Vacuum Casting

Vacuum Casting is a vital element of professional rapid prototyping services and low volume production. It is a very cost-effective and efficient manufacturing process, small batches high quality similar injection molding parts are made within several days.

Vacuum casting is a fast & cost-effective ways of producing a small quantities of high quality rapid prototyping parts. What are vacuum casting processes?

• Step 1, Create a mater model

The first step is to make a perfect master model, which is usually created from 3D printing using SLA technologies, some times also made by CNC machining, and polish the surface to the required standard. Texture surface can be done by painting or spraying sanding on the master model. It is important to note that the master sample can withstand temperature up to 40°C.

• Step 2, Make the silicone mold

Firstly, Suspend the prepared master model into the casting case.

Then carefully pour the silicone into the casting case, in which the silicone flow inside and completely fill every features of the master model. This process is done in a vacuum chamber to remove the air from the silicone and ensure there are no bubbles mould's surface finish.

Once the case is completely filled and the master model is covered by a layer of silicone, the mould is then put into the oven to curve the silicone for around 8-16 hours, depend on the size of the mold.

After the mold is curved, carefully split the mold with a knife, remove the master model out of the mold, and inspect the mould.

• Step 3, Pour Polyurethane resin

After mold is assembled and casting funnel is inserted, the mold is taken back to the vacuum chamber. Pour the prepared liquid polyurethane into the silicone mold through the funnel. The vacuum remove the air/gas out of the polyurethane to ensure all details are molded and to avoid the blemish, air bubble on the surface finish. After pouring, the mould is heated to cure the polyurethane under 70-80°C temperature in the heating chamber.

• Step 4. De-mould the cast part

After the cured polyurethane has cooled, open the mould, and remove out the cast part. Then cut off the gate and the risers, and trim and clean the parts, then do inspection and surface finishing. The vacuum casting is finished, the product is ready to used. Generally, the lifespan of the vacuum casting mold is 15-20 shots.

Both CNC machining prototype service and vacuum casting service are ways to produce rapid prototypes. CNC machining refers to programming by CNC machining language. The cutter on the CNC equipment moves on the material according to the path set by the program, and cuts off excess material to obtain the prototypes of required shapes and sizes. Vacuum casting refers to making simple silicone molds through master patterns, and then replicating the parts. The cost of vacuum casting is low and the cycle is short. So what are the main difference between CNC prototyping and vacuum casting prototyping? Let's take a look below:

• Materials are Different

The materials of CNC prototypes are extensive and can include plastic and metal. Plastic CNC prototyping materials include: ABS, acrylic, PP, PC, POM, nylon, PEI, PEEK, PBT, PTFE and other materials; Metal CNC prototyping materials include: aluminum, stainless steel, copper, steel, iron, etc. The range of materials used for vacuum casting prototypes is relatively narrow, mainly rubber, ABS, PC, PA, PP, and acrylic materials, etc.

• The Precision is Different

The precision of CNC machining prototypes will be much higher than the precision of vacuum casting prototypes. The precision of our CNC machining is generally between 0.02mm-0.05mm, while vacuum casting prototypes may be slightly deformed and shrunk due to thermal expansion and contraction, the accuracy is not so easy to control, generally is around 0.2mm. Therefore, in general, vacuum casting prototype does not have very strict requirements on precision.

• The Production Speed is Different

CNC machining requires machining step by step, while vacuum casting only needs to make a silicone mold and then replicate the component. Generally, a silicone mold can replicate about 8-15 parts, and the production speed is faster than CNC machining.

• The Cost is Different

Since the CNC machining prototyping needs to be machined step by step, and it takes a certain amount of time to adjust the machine, the cost of the CNC prototype is generally relatively high, while the vacuum casting prototyping can be one-piece forming produced via vacuum mold casting. Therefore, the production cost of Vacuum Casting will be much lower.

When comparing polyurethane vacuum casting to 3D printing during the rapid prototyping stage, vacuum casting holds several distinct advantages, particularly for specific project needs:

1. Superior Material Properties

Vacuum casting uses urethane materials that closely mimic injection-molded plastics, offering better strength, flexibility, and heat resistance than most 3D-printed materials.

This makes it ideal for functional testing and creating end-use prototypes that need to perform under real-world conditions.

2. Higher-Quality Surface Finish

Vacuum-cast parts have a smoother, refined surface directly out of the mold, without visible layer lines common in 3D-printed parts.

In contrast, 3D printing often requires additional post-processing (e.g., sanding or coating) to achieve comparable finishes.

3. Color and Texture Options

Vacuum casting offers a wide range of colors and textures directly from the mold, reducing the need for secondary finishing steps.

This makes it particularly useful for creating realistic prototypes with precise aesthetic features.

4. Efficiency for Small- to Medium-Batch Production

While 3D printing excels in producing one-off prototypes, vacuum casting is more cost-effective and time-efficient for small to medium production runs, as each silicone mold can produce multiple identical parts.

5. Increased Durability

Vacuum-cast urethane parts are typically more robust and long-lasting, making them better suited for rigorous testing.

• Our vacuum casting prototyping manufacturing cost is low and production time is short.

• Cost effective for Low volume production. After making a master pattern and the silicone mold, it can be duplicated according to the master pattern.

• Flexible de-mould operation. After the mold is dry and solidified, the mold is soft and flexible, conductive to cutting and de-mould.

• Diverse material and colors for your choosing.

• High quality. The defect rate is small. As long as there is no defect on the master pattern, the vacuum casting parts will not be wrong. Most of the time we have avoided it.

• Good repeatability, ensure same quality and consistency.

1. Prototyping for Functional Testing

Vacuum casting is widely used to create prototypes that closely mimic the final product. These prototypes can be used for functional testing, design validation, or marketing presentations.

2. Low-Volume Production

For products that do not require mass production, vacuum casting offers an efficient solution. It is ideal for small production runs of up to 20–50 units, providing high precision and excellent surface finishes.

3. Customized and Complex Components

The process allows for the production of intricate designs and customized components, making it valuable in industries like aerospace, automotive, and healthcare, where bespoke parts are needed.

4. Consumer Goods and Electronics

Vacuum casting is frequently used to produce housings, panels, and other parts for consumer goods and electronic devices. It provides cost-effective solutions for small batches of high-quality items.

5. Medical Equipment Prototyping

In the healthcare sector, vacuum casting is employed to prototype medical devices, ensuring they meet functional and ergonomic requirements before mass production.