Technology
FDM 3D printing
Fused deposition modelling — molten thermoplastic laid down layer by layer.
Dimensional tolerance
±0.3 mm or ±0.3 % — whichever is greater
We hold this tolerance on every part, whichever slicer settings we use. Layer height, infill and nozzle are production decisions we make for you.
Materials for this process
- PLA
Easy to print, biodegradable, great for prototypes and decorative parts.
- PETG
Tougher and more heat-resistant than PLA, good for functional parts.
Design rules
Design to these and the part prints first time.
Wall thickness
On a 0.4 mm nozzle the practical minimum is 0.8 mm (two perimeters). Anything thinner prints as a single wobbly bead and delaminates under load. For load-bearing walls target 1.2–1.6 mm. Text and embossed detail need at least 0.8 mm stroke width and 0.6 mm depth to stay legible.
Holes, bores and shafts
Printed holes come out 0.10–0.20 mm undersized from extrusion overlap. Oversize modelled holes by 0.2 mm on diameter, or drill to size after printing. For fastener holes meant for repeated assembly, design for a heat-set brass insert instead of printed threads.
Bridging limits
Unsupported horizontal spans work up to about 10 mm in PLA and PETG with active cooling; beyond that the bridge sags. For longer spans use a shallow arch or a chamfer so the printer can ramp up gradually.
Overhangs
Overhangs print cleanly up to 45° from vertical. Between 45° and 60° the surface degrades but usually holds; past 60° the part needs support or a redesign. Replacing steep overhangs with 45° chamfers removes the support-removal step entirely.
Orientation for strength
Parts are strongest along the layer plane and weakest across layer lines. A cantilever printed lying flat is roughly 2–3× stronger than the same part printed standing up. Tell us the load direction and we orient layers perpendicular to it.
Chamfers and fillets
A 0.5 mm × 45° chamfer on any mating edge hides the first-layer bulge and helps parts self-align during assembly. Internal fillets of 1–2 mm radius at stress concentrations more than double fatigue life on load-bearing parts.
Geometry to avoid
- Sharp knife-edges — they print as a rounded 0.4 mm tip anyway.
- Threads finer than M6 — use heat-set inserts.
- Long thin cantilevers standing vertically — they wobble and delaminate.
- Enclosed cavities with no drain hole — trapped support material can't be removed.
Clearance calculator
Fits between mating parts.
Tolerance calculator
Pick clearance for millimetre-sized parts
Per-side clearance
0.25 mm
Diametral clearance
0.50 mm
hole − shaft
Model the hole at
10.50 mm
for a 10.0 mm shaft
Base recommendation 0.25 mm. Tune in 0.05 mm steps from a small test print.
ABS and TPU are not in our current stock — we quote them as a special run by email. Email us for a quote.
Assumes a 0.4 mm nozzle at 0.2 mm layer height on a well-calibrated printer. For diameters under 3 mm, add another 0.05–0.10 mm per side to account for extrusion overlap on the inside of the hole.
| Material | General | Press fit | Sliding fit | Threads | Hinges |
|---|---|---|---|---|---|
| PLA | ±0.15 mm | 0.10–0.15 mm | 0.20–0.30 mm | 0.20 mm | 0.30 mm |
| PETG | ±0.20 mm | 0.15–0.20 mm | 0.25–0.35 mm | 0.25 mm | 0.35 mm |
Values are per-side clearance between mating surfaces. Double them when specifying diameter-on-diameter (hole vs. shaft).
These numbers assume a 0.4 mm nozzle at 0.2 mm layers on a calibrated machine. If a first assembly is too tight, adjust in 0.05 mm steps — the smallest change FDM reliably resolves. Print a small tolerance test alongside the real part rather than reprinting the whole assembly.
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