The technology of vacuum casting into silicon molds was invented in the sixties in the GDR. Vacuum cast duplication consists in producing a master model on 3D printers or CNC machines. The model is hand finished and embedded in silicone rubber. After solidification, the silicone master model is cut. Once the silicone mold is completed, it can be inserted into a vacuum casting machine and inject polyurethane mixture in to mold under vacuum. When the mixture cures, the part is removed and the mold can be reused.
The main advantage of this technology is the multiple reusability of the silicone mold and the production of a set of almost identical copies from a material very similar to the final for serial production. This makes vacuum casting into silicone molds ideal for the production of pre-series parts and small series.
The advantage of polyurethane casting compounds is their great variety from foam materials to rubber to transparent and very strong materials. Different types of casting compositions can be cast into the same mold, so that the final product can be fine-tuned to the smallest detail.
Final parts could be painted, sand-blasted or plated.
At the Protocast, we use a machine of our own design with an output capacity of 40 kg per hour for mixing and venting silicone. We are able to produce very large silicone molds.
In our prototype workshop we use vacuum casting machines of our own design, which have a great advantage over industrially manufactured machines, especially in maximum mold dimensions. Our largest vacuum chamber has a volume of 400 liters and the mold dimensions can be up to 550x1000 mm making it one of the largest in the Czech Republic.
The vacuum casting technology is further improved by the possibility of solidifying the mixture in heated autoclaves under high pressure, thereby minimizing the amount and size of bubbles in the casting.
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