A hole with a pointed top instead of a circular top, designed to eliminate the unsupported flat overhang at the crown of horizontal FDM holes.
A circular hole printed horizontally in FDM has a flat or nearly flat top: a 0° overhang (horizontal) that will sag or close. The teardrop shape replaces the circular top arc with a 45° angled point, which is always within the self-supporting angle. The result is a hole that prints cleanly without supports even though it is horizontal. After printing, the teardrop can be drilled round to the exact diameter if needed.
Use teardrop profiles for any hole with diameter ≥4 mm on horizontal faces in FDM. For smaller holes (2–3 mm) a simple circular hole prints adequately due to bridging. Add the teardrop only to the top half of the circle: the bottom half remains circular. CAD tools: most parametric modellers can create this with a circle + tangent triangle. In SLA, SLS, DMLS: teardrop is unnecessary as these processes either support everything (SLS/DMLS) or require manual supports (SLA) that handle the overhang.
The teardrop changes the hole cross-section: fasteners that pass through will need the hole to be drilled. Do not use teardrops for through-holes that must maintain cylindrical form (e.g. press-fit bearings). Designing teardrops on non-horizontal faces is redundant: check face normal before applying.
Related terms: Overhang / Self-Supporting Angle, Minimum Hole Diameter, Maximum Bridge Length
| Theme | geometry |
|---|---|
| Also called | teardrop hole, D-hole, teardrop aperture |
| Source | Wiki/tech/fdm-fff.md, Wiki/concepts/support-generation.md |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert