3D Printing
Wall thicknesses, tolerances and design moves for FDM parts that print right the first time.
3D Modeling / DFM
5 rules
Slant 3DWall thickness
Start FDM walls at 2–3 extrusion widths — with a 0.4 mm nozzle, that’s about 0.8–1.2 mm.
Slant 3DTabs & overhangs
Replace a flat overhanging tab with a chamfer that runs from the part body down to the feature, and round every corner so material flows into it.
Slant 3DHoles & bores
Add a small fillet around a hole’s edges, orient horizontal holes as teardrops to stop sagging, and size the hole up a hair because prints shrink.
Slant 3DHandles
Reinforce the opening with a thickened rim, chamfer the overhang so it self-supports, and where a through-hole isn’t needed, use an indented grip instead so it prints with no support at all.
Slant 3DWalls vs. infill
Add perimeters (walls) before you raise infill; a standard grid or triangle infill around 25% is the reliable default, and infill choice mostly changes how the part fails, not how strong it is.
Supports & Overhangs
2 rules
Slant 3DDesigned supports
If a feature can’t be reoriented to self-support, add a thin modeled support (a wall or web) with a deliberate break-away contact instead of letting the slicer generate one.
Slant 3DBuild orientation
Reorient the part so its overhangs self-support before adding any support — often just rotating ~45° and chamfering the leading edge removes the need for support entirely, and gives cleaner edges all round.
Tolerances & Fit
2 rules
Slant 3DPin tolerances
Fillet the base of a pin so it doesn’t snap, funnel the top of the hole, and make the hole about a quarter of a millimetre larger than the pin.
Slant 3DPrint-in-place clearance
Leave a modeled gap between any two parts that must move or assemble — start around one nozzle width and open it until they run free.
