The manufacturing of silicone rubber molds based on Rapid Prototyping (RP) technology has become an essential process in producing high-quality, detailed parts. Due to the non-reactive nature of the RP prototype material with silicone rubber, the production process is efficient, and it avoids deformation or wrinkling. This leads to a surface finish that is as precise as that of high-quality plastic parts. In this article, we will explore the step-by-step process of creating silicone rubber molds, specifically focusing on an example of a cover for an electrical appliance using the LOM prototype method.

Step 1: Surface Treatment of the Prototype

RP technology typically leaves step-like or seam-like patterns between the layered sections of the prototype. To ensure a smooth surface, it is necessary to carry out surface treatments such as sanding, moisture-proofing, and reinforcement. These treatments enhance the surface smoothness of the prototype and improve its resistance to moisture, adhesion, and other factors. The smoother the surface of the prototype, the better the silicone rubber mold will replicate the surface quality, ensuring that the molded parts also maintain a high surface finish and are easier to demold.

Step 2: Creating the Mold Frame and Fixing the Prototype

Based on the geometry of the prototype and the specific requirements for the silicone rubber mold, the mold frame’s shape and size are designed. The mold frame dimensions must be appropriate to ensure a secure fit for the prototype. Before fixing the prototype in the frame, it is essential to determine the parting line and gate location. These elements are crucial as they affect the smoothness of the injection process, ease of demolding, and the overall quality of the molded product. Once the parting line and gate are finalized, the prototype is securely fixed within the mold frame.

Step 3: Measuring, Mixing, and Vacuum Degassing of Silicone Rubber

The amount of silicone rubber used should be precisely measured based on the mold frame’s size and the density of the silicone rubber. After measuring the appropriate amount of silicone rubber, the correct ratio of hardener is added and thoroughly mixed. The mixture is then subjected to vacuum degassing, where air bubbles trapped in the mixture are removed. The degassing process ensures that the silicone rubber mixture is void of air, which can otherwise affect the mold’s quality. The degassing time should be carefully monitored based on the achieved vacuum level.

Step 4: Silicone Rubber Pouring and Curing

After vacuum degassing, the silicone rubber mixture is poured into the mold frame that holds the prototype. During the pouring process, care must be taken to avoid air entrapment, ensuring the mold cavity is fully filled. After pouring, the mold undergoes a second vacuum degassing process. This step removes any air that was trapped in the silicone mixture during the pouring or from within the prototype’s cavities. The vacuum degassing time should be longer than the previous stage to ensure thorough removal of gas. After degassing, the silicone rubber mold will cure either at room temperature or through heat curing, which speeds up the curing process.

Step 5: Removing the Mold Frame, Cutting the Mold, and Extracting the Prototype

Once the silicone rubber has fully cured, the mold frame is removed, and any excess components, such as gate runners, are trimmed away. Next, the mold is cut open along the parting line, which was marked earlier on the prototype. The prototype is carefully removed from the silicone mold, and the mold cavity is cleaned as needed. The finished silicone rubber mold is now ready for use in the vacuum casting of resin or plastic parts, allowing for the production of high-quality products in small to medium quantities.

Advantages of Using Silicone Rubber Molds Based on RP Technology

1. High-Precision Surface Finish
   Since RP prototypes are directly replicated in silicone rubber molds, the molds capture the fine details and high precision of the original prototype. This results in molded parts with a surface finish comparable to high-quality plastic products.
2. Rapid Prototyping and Shorter Production Cycles
   Silicone rubber molds created through RP technology significantly shorten the prototyping and production timelines. The process is faster than traditional methods, allowing companies to rapidly iterate on designs and speed up time-to-market.
3. Cost-Effective for Small Production Runs
   Silicone rubber molds are cost-effective, especially for small to medium production runs. Since the mold-making process does not require expensive machinery, it is an affordable option for producing prototypes or small batches of parts without the high costs associated with metal molds.
4. Flexibility and Ease of Use
   Silicone rubber is highly flexible, making it easier to create molds for parts with complex geometries, intricate details, or undercuts. Additionally, the molds can be easily modified if needed, further enhancing the mold-making process’s flexibility.
5. Material Efficiency and Waste Reduction
   The RP process allows for precise modeling of prototypes, which means the resulting silicone rubber molds are made with minimal waste. The exact replication of the prototype reduces the need for excess material or corrections after the mold is made.

Conclusion

The silicone rubber mold manufacturing process, when based on Rapid Prototyping (RP), provides a fast, cost-effective, and precise method for producing high-quality molds. The detailed, step-by-step process ensures that the final molded products exhibit superior surface finishes and dimensional accuracy, making this technique ideal for prototyping, small production runs, and industries requiring high-precision components. As industries continue to push for faster product development and shorter lead times, silicone rubber molds based on RP technology are becoming an increasingly popular choice for manufacturers seeking high-quality results with lower costs.