Fundamentals
What is additive manufacturing, and how does it work?
Additive manufacturing, usually called 3D printing, builds a part layer by layer directly from a CAD file, with no tooling. Because there is no mould or fixture to pay for, it suits one-offs, prototypes, complex shapes and runs up to a few hundred parts. For polymer parts, the main processes are FDM, SLA, SLS and PolyJet.
Reviewed by HenleyPrint3D engineers3 min readUpdated
Key takeaways
- No tooling: cost per part stays almost flat from 1 to 100 parts.
- Complexity adds little cost. Internal channels, lattices and merged assemblies cost little extra.
- Four processes cover most polymer work: FDM, SLA, SLS and PolyJet.
- At several thousand identical parts, moulding or machining usually wins on unit cost.
Suits
Engineers new to 3D printing, or checking when it beats machining and moulding.
Worth knowing
For thousands of identical plastic parts, or tolerances tighter than about ±0.1 mm, moulding or machining is usually the better route.
How it works
- Design the part in CAD and export STEP or STL.
- Software slices the model into layers.
- The machine builds the layers: melting filament, curing resin, fusing powder or jetting photopolymer.
- The part is cleaned, supports removed and finishing applied.
The four 3D printing processes we run
| Process | Builds with | Max build | Tolerance | Lead time from |
|---|---|---|---|---|
| FDM | Melted filament | 1000 × 1000 × 1000 mm | ±0.5% (min ±0.3 mm) | 1 calendar day |
| SLA | UV-cured resin | 350 × 250 × 250 mm | ±0.5% (min ±0.1 mm) | 1 calendar day |
| SLS | Laser-fused PA12 powder | 165 × 165 × 300 mm | ±0.3% (min ±0.3 mm) | 2 calendar days |
| PolyJet | Jetted photopolymer | Quoted per part | Quoted per part | Quoted per part |
When to use additive manufacturing
| Situation | Choose |
|---|---|
| 1 to a few hundred parts | 3D printing |
| Complex internal geometry, consolidated assemblies | 3D printing |
| Tight tolerance (tighter than about ±0.1 mm) or metals | CNC machining |
| Thousands of identical plastic parts | Injection moulding |
Because there is no tooling, cost per part tracks material and machine time. A part with an internal channel costs about the same as a solid block of the same size, which is why consolidated assemblies and lattices are practical.
To pick between the four processes, see how to choose a 3D printing process. Before you send a file, check the design rules for 3D printing. Where printing meets moulding on cost, see 3D printing vs injection moulding.
Frequently asked questions
Is additive manufacturing the same as 3D printing?
In practice, yes. Additive manufacturing is the formal industrial term and 3D printing is the common name. Both describe building parts layer by layer from a digital model.
How accurate is additive manufacturing?
Typical polymer processes hold roughly ±0.1 to ±0.5 mm depending on process, part size and material. Features that need tighter control are usually machined or reamed after printing.
Is 3D printing strong enough for end-use parts?
Yes, in the right material and orientation. Nylon PA12 from SLS and engineering thermoplastics from FDM are widely used for functional parts, though layered parts are weaker across layers than along them.
How long does 3D printing take?
Build time depends on part height and volume, from under an hour to several days. Lead time including finishing and inspection can start from one calendar day for simple FDM or SLA parts.
When is machining or injection moulding better than 3D printing?
Machining suits tight tolerances and certified metals; injection moulding suits thousands of identical parts. Additive manufacturing is usually the better choice for complex parts and low volumes.
Get started
Talk to an engineer about your part.
Send us your CAD or describe the problem. We recommend the process, material and finish, and quote with the lead time up front.
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