Silicone rubber tools are widely used in various industries. Understanding the silicone rubber tooling technology can help you control product quality and production costs. This article will introduce you to the technology steps and applications. We hope it can help you efficiently meet customers’ customized requirements and enhance your core competitiveness.
Basic Knowledge of Silicone Rubber Tooling Technology
Silicone rubber tooling is one form of indirect Rapid Tooling (RT) technology used for prototype and low-volume production. Its main value lies in significantly reducing your manufacturing costs and shortening the development cycle, as well as enhancing your supply efficiency.
If you want to use this technology, we highly recommend that you apply it to new product development and small-scale production. This way, you avoid the high expenses of large-scale steel molds and can flexibly control the production schedule of the project.
Green Manufacturing (GM)
Green Manufacturing (GM) is defined as supporting and maintaining a sustainable production method. You can interpret it as not damaging the environment while producing products or services.
In addition to meeting the social and technical elements that take into account the design, it is also necessary to ensure the safety of employees and the full life cycle use of products. This is Environmental Conscious Design and Manufacturing (ECD&M).
If you want to incorporate such a concept, you need to coordinate the production process, management departments, and all personnel, and minimize resource input and various production waste to the greatest extent.
Rapid Tooling (RT)
In addition to meeting the requirements of GM, you also need to shorten the time for developing new products as much as possible. Generally speaking, to achieve this, you need Rapid Tooling (RT) technology.
RT is an extension of Rapid Prototyping (RP), meaning that your molds need to meet the performance requirements of the final product. And RT can be divided into two types: direct and indirect.
- Direct RT: When you use Direct RT to produce products, direct fabrication of production tooling by additive manufacturing, which can improve the accuracy of your parts.
- Indirect RT: If you use Indirect RT, rapid prototyping is used to create patterns that are then converted into molds. Moreover, Indirect RT can be broadly categorized into soft tooling, which typically employs silicone rubber, and hard tooling, which utilizes materials such as epoxy resin filled with aluminum particles or low-melting-point metals.
You can manufacture complex geometries by replacing the traditional steel molds with silicone rubber molds, ensuring high product accuracy while maintaining production efficiency.
Steps of Silicone Rubber Tooling Technology
Design of Master Mold Pattern
The design of the mold directly determines the quality of your final product and the production cost, and can help you stand out from your competitors. 3D printing (3DP), stereolithography (SLA), and laser sintering are popular prototyping technologies.
First, you need to create a pattern and use CAD software to edit the model. Then, use layer slicing to generate two-dimensional drawings from the three-dimensional model. Next, you select the most suitable technology to produce the pattern.
However, since silicone rubber will completely replicate its shape and surface, you need to optimize the pattern surface during the design process. Moreover, the master pattern should have a smooth surface and sufficient surface energy to ensure proper wetting of the pattern surface and accurate replication of details.
Casting Silicone Rubber
Casting is the crucial step in turning the pattern model into reality, so choosing the right silicone rubber material is very important. Silicone rubber has heat resistance, flexibility and dimensional stability., which is the main reason why it can be used as a mold material.
We recommend that you use Liquid Silicone Rubber (LSR) or RTV-2 (Room Temperature Vulcanization) silicone rubber as the material. The main types of cured silicone rubber include platinum curing and peroxide curing. You can refer to the following table for comparison and selection:
| Comparison | Platinum-Cured | Peroxide-Cured |
| Clarity and Transparency | High transparency | Semi-transparent to opaque, whitish or yellowish appearance with poor light transmission |
| By-products and Extractables | Addition reaction generates no by-products; extremely low extractables, odorless and tasteless | Produces organic by-products such as benzene derivatives and ketones; has odor with risk of extractable migration |
| Tensile Strength | Generally high tensile strength with well-ordered molecular chains after curing, delivering outstanding mechanical performance | Generally superior baseline mechanical strength |
| Resilience and Compression Set | Excellent resilience and low compression set, maintaining stable sealing performance over long-term use | Relatively low crosslink density; inferior long-term sealing retention compared to platinum-cured silicone |
| Processing Cost | Higher cost due to expensive platinum catalyst; shorter shelf life of raw materials | Cost-effective raw materials with longer shelf life |
After selecting the silicone rubber material, place the pattern in the mold box and evenly distribute the cured silicone rubber. If you are using un-cured silicone rubber, make sure to precisely calculate the weight ratio of the silicone and the catalyst in advance, then mix the silicone rubber with the catalyst and pour it into the box.
