Making a silicone prototype is an essential step when you intend to customize and manufacture a product.
The process is a precondition for the manufacturing of complex components and a preliminary assurance of product quality.
In this article, we are going to cover in details the step-by-step process of silicone prototyping.
Manufacturing Process for Silicone Prototype
Silicone prototyping process involves transforming uncured silicone rubber material into a preset shape.
Here are the steps involved in making silicone prototype.
Step 1: Designing of Silicone Prototype
Every product, regardless of the materials used, starts with a design.
Therefore, you should follow basic thermoplastic parts design principles when designing a silicone prototype.
Ensure uniform wall thickness in the silicone prototype design even though silicone rubber does not sink and deform like thermoplastics.
This guarantees even flow of material within the mold during silicone molding process.
You should avoid sharp edges and corners as they could promote a tear when demolding the silicone prototype.
Also, make sure that your design specifications are accurate prior to large scale production of parts. This is because silicone behaves differently compared to other materials.
Step 2: Choosing the Right Method to Make Silicone Prototype
There is need to evaluate the most suitable method for producing the part.
The choice of silicone molding technique to use will depend on the features and complexity of the prototype design.
The common molding techniques used to prototype silicone include:
Silicone 3D Printing
You can now apply 3D printing to make silicone prototypes.
There are advanced elastomeric materials specifically formulated for silicone 3D printers.
Resolution and speed of part fabrication continue to improve whilst the capital cost of silicone 3D printing equipment drops fast.
This is because of rapid advancement in additive manufacturing technologies.
The main advantage of silicone 3D printing is that it does not need mold machining and operates unattended.
Silicone 3D Printing
However, you can face precision challenges when processing fine featured and thin walled silicone prototype designs.
You can produce high-quality silicone prototype castings utilizing non-metallic molds.
Casting is an attractive option because of its low cost and comparatively quick method of making a prototype silicone.
But it is an exceedingly manual operation that needs experience and patience.
Silicone rubber molding is the fastest and cost saving solution when you require prototypes manufactured in small quantities.
You can reuse a single mold tooling for silicone prototyping, which help in saving money and time.
It is easy to reproduce parts without extra tooling or designing.
Some of the common silicone molding techniques you can employ include, compression molding, extrusion molding, injection molding, and transfer molding.
Step 3: Choosing Type of Silicone Prototype Material
Next, you select the right type of silicone rubber to use in the prototyping process.
Choosing the right material during silicone prototype manufacturing is crucial for its success.
Silicone rubber formulation is done to satisfy different application requirements.
Therefore, the two primary material options you will get are:
Heat Cured Rubber (HCR)
Some industries refer to it as solid silicone rubber.
We recommend you apply HCR material in industrial applications, particularly electronic and automotive silicone parts.
It can withstand extremes environments for long.
Liquid Silicone Rubber (LSR)
LSR is an odorless and non-toxic silicone prototype material.
The material is highly biocompatible, implying that it is completely safe for environment and humans.
It is normally the first option for silicone prototypes related to household items like kitchenware and baby products.
You can choose the most suitable silicone material type based on your budget, prototype structure, function, application environment, and safety test requirements.
Injection Molding Liquid Silicone Rubber
Step 4: Making Mold for Silicone Prototyping
We use 3D printing, EDM and CNC machines to size metal molds for silicone prototyping.
The resultant mold complexity and silicone prototype part will help in determining the most appropriate method of mold machining.
Also, you select the right mold material based on your budget, timeline, and expertise of prototype designer.
First, you produce a master model employing the suitable method for mold machining.
You can then make several replicas of the master mold using your material of choice.
It is common practice to utilize steel for production molds and aluminum for prototype molds. However, there is need to consider how fast you would wish to changeover from silicone prototyping to full production.
You can fabricate a production level steel mold where the vital dimensions are changeable after silicone prototype molding and testing.
In addition, this customized mold can process any kind of silicone material.
Generally, polished mold surface makes the silicone part to adhere to the mold tool, leading to prolonged demolding times.
For this reason, we prefer a D2 surface since it is the ideal for successful release of molded silicone prototype.
Step 5: Compounding and Blending of Silicone Material
Silicone compounding describes the complex process of choosing and mixing silicone with additional ingredients.
A proper blend is important to ensure successful molding of silicone prototype.
Silicone raw material is a transparent or milk-white gum-like substance with no strength or elasticity. There is need to compound the raw material with various ingredients to improve its properties and attain desired color.
Some of the ingredients you will add include colorant, accelerator, reinforcing filler, and vulcanizing agent among others.
Step 6: Blanking/Cutting of Silicone Material
After blending, you will collect the silicone rubber material in large rolls protected with a film to prevent dirt or dust.
The material then gets cut into slices using an automatic cutting machine.
The weight of the silicone prototype you intend to mold will determine the width and length of the slices.
Blanking process ensure easier weighing of the material in silicone molding process.
Step 7: Weighing and Placing of Material in Silicone Molding tool
You should cut slices into tiny pieces and weigh them accurately. After this, put them instantly in the tool mold at the right conditions.
Material weight is highly important since excessive material will lead to increase in silicone prototype size.
Similarly, less silicone rubber material will result in a small or missing part.
Step 8: Vulcanization Molding of Silicone Prototype
A vulcanization molding machine is essential in curing the silicone material.
It gets cured under high pressure and temperature to form the prototype silicone.
There are high-precision automatic vacuum vulcanization machines that you can use to create high-performance silicone parts.
This advanced silicone molding machine gives you the capacity and versatility to manufacture quality, high-volume parts within a short time.
Step 9: Demolding of Silicone Part
After fully curing the silicone rubber, the vulcanization molding equipment will disperse the pressure automatically.
Subsequently, it releases the tool mold that consequently opens for you to remove the formed silicone prototype.
You will again place the raw material for the next cycle of vulcanization.
Step 10: Deflashing of Silicone Prototype
Silicone flash describes a papery flap of material that forms at the separation line where the tool mold splits.
The pressured silicone rubber material will stream to every single space of the molding tool.
This is because of the low material viscosity, and high molding pressure when heating and curing the silicone part.
You can minimize flash by using better silicone prototype designs and mold tooling.
It is also crucial to ensure high precision during material weighing for the vulcanization molding stage.
Removing flash is primarily by hands, although you can also employ cryogenic deflashing in some instances.
Flash line will always be present on all silicone prototype parts with a small size of silicone flash remaining.
Therefore, ensure to carefully design and fabricate the molding tool to minimize the parting line, which can affect the silicone prototype appearance.
For additional information on silicone prototyping, kindly reach out to our team of experts.
Pricing and lead time will be dependent on material selection and part complexity.
Contact us today so that we can collaborate to produce your silicone prototypes affordably and efficiently.