Front page / Should I use 3D printing, urethane casting or injection moulding for my quantity?
Should I use 3D printing, urethane casting or injection moulding for my quantity?
As a rule of thumb from published comparisons, 3D printing suits roughly the first tens of parts, urethane casting in silicone moulds suits about 20 to a few hundred, and injection moulding becomes the cheaper route from around a few hundred parts upward. In one worked comparison by Fictiv, injection moulding became cost-effective at about 500 parts, and urethane casting was most often used for 20 to 100 parts.
The crossover depends on part size, complexity, finish and the material you need, so the numbers below are planning guides. The bigger question is often not cost but whether the parts behave like the final product.
How the three compare
| 3D printing | Urethane casting | Injection moulding | |
|---|---|---|---|
| Tooling | None | Silicone mould made from a master pattern | Machined aluminium or steel mould |
| Parts per tool | Not applicable | Fictiv: up to about 20 per mould in its cost article; its RTV guide says typically 15 to 30, with up to 100 possible depending on the casting material | Fictiv: up to about one million from one mould |
| Typical quantity | Fictiv: most printed runs stay under about 100 parts | Fictiv: realistically up to about 300, most often 20 to 100 | Fictiv's example: cost-effective from about 500 |
| Materials | Printing resins, nylons and filaments | Polyurethanes that imitate ABS, PC, PP or rubber, in a range of Shore hardness | The actual production thermoplastic |
| Tolerance guide | Process dependent | Xometry: about ±0.010 in or ±0.003 in per inch, whichever is larger | Tighter, depending on resin and size |
Why urethane casting sits in the middle
A urethane casting mould is made by pouring silicone around a master pattern, often 3D printed. Fictiv's RTV guide notes the silicone can take up to 24 hours to cure and then reproduces fine features, down to about 0.6 mm (0.025 in). Because each mould wears out after a few dozen castings, the cost per part stays fairly flat: more parts simply mean more moulds and patterns. That is why it is efficient for tens to low hundreds of parts but loses to injection moulding as quantities climb.
Cost is not the only test
- Material match. Fictiv points out that a nylon print may behave very differently from the plastic you will finally use, which matters for testing. Cast urethanes are closer but still not the production resin.
- Process match. Only injection moulding shows real shrinkage, weld lines, sink and warp. Problems found here cost less to fix before the production mould.
- Certification. Tests that must be done on production-representative parts usually need moulded parts.
- Speed. Printing gives parts in days, casting within a short time once the pattern exists, moulding only after the mould is built.
A common route
- 3D print early prototypes to check form and fit.
- Cast urethane parts for a pilot batch, user trials or marketing samples.
- Move to a prototype or bridge mould when the design is close to frozen and real material is needed.
- Build the production mould once the design and demand are settled.
Crossover points here come from one supplier's worked example and published service pages. Get quotes for your own part at two or three quantities before choosing.
Questions buyers ask
Can I skip urethane casting?
Often, yes. If the design is settled and you need hundreds of parts in the real material, a low-cost prototype mould may be a better use of money.
Are cast parts strong enough for testing?
For many fit and user tests they are. For tests where impact, heat or chemical resistance matter, check the cast material's data against the production resin.
Why is the first injection moulded part so expensive?
Because the mould has to be built first. The mould cost is spread across the parts, so the price per part falls quickly as quantity rises.
Can 3D printing be used for production?
For small runs of complex or customised parts it can. For simple parts in large numbers, moulding is usually much cheaper per part.