IndiaMost failed or disappointing prints come down to a few design details. Run through this checklist before you upload and your parts will come out right the first time. The numbers are for the FDM printers we use, with a 0.4 mm nozzle and 0.20 mm layers.
Quick reference
| Feature | Design to |
|---|---|
| Minimum wall thickness | 1.2 mm (2 mm+ for load-bearing parts) |
| Smallest pin or post | 2 mm diameter |
| Hole size allowance | +0.2 to 0.3 mm |
| Gap between fitting parts | 0.3 mm (0.2 mm tight, 0.5 mm loose) |
| Overhang without supports | Up to 45° from vertical |
| Bridge without supports | Up to about 10 mm |
| Text depth (raised or engraved) | 0.6 mm or more |
| Text height | 5 mm or more |
Walls and small features
The printer lays down lines about 0.4 mm wide, so walls thinner than about 1 mm may come out patchy or not print at all. Thin pins and posts snap easily, so keep them at 2 mm or more across, or thicker if they will be handled often.
Holes and parts that fit together
Printed holes come out slightly smaller than designed, and printed pegs slightly bigger. If a screw, bearing or second printed part has to fit, design the hole 0.2–0.3 mm larger. For snap-fits and lids, leave a 0.3 mm gap between the two surfaces. For a precise fit, print one test piece first, then adjust.
Overhangs, bridges and supports
Each layer has to rest on the one below. Surfaces that lean out more than 45° from vertical need temporary supports, which add print time and leave a rougher surface where they are removed. You can often avoid them:
- Add a 45° chamfer under ledges instead of a flat shelf.
- Make horizontal holes teardrop-shaped at the top.
- Design flat-bottomed parts so they can lie on the bed.
- Split complex parts into two pieces that print flat and glue together.
Text and logos
Raised or engraved lettering needs to be at least 0.6 mm deep to show up, and about 5 mm tall to stay readable. Bold, simple fonts print much better than thin or decorative ones.
Strength and print direction
Prints are strongest along each layer and weakest between layers. A hook printed standing upright can snap along a layer line; the same hook printed lying on its side is several times stronger. If a part carries load, email us how it will be used, or design it to lie flat. For heat and outdoor use, read PLA vs PETG.
Check the file itself
- Units: exported in millimetres. See how to export an STL.
- Watertight: the model must be a closed solid with no holes in its surface. Free apps such as PrusaSlicer or Meshmixer can find and repair holes.
- No zero-thickness faces: single flat surfaces, common in SketchUp and Blender models, have no volume and can't print.
- One solid per part: overlapping shapes are usually fine, but merge them if the quote tool reports errors.
Questions
What is the minimum wall thickness for 3D printing?
Design walls at least 1.2 mm thick for FDM printing with a 0.4 mm nozzle, and 2 mm or more for parts that carry load.
How much clearance do 3D printed parts need to fit together?
Leave about 0.3 mm between parts that must fit together. Use 0.2 mm for a tight fit and 0.5 mm for a loose one, and add 0.2–0.3 mm to holes.
Do I need supports for my 3D print?
Surfaces that lean out more than 45° from vertical, and bridges longer than about 10 mm, need supports. Chamfers and laying parts flat often avoid them.
How big should text be on a 3D print?
Make raised or engraved text at least 0.6 mm deep and about 5 mm tall, using a bold, simple font.