When vacuum casting beats injection moulding for your first parts, when it does not, and how to bridge the gap with small batches.
Short answer: vacuum casting is usually the right route for the first 10 to 100 parts of a design. Injection moulding wins once the design is settled and you need hundreds or thousands of identical parts.
By David Kent. Complete Fabrication has been vacuum casting since the 1980s.
Vacuum casting uses a silicone mould taken from a master pattern, instead of a metal tool. The mould is quicker and cheaper to make, so you can test the design in a production-like material before committing to tooling. At our workshop, most projects complete in two to three weeks from pattern approval, with tolerances of ±0.5 mm on most dimensions.
Parts can be cast in polyurethane, silicone and epoxy resins that simulate production plastics, including clear, self-coloured and biocompatible grades. Self-coloured parts need no painting, and two shore hardnesses can be combined in one moulding.
The two are not rivals. Vacuum casting can supply early batches while the injection tool is made, so product launches and field trials do not wait. Our low-volume production work often runs this way, with batches in the low hundreds and full assembly, printing and packaging included.
Send your CAD and quantity to Info@compfab.co.uk and we will say which route fits and quote it.
It suits batches of 10 to 50 parts for trials, and runs in the low hundreds for low-volume production. A silicone mould generally gives around 20 castings, and more depending on the complexity of the part.
For small quantities, yes, because silicone moulds are faster and cheaper than metal tools. For large quantities of a final design, injection moulding costs less per part.
They can mimic them closely. We use thermoset-simulant polyurethane resins that replicate the behaviour of production materials.
Send your CAD files or drawings and tell us when you need the parts. Call +44 1223 836837 or email info@compfab.co.uk.
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