Vacuum casting: Vacuum casting is a process that makes small batches of plastic parts by pouring polyurethane resin into a silicone mould under vacuum, copying a master pattern.
A master part, often an SLA print, is suspended in a box and liquid silicone is poured around it. Once the silicone cures, it is cut open and the master removed, leaving a cavity. Two-part polyurethane resin, formulated to behave like ABS, polypropylene, rubber and other plastics, is mixed and poured under vacuum to remove bubbles, then cured in an oven.
What it means for the price
A silicone mould is cheap next to a steel tool, but it wears out after a limited number of castings, often a few dozen, so a larger run needs several moulds. Each part also carries labour: mixing, pouring, curing, demoulding and trimming. That puts vacuum casting between 3D printing and injection moulding, at its best from about ten parts to a few hundred.
Example: a mould costing €600 that lasts 20 castings adds €30 to each part in mould cost alone. The figures are an example.
Common confusions
Vacuum casting is not die casting, which forces molten metal into steel dies. Quotometry prices vacuum casting today: the master, the silicone moulds a run needs and each casting. Read vacuum casting vs injection moulding or see the vacuum casting process page.
Go deeper: Vacuum casting vs injection moulding for low volumes