A small 45° chamfer (0.3–0.5 mm) at the base of vertical features compensates for the first-layer squish that causes sharp-edged FDM parts to have wider bases than designed.
The first layer of an FDM print is intentionally squished into the bed at 80–120% flow rate for adhesion. This over-extrusion causes the plastic to spread outward, creating the 'elephant foot': a flare at the base that can be 0.2–0.5 mm wider per side than the designed dimension. The effect is worse with higher bed temperatures and lower first-layer heights. A 45° chamfer (counter-bevel) at the base absorbs this spread and produces a flat, dimensionally accurate base.
Add a 0.3–0.5 mm chamfer to all vertical wall bases. Some slicers offer an 'elephant foot compensation' setting that offsets the first N layers inward: use this as the primary fix and add a chamfer in the CAD as a backup for critical parts. For SLA, the first layers over-cure to the build plate in a similar way; a 0.2 mm chamfer or the slicer's 'anti-aliasing' setting helps. SLS and DMLS do not suffer elephant foot: no first-layer adhesion squish.
A chamfer that is too large (>1 mm) removes functional material and looks unintentional. Do not rely on elephant foot compensation in the slicer alone for precision parts: always verify with callipers on a first article. The effect is stronger with ABS and PETG than with PLA due to higher printing temperatures and more bed adhesion required.
Related terms: Fillets vs Sharp Internal Corners, Minimum Wall Thickness
| Theme | geometry |
|---|---|
| Also called | elephant foot, base chamfer, first layer brim, bottom chamfer |
| Source | Wiki/tech/fdm-fff.md, Wiki/concepts/calibration.md |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert