lower than CNC machining and 3D printing.

·  Suitable for short-run production. After making a master, it can be copied via silicone mold very rapidly, while CNC machining can only manufacture parts one at a time.

·  Easy molding process. Cured soft silicone molds are transparent or translucent, have good tensile strength, and are easy to cut and separate.

·  Small chance of processing failure. Reproduction is unlikely to go wrong if the master is in order.

·  Good repeatability. A mold made of silicone has good fluidity before curing, and after vacuum de-bubbling, the part retains its detailed features.

Disadvantages of vacuum casting

·  There is a possibility of deformation due to shrinkage. Silicone prototyping parts shrink after cooling following high-temperature heating, resulting in deformation.

·  Not resistant to high temperatures, the silicone prototyping parts can generally only withstand a high temperature of about 60 degrees centigrade.

·  The strength and hardness of the silicone prototyping parts are lower than that of CNC machined ones.

Vacuum casting working processes

1.  Make the master part via CNC machining or SLA 3D printing.

2.  Enclose the master part with wooden boards, preparing for making the silicone mold.

3.  Pour the liquid silicone, which has been vacuumed with a vacuum machine, to cover the master. 

4.  Bake it in the oven to accelerate the curing of the silicone mold.

5.  Take the master part out of the silicone mold.

6.  Vacuum and pour the raw material to make a copy of the master part.

7.  Demold and take out the copied part.

8.  Finishing as required.

When do I need vacuum casting?

Consider the materials and quantities for rapid prototyping manufacturing. Vacuum casting can only make plastic and soft rubber parts. Vacuum casting is not the most economical option when the quantity is very low, such as 1 piece. Because we need to make a master via CNC machining or 3D printing to make the silicone mold. And one silicone mold lasts 15-20 shots. The more you produce, the more costs of silicone mold you can offset.

Get an instant vacuum casting quote
silicone prototyping,vacuum casting
High Efficiency

15 - 20 parts can be produced by one silicone mold, which shortens the lead time.

silicone prototyping,vacuum casting

Most silicone prototyping parts can be formed integrally in one piece with good strength.

silicone prototyping,vacuum casting
Varied Materials

Besides manufacturing different plastic parts, vacuum casting can also make soft rubber silicone prototyping parts.

Material Options

Different PU series, similar to ABS, PC, PMMA, PP, POM, soft rubber, etc

Highest Tolerances


Vacuum Casting FAQs

For plastic prototypes by vacuum casting, the finishings can be de-burring, polishing (PMMA-like parts), painting, electroplating, laser engraving, silk screening, etc. All those surface treatments available for plastic parts can be done to vacuum-cast plastic prototypes.

There is no MOQ for X Rapid Technologies. As a prototype creator, we offer one-off prototypes and small-batch production. However, vacuum casting is more cost-effective when the quantity is about or more than 5 pieces. Don’t worry. We will help you make the choice based on your certain requirements.

Compared to CNC machining and 3D printing, vacuum casting usually takes longer. Because it involves the process of making the silicone mold. As a prototype creator offering custom rapid prototyping services, we will calculate the specific lead time for each project during the quotation period. In case you want to make it faster, be sure to let us know.

For silicone prototyping, please send us files in CAD, STP, STEP, IGS, or X_T format.

Sure. You can take a look at our previous vacuum casting cases on our Case Studies page. For more pictures of silicone prototyping parts, you are welcome to contact your 1-on-1 project manager.