Silicone rubber molds are widely used in small batch production and prototyping, but their high material cost often constitutes a large portion of the total expense, particularly for large-sized single pieces. To address this, there has been a continuous effort to develop cost-saving techniques that reduce the material consumption of silicone rubber while still achieving high-quality molds. One such method involves the substitution of a portion of the silicone rubber material with more affordable alternatives, like plaster, to significantly lower costs. This article will explore a cost-effective process for manufacturing silicone rubber molds, particularly when dealing with parts that have large cavities or complex geometries.

1. Suitable Prototype Features for Economical Silicone Rubber Molds

Not every part design is ideal for the economical method of silicone rubber mold making. When considering both economic feasibility and efficiency, certain types of parts are more suitable for this method. These include:

(1) Parts with Large Internal Cavities

Some parts have large cavities where filling the entire void with silicone rubber would lead to considerable waste. In these cases, a more efficient method is used where a layer of clay or plasticine is applied to the cavity’s interior. Then, plaster is poured into the cavity, and after it hardens, the clay is removed. The remaining gap is then filled with silicone rubber, saving significant material.

(2) Parts with Varying Section Sizes Along One Direction

Parts that have a significant difference in cross-sectional dimensions along a single direction are also suitable for this cost-effective process. These parts can be divided into two types:

1. Parts with Step Features or Similar Structures: For parts with stepped features, filling the entire mold with silicone rubber below the step would lead to unnecessary waste. The economical method involves replacing the silicone rubber in areas around the step with plaster, significantly reducing material usage.
2. Parts with Corner Features: For parts with internal corners, excessive silicone rubber in these areas can be replaced with plaster, further saving on material costs.

2. Process Flow for Economical Silicone Rubber Mold Manufacturing

The process for creating an economical silicone rubber mold, which involves using plaster as a substitute for part of the silicone rubber material, follows these key steps:

(1) Preparing the Prototype

The prototype is first cleaned and prepared. It is then placed on a flat surface, fixed securely, and surrounded by a mold frame. The gap between the prototype and the mold frame should be consistent. A release agent is applied to the inner surface of the mold frame to ensure easy removal of the mold later. After this, a layer of clay or plasticine is applied to the prototype surface.

(2) Pouring the Plaster Backing

A mixture of plaster is prepared and poured into the mold frame to cover the prototype. The plaster is allowed to solidify, providing a stable backing for the silicone rubber mold.

(3) Removing the Clay

Once the plaster has hardened, the clay or plasticine is carefully removed. The cavity left by the clay needs to be thoroughly cleaned to prevent it from affecting the surface quality of the mold.

(4) Mixing and Pouring the Silicone Rubber

The volume of silicone rubber needed is calculated based on the amount of clay that was removed. After considering potential material loss, the silicone rubber is prepared and mixed uniformly. The mixture is then placed in a vacuum chamber to remove any trapped air bubbles. Once degassed, the silicone rubber is poured into the mold.

(5) Removing the Prototype

After the silicone rubber has been poured and allowed to cure (either at room temperature or with heat), the prototype is carefully removed from the mold. This leaves behind the finished silicone rubber mold, which is ready for use in casting parts or prototypes.

Conclusion

This cost-effective method for creating silicone rubber molds by incorporating plaster as a substitute material provides a significant reduction in material costs, making it ideal for large or complex parts that would otherwise lead to excessive waste. By using clay or plasticine to create cavities and replacing certain sections of the mold with plaster, manufacturers can achieve high-quality silicone rubber molds without the high cost typically associated with this material. This process is not only economically viable but also efficient for small batch productions and prototyping, allowing for more affordable production of detailed and intricate parts.