Parts measure wrong / holes too small

Outer dimensions are off by a few tenths, and holes are consistently undersized.

does not fitholes undersizedpins too tight

Causes, most likely first

Ordered by how often each is actually responsible, not by how interesting it is. Work down the list.

Holes print undersized by design — this is geometry, not a fault

A nozzle traces a polygon inside a circle, so the hole comes out small on every printer ever made. Compensate holes in CAD or with hole compensation. Do NOT try to fix it with flow.

Calibration step: Check dimensional accuracy and hole size →

Flow not calibrated

Flow error reads as dimensional error. Calibrate flow before applying any size compensation, or you will compensate for the wrong thing.

Calibration step: Calibrate flow ratio / extrusion multiplier →

Material shrinkage not accounted for

ABS shrinks about 0.8% and nylon about 1.5%. On a 100 mm part that is 0.8 mm and 1.5 mm respectively — far beyond any tuning.

Designing without a known clearance

Print the fit gauge and find your printer's real number, then design to it.

Calibration step: Find your real clearance for fitted parts →

Open First Layer →
The app walks this in order, generates the test model for your nozzle and filament, and records what you measure so nothing has to be repeated. Free, no account, works offline.