Casting of Production Parts
The final step is to pour or cast your production material into the silicone mold, completing the production of the final product. The higher the temperature of the parts you produce, the shorter the lifespan of the silicone rubber mold.
Moreover, the melting or processing temperature of the items you inject into the silicone rubber mold must be lower than the maximum usage temperature of the silicone rubber. Thermoplastic plastics, polyurethane resins, low-melting-point metals, and other silicone rubbers (such as RTV) can all be processed using silicone rubber molds.
However, when injecting, you need to control the pressure reasonably, because excessive pressure will cause the mold to crack, and too low pressure will not be able to fully fill the cavity.
Compared with steel molds, the stability of silicone rubber molds is poorer in this aspect. However, you can use rigid mother mold and fiberglass jacket reinforced silicone rubber molds to improve its stability.
Applications of Silicone Rubber Tooling Technology
Automotive Industry
In the automotive industry, you can use silicone rubber tooling to produce prototypes and small-batch manufactured components, such as gaskets, seals and hoses, etc.
Some personalized interior components for vehicles that require high precision and quality can also be manufactured using this technology. This can save you the time and cost of mold-making.
Aerospace Industry
If you are in the aerospace industry and want to manufacture lightweight yet sturdy components, you can also use silicone rubber to create molds and cavities for turbine blades, seals, and other key components. This meets your requirements for complex geometries and fine details.
Medical Industry
The medical industry has extremely high requirements for the biocompatibility and hygiene of products such as medical devices, prostheses and medical instruments.
Silicone tooling, frequently utilized to manufacture prototypes during medical device development, can not only form complex shapes to meet bespoke clinical application demands but also mitigate safety risks associated with your products.
Consumer Electronics
In the consumer electronics industry, it is usually necessary to manufacture components such as keyboards, sealing rings and casings to protect sensitive electronic components. If you choose a silicone rubber tooling, you can achieve intricate and complex designs as well as high-quality surface effects.
Food and Beverage Industry
Baking molds, ice trays, and other kitchen utensils all need to meet the food-grade product standards. Therefore, the food and beverage industry uses more silicone rubber due to its safety and high-temperature resistance.
Moreover, silicone rubber molds are easy to clean and maintain, making it convenient for your factory to keep a clean environment on a daily basis.
Manufacturing
If you are in the manufacturing industry and are looking for rapid prototyping and high-precision components, silicone rubber tooling technology is a suitable choice for you. Whether it’s for creating prototypes, customizing parts, or producing tools, it can effectively and economically achieve the production of small-batch components.
FAQ
What Should You Note When Casting Silicone Rubber Molds With SLA 3D Printed Master Patterns?
The SLA photopolymer resin may cause the platinum-cured silicone rubber to fail in curing, as the partially unreacted components in the resin can poison and deactivate the platinum catalyst.
We recommend choosing a transparent resin to allow UV light to penetrate and completely cure the printed piece. A layer of isolation film can be applied to prevent the resin from directly contacting the platinum silicone rubber.
How to Ensure the Tolerance Range of Silicone Rubber Tooling?
When designing the mold, you need to fully consider the hardness, viscosity and elasticity of the silicone rubber, as well as the force conditions of the parts, and optimize the design. Adjust the size of the model according to different grades of silicone rubber, as the shrinkage rates of different specifications of silicone rubber are also different.
What Is the Service Life of Silicone Rubber Tooling?
There is no specific figure for this. It mainly depends on your specific application. However, working in a high-temperature and high-pressure environment will accelerate aging because silicone rubber degrades more rapidly under heat and pressure. Repeated cycles of heating and cooling will affect the elasticity of the silicone rubber and also accelerate aging.
How to Choose Silicone Rubber Tooling for Industrial Use Only?
For industrial applications that do not involve human contact, food contact, or extremely low leaching, we recommend choosing tin-cure RTV silicone. This is because it has a lower cost and is more suitable for your pursuit of cost-effectiveness.
What Are the Differences Between LSR Tooling Design and Conventional Plastic Tooling?
LSR has a low viscosity and excellent fluidity. Its exhaust design must be extremely precise; otherwise, flash defects will seriously affect product quality. Moreover, LSR requires heating to trigger the curing reaction, rather than cooling to form as in plastics.
Final Thoughts
Legensilico is a silicone manufacturer in China with over 20 years of manufacturing experience. We can provide you with high-quality and precise silicone rubber molds. If you are interested in further cooperation and want to learn more about silicone-related technical knowledge, please feel free to contact us.
