What silicone moulds are
Silicone moulds are flexible tooling used for vacuum casting: starting from a master model, a silicone-rubber mould is formed that lets you reproduce small batches of parts in polyurethane resin, with aesthetic and mechanical properties close to those of the final material. It is the fastest and most economical way to obtain a few dozen faithful copies without having to build a metal mould.
How vacuum casting works
The process starts from a well-finished master — often SLA-printed precisely for its smooth surface. The master is suspended in a container and embedded in liquid silicone which, once cured (usually in an oven), forms a solid block. The mould is then cut precisely to extract the master, leaving a cavity that reproduces its shape exactly. From here the two-component polyurethane resin is cast under vacuum: the absence of air eliminates bubbles and lets the material fill every detail. After curing in the oven the part is extracted, and the same mould is reused for several casts as long as the silicone keeps sufficient quality.
Why and when to choose them
Silicone moulds are chosen when you need small batches of realistic parts before — or instead of — investing in injection moulding. The advantages are the reduced time and cost compared with a steel mould, the aesthetic fidelity inherited from the master, and the availability of resins that simulate ABS, polypropylene, rubbers and elastomers, including transparent or mass-coloured ones. Typical cases are functional and aesthetic prototypes in a material close to the final one, pre-series and bridge production, market tests and transparent or overmoulded parts. The limit is the mould’s life, which wears out after a certain number of casts: for high volumes, injection moulding remains necessary.