What is Vacuum Casting? And How Vacuum Casting Benefits


Vacuum casting is a manufacturing technique that involves drawing liquid casting material into a mold using a vacuum. It differs significantly from injection molding, which pushes liquid material into a mold using a screw. The process of vacuum casting services offers significant advantages, and is particularly useful for parts that have undercuts or fine details. The process starts with a master model, which 3ERP creates using one of its CNC machining centers — though 3D printing can also be used. This master model is then immersed in liquid silicone, which is cured and becomes the mold. The silicone mold can be used when it has been cut and the master model has been removed. This stage involves pouring casting resin into the mold, as the vacuum removes bubbles and air pockets to ensure a smooth finish. The resin part is then cured in an oven and removed from the silicone mold after cool down, which can be reused around 20 times. Each cast part is an exact copy of the original master model. It’s a perfect solution for rapid prototyping and making small batches of quality parts.

Vacuum casting, sometimes referred as Urethane casting or Polyurethane casting uses silicone moulds to make plastic and rubber components under vacuum. It is an extremely adaptable manufacturing process capable of mimicking the injection moulding to produce complex parts in polyurethane resins and cast nylon.

Master building

Masters are 3D solids of your CAD designs. They are usually made by CNC machining or with 3D Printing. Making Master in 40° temperature. After finish and inspect the masters, we will move to silicone mold making.

Mold making

Liquid silicone is used to make casting molds. Fill the casting box halfway with liquid silicone, heat until the silicone is fully set, and then cure for 16 hours in the oven. Fill with additional silicone liquid that has been heated and hardened. The mold is sliced open and the master is removed once it has cured.

Make the parts

Poured the casting resins into the empty cavity to create a highly accurate copy of the original. It’s even possible to overmold with two or more materials. Silicone molds are typically good for 20 or so copies of the master pattern.

Vacuum Casting Technical Specifications

Typical lead time

Up to 20 parts in 15 days or less, depends on the part specification and volumes.


± 0.3% (with lower limit on ± 0.3 mm on dimensions smaller than 100 mm)

Minimum wall thickness

To ensure that the mold is filled properly, a wall thickness of at least 0.75 mm is necessary. For best results, we recommend a wall thickness of at least 1.5 mm

Maximum part dimensions

The size of the mold is limited by the dimensions of the vacuum chamber (1900 x 900 x 750 mm) and by the volume of the product (maximum volume: 10 liters)

Typical quantities

Up to 25 copies per mold (depending on the mold’s complexity and the casting materials)

Color & Finishing

Pigment is added to the liquid polyurethane prior to casting, custom painting and texture.

Characteristics & applications of vacuum casting

  • Vacuum casting is one of the most cost-effective ways to produce high quality, low volume plastic parts which can be similar to injection moulding parts
  • The parts are especially suitable for form, fit and function tests during the embodiment design stages, where it can be used for marketing, field user testing and product design verification purposes
  • There are a variety of vacuum casting resins on the market that may be used to make parts that meet a variety of design requirements, including temperature requirements, varied surface textures, hardness, and so on
  • There are a variety of vacuum casting resins on the market that may be used to make parts that meet a variety of design requirements, including temperature, surface texture, hardness, and so on.
  • Sometimes high-quality wax masters can be made using vacuum casting for investment casting to increase the finer details of intricate features

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