VACUUM CASTING - URETHANE CASTING

Author: zhongzhu

2023-05-10

Vacuum Casting - Urethane Casting

Zhongzhu is fully capable of handling your vacuum casting and silicone molding needs. With years of expertise in the field, we can fabricate your plastic parts to the highest standard, as well as cost-efficient and with fast turnarounds.

Vacuum casting is a great method to make rigid or flexible parts, and is ideal for high quality prototypes, function testing, concept proofing and display demos. Urethane casting parts can be made from a few to hundreds as required.

Advantages of Vacuum Casting

1 Fast turnaround

Zhongzhu can provide up to 20 parts in 15 days or less, depending on part specification and volume.

2 Affordability

Silicone molds are less expensive than the tooling used for injection molding, resulting in low prices.

3 Capable of producing large parts

Depending on the type of equipment used, vacuum casting can to create very large parts.

4 Superior surface finish to injection molding

The vacuum process removes air bubbles and allows the material to capture fine details.

5 Color options

Coloring pigments can be added to the resin for a variety of color options.

6 Repeatability

Silicone molds can be used around 20 times before they need replacing.

What is

Vacuum Casting?

Vacuum casting is a manufacturing technology that uses a vacuum to draw liquid casting material into a mold. It differs significantly from injection molding, which pushes liquid material into a mold using a screw.

The process of vacuum casting offers significant advantages, and is particularly useful for parts that have undercuts or fine details.

The process starts with a master model, which Zhongzhu 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.

Once it has been cut and the master model removed, the silicone mold can be put to use. 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 Process

Step 1: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.
Step 2: Mold making	Casting molds are made from liquid silicone. Half-Fill the casting box with liquid silicone, Heat the casting box until silicone is fully cured and then allowed to cure in an oven for 16 hours. Fill with extra silicone liquid which is also heated & cured. Once dried, the mold is cut open and the master removed.
Step 3: 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.
Accurate	± 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.