3D printing: design rules
Building parts layer by layer (FDM, SLA/resin, SLS powder, metal powder bed) for prototypes and complex shapes.
Typical tolerance
Typical: FDM ±0.2–0.5 mm, SLA and SLS about ±0.1–0.3 mm. Printed holes come out slightly small.
Files to send
STL or 3MF for printing; STEP if the shop should check geometry first.
Common materials
PLA, PETG, ABS, nylon, resin, SLS nylon, aluminium and stainless steel (metal printing). PLA softens at about 60 °C.
The rules, with reasons
- Wall thickness. At least 1.2 mm for FDM and about 0.8–1 mm for SLA and SLS; walls should be at least two nozzle widths. Why: Thinner walls fail to print or break.
- Overhangs. Keep overhangs to about 45° or less in FDM, or plan supports. Why: Steeper overhangs droop without support and leave rough surfaces.
- Holes and fits. Add about 0.2–0.4 mm clearance to holes and mating parts. Why: Printed holes shrink and layers add roughness.
- Orientation. Print so the main load is along the layers, not across them. Why: Parts are weakest between layers.
- Heat. Do not use PLA for parts that see heat above about 60 °C; use PETG, ABS, nylon or a metal part. Why: PLA deforms in a hot car or near a heater.
Before you ask for a quote
- Technology and material
- Quantity
- STL or 3MF in millimetres
- Surface finish needs
- Temperature and load of the use
Common mistakes
- Wrong units in the file
- Zero clearance on mating parts
- PLA in a hot environment
- Walls thinner than two nozzle widths
Agents and scripts can check a design automatically with the check_design MCP tool or POST /api/design-rules. How to connect.
Request a quote Find manufacturers
Typical rules of thumb, not a guarantee. The manufacturer's own design guidelines override them: ask for them and check your design against both before ordering.