As 3D printing took off, this became a very common question.
Both processes turn a digital design into a physical plastic part, but they’re fundamentally different in many ways. Some obvious, some less so.
Understanding when to use injection moulding and when 3D printing is the better option depends on your project’s volume, material requirements and its stage in the development cycle.
Let’s compare them in detail.
How Each Process Works
Both processes start from a CAD file and produce a plastic part, but the methods are totally different:
Injection moulding injects molten plastic into a metal mould under high pressure. The plastic fills the cavity, cools and is ejected as a finished part. The cycle takes seconds and repeats identically every time.
3D printing builds the part layer by layer. There’s no mould; the machine deposits or fuses material in thin layers until the part is complete. A typical print takes minutes to hours, depending on size.
Injection Moulding vs 3D Printing Cost Comparison
When it comes to cost, the answer depends on how many parts you need.
| 3D Printing | Injection Moulding | |
| Setup cost | Minimal – no tooling needed | Significant – mould tool required (typically £5,000–£50,000+) |
| Cost per part | Consistent regardless of volume | Falls as volume increases |
| Crossover point | Cheaper below ~100–500 units | Cheaper above that threshold |
| Total cost at 10,000 units | High (each part printed individually) | Low (tooling cost amortised across the run) |
For prototypes and very low volumes, 3D printing wins on cost. Once volumes reach the hundreds, injection moulding becomes more economical and the gap widens rapidly from there.
Speed
3D printing is much faster to get started. A part can move from CAD to prototype within hours, with no tooling needed. That makes it superb for rapid prototyping in the UK and beyond; a design can be tested, adjusted and reprinted the same day.
Injection moulding is faster at scale. Once the mould exists, each part takes seconds. Nothing matches its output.
Materials and Surface Finish
Injection moulding has the clear edge here for production work. It harnesses the full range of engineering thermoplastics: nylon, polypropylene, ABS, polycarbonate, PEEK and hundreds more.
3D printing covers a narrower range of materials, and the resulting materials may be less reliable at scale, though this depends heavily on the methods and materials used.
When to Use Each Process
The key question. Broadly, injection moulding suits when:
- Production runs from hundreds to millions
- Parts needing specific engineering-grade materials
- Tight tolerances and consistent mechanical properties
- Clean surface finish straight off the tool
3D Printing, however, earns its keep earlier in the process and at lower volumes:
- Prototyping and iteration: testing form, fit and function before committing to tooling
- Low volumes where tooling cost can’t be justified
- Jigs, fixtures and production aids
- Reverse-engineering legacy parts with no existing CAD
Using Both Together at BEC
Most projects benefit from using both. We run 3D printing and injection moulding under one roof in New Milton and the natural workflow is to prove the design through printing, then move to moulding once it’s finalised and volumes justify it.
For rapid prototyping, we offer a Fusion F410 printer, which quickly produces functional parts in ABS, PLA, PET, nylon and polypropylene.
When a client has a physical part but no CAD data, we can reverse-engineer it into accurate 3D files ready for tooling development.
If you’ve got a project at any stage, whether concept, prototype or ready for production, get in touch and we’ll advise on which process suits.
