Vacuum Casting

What is Vacuum Casting?

Vacuum Casting (VC) is a rapid prototyping process similar to injection moulding suitable for low volume production of plastic parts. Injection moulding uses thermo plastics which are melted and injected in to a metal mould which then hardens and get the shape of the mould.

Similarly, in vacuum casting process thermoset plastics in the form of liquid resin are poured into soft tool made of liquid silicone rubber. The resin is allowed to cure in an oven or under pressure or in room temperature and atmospheric pressure. After curing the resin hardens to the shape which is present in the silicone mould.

The silicone mould is then opened to remove the part. Again, the silicone mould is attached together and the process is repeated. Easily around 20 – 25 parts can be produced from one silicone mould. The parts made in VC process are almost similar to injection moulding parts with similar strength and rigidity. However, the material properties will vary due to the usage of liquid thermoset resin in vacuum casting.  

How Vacuum Casting works?

The process starts by 3D printing the master pattern using DLP / SLA 3D printing technology to replicate all the intricate details present in the design. The 3D printed master pattern is then washed, cured and post processed to achieve the desired finish.

A mould box is made out of foam board and the 3D printed master pattern is suspended into the mould box. A 2-part silicone rubber is mixed thoroughly and degassed in a vacuum chamber. After the degassing, the liquid silicone rubber is poured into the mould box and surrounding the master pattern. The silicone rubber is allowed to cure until it becomes solid. After curing the silicone mould cut in a zig-zig manner and the master part is removed from the mould. This master pattern can be used to make future silicone moulds.

After the silicone mould is made it is time for casting the actual parts. A 2-part urethane resin is taken in required proportions and mixed in a vacuum chamber. The cur silicone mould is joined together and is kept inside the vacuum chamber and connected to the mixing cup. Once the mixing is finished, the urethan resin is poured in the silicone mould. The resin is allowed to cure until its potting time and then the mould is then demoulded and the vacuum casted part is removed from the mould. The part might have flashes & runner which will be removed manually, sanded and painted to achieve the desired finish.

Why Choose Vacuum Casting for your project?

If you are in the process of product development, closing up the design after few iterations with FDM or other 3d printing technologies, and now want a more than a few quantities for proof of concept (POC) or for real time testing, then this is the time when you choose vacuum casting as your prototyping method. Vacuum casting has the ability to make small batches of your part with lesser part per cost than 3D printing technologies.

Still confused if vacuum casting is the right option for your project? Contact our engineer to help you!