Vacuum Casting: A Quick Guide

Table of Contents

What is Vacuum casting?

vacuum casting

Vacuum Casting (also known as Polyurethane casting) refers to the use of existing parts to make silicone molds in a vacuum state. Polyurethane, silica gel, nylon, ABS and other materials are used for casting in a vacuum state, so as to clone the same replica as the original part.

Normally, only 10-12 replicas can be produced per set of silicone molds. Suitable for making new products below 100 sets. Therefore, vacuum casting prototype is fundamentally different from mass production of plastic injection parts. For mass production, injection molds need to be manufactured. Prototype is to examine the appearance and structural properties of products, so that designers can understand the feasibility of mass production of products and avoid the risk of directly manufacturing molds.

Vacuum casting features:

No need to make molds, low processing cost, short production cycle, high simulation degree, suitable for small batch production and other characteristics. Polyurethane casting can speed up R&D progress and avoid unnecessary waste of money and time during R&D.

Demand market of vacuum casting

Vacuum casting is often used to make prototypes in the Rapid Prototyping industry. Vacuum casting is also the first choice for making small batches of prototypes before making molds. Many industrial products, such as auto parts, robots, medical equipment, and 3C products, develop from a concept or idea to a mature mass-produced product, requiring designers and developers to continuously find problems and improve product planning.

Manufacturing molds is expensive and takes a long time.What makes the planning and developers more difficult is that if the planning is wrong, it will cause a lot of unnecessary losses.Because it takes tens of thousands of dollars to make a set of steel molds. Therefore, before making molds, small batches of Polyurethane casting prototypes will be a good way to check whether new products are qualified or not, and can also prevent unnecessary losses.

vacuum casting 2

How many times can the silicone mold be used?


Depending on the complexity and size of the part, the materials used vary. About 10-20 times.

What materials can Polyurethane casting simulate?

There are many types of Polyurethane materials. Various plastics can be simulated.

Common materials are ABS, PC, PP, PMMA, nylon, silicone, soft rubber and other materials.

Application of Vacuum Casting


1. Plastic prototype: its raw material is plastic, mainly the prototype of some plastic products, such as robots, medical equipment, televisions, monitors, telephones, etc. The most common photosensitive resin in 3D prototype proofing is plastic prototype.
2. Silicone lamination prototype: its raw material is silicone, which is mainly used to display the shape of product design, such as automobiles, mobile phones, toys, handicrafts, daily necessities and so on.

transparent vacuum casting

Advantages of Vacuum Casting

Silicone casting has many advantages. The advantages are fast time, low cost, and low probability of processing failure. More than 20 identical products can be made using one silicone mold. Greatly reduces product development costs, cycles and risks.

  1. Low production cost. The processing cost is much lower than CNC machining and 3D printing;
  2. The production cycle is short. Save the time of making molds and greatly improve production efficiency;
  3. Save the time of making molds, gain valuable time for customers to develop new products, and seize the market standby;
  4. Suitable for small batch production (within 1000 pieces), with short customization time and low cost;

Disadvantage of Vacuum Casting

  1. The material of Vacuum Casting is mixed and solidified by 2-3 groups of liquids, and the material properties cannot be compared with CNC;
  2. The form of vacuum casting has a certain degree of similarity with injection molding, and has a certain shrinkage rate. The thicker the workpiece and the larger the workpiece shrinkage will be more obvious. Taking a workpiece with a volume of 100mm as an example, the general shrinkage rate is 0.25%;
  3. Casted products can not withstand too high temperature, generally it is easy to deform when baked above 50 degrees Celsius. Therefore, whether to use vacuum casting to replace CNC processing should be determined according to the function of the prototype. Not all products with multiple sets are suitable for vacuum casting.

Silicone mold making process

1. Prototyping
Before making a silicone replica hand model, you need to make a master pattern. It can be 3D printed or CNC made.
2. Silicone mold
After the master pattern is ready, start making the silicone mold.
After eight hours of drying, the silicone die was cut open and the master pattern was taken out. The silicone mold is now ready.
3. Injection type
The liquid gum material is poured into the silicone mold and dried. The service life of the transparent silicone mold is about 15-25 molds. Suitable for small batch customization

Which products are suitable for vacuum casting:

Personalized products, the demand is small, the structure is more complex, and it is not cost-effective to open traditional steel molds, such as auto parts, robots, medical equipment, 3C electronic products.

The cost of vacuum casting:

The cost of vacuum casting is generally determined by product size, product structure, material and surface finishing

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