How to Make a Silicone Mold for Rapid Prototyping

Rapid prototyping projects prove concepts and prepare the stage for the product to enter the mass manufacturing phase. Silicone molds are a preferred production choice for low and high-volume applications, making them an in-demand manufacturing method and widely available from many manufacturing partners in countries around the globe.

A mold is a shaped cavity featuring design and construction with many different materials, from tool steel to silicone. Silicone is a group of polymers featuring siloxane, sometimes used in the manufacturing of consumer products like contact lenses, gaskets, and protective cases.

While a silicone mold tool isn’t as durable as one made from aluminum, it’s more affordable and easier to produce. These characteristics of silicone molds make them ideal for rapid prototyping projects.

The flexibility of silicone molds and the mechanical and adhesive properties of the material, being that few materials stick to it, make it easy to remove finished components from the mold.

Silicone molds are the better choice for low-volume projects and prototyping due to the lower cost of producing these molds compared to using materials like tool steel. Typically, a silicone mold proves the concept, and the customer informs the manufacturing partner to move to tool steel or aluminum tooling after proving concept and gaining market demand for mass production.

However, silicone molds can be beneficial for other manufacturing processes, such as vacuum casting. This process involves the manufacturer filling a mold with polyurethane materials in a pressurized vacuum environment. The process is highly reliable, producing consistent parts.

Vacuum casting is ideal for low-volume production and small batches and is the more affordable option compared to injection molding for smaller quantities. A silicone mold used in vacuum casting processes has a service life of approximately 20 castings before it’s compromised.

Wax casting often implements silicone molding in designing and constructing industrial components and jewelry. In wax casting or “investment casting”, manufacturers fill silicone molds with melted wax to create the master pattern.

These models are coated with ceramic before being fired in a kiln. The remaining ceramic is used as the new mold and handles the pouring of molten metals to form components. Typically, manufacturing professional silicone molds requires the use of specialist vacuum casting machines and kilns for silicone curing.

How To Manufacture a Master Pattern

The master pattern defines the final properties of silicone parts. Therefore, it’s vital for manufacturers to make or obtain a detailed, high-quality pattern that’s easy to mold.

The pattern should have a long service life, especially if the manufacturer plans to produce several silicone molds from it in the future. They’ll also need multiple molds in vacuum casting applications, so the pattern must be durable.

The most common manufacturing methods for producing master patterns.

3D Printing for Master Patterns

The implementation of CAD technology and its integration into production methods makes pattern manufacturing much easier and cost-efficient. It’s also more accessible to non-specialists who want to create DIY prototypes.

High-quality 3D printers create smooth surfaces on finished parts. So, these properties make it the ideal choice for building master patterns.

Pros:

Requires the use of digital files to design and execute the project.
Repeatable, accurate results.
Printers don’t need an industrial setting for manufacturing small batch masters.
Low post-processing requirements when using SLA technology.

Cons:

Expensive devices for a one-off project.
Tolerances aren’t as tight as other methods.
Brittle resins used in the process lead to short service life.

CNC Machining for Master Patterns

CNC machining is another common manufacturing method for producing silicone mold master patterns. With this method, the manufacturer can use materials like tool steel or aluminum to build the master pattern.

The result is a long-lasting pattern suitable for mass-production purposes. You get a long service life and repeatable quality. However, the downside is that these molds are much more expensive than alternatives. It’s the better choice for projects where the prototype and concept are proven, and the manufacturer is setting up to move into the mass production phase.

CNC machines can produce highly intricate patterns and can cut and shape a wide range of materials, from metal to plastics and composites, with very tight tolerances.

Pros:

Accurate and precise master patterns.
Suitable for high-volume mass production projects.
Suitable for use after proving concept and prototype.
Compatible with heat-resistant material.
Long service life.

Cons:

The most expensive option for creating a master pattern.
Inaccessible to some smaller companies.
Components may require post-processing.

The Process of Manufacturing a Silicone Mold

Manufacturers can produce the silicon mold themselves if they have the right tooling setup and skills on hand to complete the project. However, many will choose to outsource the project to specialists with strict instructions on prototypes.

The master is the most important component of the silicone molding process. If it’s not completed correctly, the final product will be defective.

The project’s demands, whether for rapid prototyping purposes or mass production, determine the materials required for the master.

The materials used in the production of the master determine the technology required to make it and the costs involved with the project.

After receiving the completed master, the manufacturer follows this step-by-step process to manufacture the silicone mold for prototyping or mass production purposes.

Step #1 – Lay the master pattern and prepare it for materials.
Step #2 – Mix and add the silicone to the master.
Step #3 – Remove the silicone mold after it finishes curing.
Step #4 – Remove the master pattern.
Step #5 – Cast your prototype components.

In Closing

There are several ways to manufacture silicone molds. The bulk of the decision on which process to use depends on whether you’re looking at a small batch project or the eventual shift into mass production. Consider your needs carefully in the planning phase of your project to avoid disappointment and increased costs.

There are significant cost differences in silicon molds made with 3D printers or CNC machines, and you’ll need to consider your project requirements and budget to select the right process. Consult with an experienced manufacturing professional to get the advice you need on making silicone molds for your projects.