Dimensional accuracy: what to calibrate and what to ignore

Some size errors are worth chasing. Others are physics, and you should design around them instead.

Holes always print tight

Curves are approximated in straight segments, so circles come out about 0.1–0.2mm undersized on every FDM machine ever made. Design holes oversized, use your slicer's hole compensation, or run a drill through afterwards. Do not spend a weekend on it.

Elephant's foot

• Raise Z-offset 0.02mm at a time
• Drop the bed temperature 5°C
• Turn on elephant foot compensation — 0.15 to 0.2mm
• Or chamfer 0.5mm off the bottom edge in the model

Whole-part errors are flow

If a 20mm cube measures 20.3mm, that is over-extrusion, not steps-per-mm. Print a single-wall cube, measure the wall with calipers, and adjust flow. Save the result per brand — Elegoo, Sunlu and Creality Hyper all behave slightly differently.