Soft Tooling Selection and Amortization for Micro Runs
Soft tooling selection balances rapid lead times against progressive cavity wear, requiring direct NRE payment and scrap inflation modeling for micro runs.
RTV Casting
Meaning
Room temperature vulcanization technique for creating flexible molds enables the rapid reproduction of complex geometries without the need for expensive metal tooling. Engineers use rtv casting to make high fidelity silicone molds from a master pattern produced by 3D printing or CNC machining. The process is characterized by the use of liquid silicone that cures into a durable elastomer at ambient temperatures.
It ceases to be the optimal choice when the geometry requires rigid mold halves for high pressure injection.
Curing Protocol
Polymerization of the silicone rubber occurs over a period of twelve to twenty four hours depending on the catalyst used. In rtv casting, the liquid mixture is degassed in a vacuum chamber to ensure that no air is trapped against the surface of the master pattern. The resulting mold is flexible enough to allow for the removal of parts with deep undercuts.
Stable temperature and humidity are necessary to ensure a consistent cure.
Detail Resolution
Capturing fine surface textures is a hallmark of this molding method. Because the silicone is applied in a liquid state, rtv casting reproduces every detail of the original pattern down to the micron level. This makes the process popular for creating aesthetic models and medical device housings.
The flexible nature of the mold allows for complex internal features that would be impossible to release from a steel tool.
Production Scale
Capability of a single silicone tool is typically limited to twenty five or fifty shots before the mold begins to degrade. As the resin is cast into the tool, the heat and chemical reactions slowly break down the silicone surface. Rtv casting is therefore reserved for the very early stages of product development or for highly customized luxury goods.
Manufacturers in the specialized zones of Dongguan use this process to provide rapid turnaround for global design firms.