3D printing builds a part layer by layer straight from a 3D model, with no tooling. It is used for prototypes, fixtures, small batches and shapes that cannot be machined. Plastic processes such as FDM, SLA and SLS are common and affordable; metal printing makes strong steel, titanium and aluminium parts at a much higher cost.
Quick facts
- Main processes
- FDM (filament), SLA/DLP (resin), SLS/MJF (nylon powder), metal (DMLS/SLM)
- Typical accuracy
- About ±0.1–0.3 mm (±0.0039–0.0118 inch) for plastics
- Layer height
- About 0.05–0.3 mm (0.0020–0.0118 inch), by process
- Materials
- PLA, ABS, PETG, nylon, resins; steel, titanium, aluminium
- Best for
- Prototypes, jigs, small batches, complex shapes
- Usually priced
- By material volume, machine time and finishing
Which process for which part
| Process | Strengths | Typical parts |
|---|---|---|
| FDM | Cheap, strong enough, big parts | Jigs, fixtures, housings, prototypes |
| SLA / DLP | Fine detail, smooth surface | Show models, small detailed parts, casting patterns |
| SLS / MJF | Strong nylon, no supports | Functional prototypes, small batches |
| Metal (DMLS / SLM) | Full-strength metal, internal channels | Conformal-cooled mould inserts, aerospace and medical parts |
When 3D printing makes sense
- One-off prototypes to check fit before making a mould or tool
- Inspection and assembly fixtures in the workshop
- Small batches where a mould would cost too much
- Shapes with internal channels or lattices that cannot be machined
- Investment casting patterns for one-off castings
What to send the printing shop
- 3D model as STEP (or STL for plastics)
- Process and material, or what the part must do (strength, heat, flexibility)
- Critical sizes and fits, and tolerance needed
- Surface finish wanted (as printed, sanded, painted)
- Quantity and colour
- Whether threads and holes should be printed or machined later
Need 3d printing (additive manufacturing) done?
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Questions
- Is 3D printing cheaper than machining?
- For one-off plastic prototypes and complex shapes, often yes. For simple metal parts or any part in larger numbers, machining or moulding is usually cheaper and stronger.
- How strong are 3D printed parts?
- SLS nylon and metal-printed parts are strong enough for working parts. FDM parts are weaker between layers, so the print direction matters for loaded parts.
- Which file should I send for 3D printing?
- STEP is best because it keeps exact geometry. STL works for plastic printing; make sure it is exported fine enough that curves are smooth.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 18 October 2026.