Silicone moulds are a micro-production technique referred to as "soft tooling" given that the mould is made of a soft material. It mainly consists of the realisation of a silicone die of the "master" object. When the silicone hardens around the master, the latter can be removed leaving an imprint which is basically a mould that can be filled with cast resin.
The most common cast resins are dual-component polyurethane based and are formulated to have similar technical specifications to the most common production materials, such as plastics or silicone based rubber
- PA-like materials
- PA-GF-like materials
- ABS-like materials
- Special materials resistant to UV radiation
- Special materials resistant to high temperatures (>180°C)
- Silicone-based rubber
- Others available on request (according to availability at Basf/DuPont)
Thanks to the suppleness of the matrix of a silicone mould, it is ideal for realising complex objects, full of details and small undercuts that are "resolved" by exploiting the suppleness of the silicone matrix, i.e. forcing the expulsion of the component that is, in some way, extracted from the silicone mould. Due to the level of mechanical stress and chemical aggression, a silicone mould has a working life of no more than 20-30 extractions (according to the complexity of the object and the aggressiveness of the resin. Resins for silicone based replicas can be pre-pigmented to create objects which are already coloured as desired.
Given that often the master used to create the mould is finished off to reduce the ability of the mould to retain the objects, the parts produced using this system have a good or excellent aesthetic finish, and are practically undistinguishable from series manufactured products. The negative aspect of this solution is very often the longer preparation time compared to direct printing prototypes (they need about 3 working weeks) and the "soft tooling" costs (with the burden of ensuring the master undergoes fine finishing operations); moreover, it is a procedure where most of the work does not involve an automated machine, but a number of different phases (and often rather slow due to the catalysis of the resins that takes from a few hours to 2 days per piece) almost all done by hand. The silicone mould technique is also ideal for reproduction of perfectly transparent objects, as seen in the photo.