Parts the wrong size, holes too small
Prints come out slightly bigger or smaller than designed, and holes and pegs don't fit together.
Also described as holes too small, parts don't fit, dimensional accuracy, wrong dimensions, too tight, too loose, shrinkage, won't fit together
Try these in order
Most likely and quickest to check first. Change one thing at a time so you know what fixed it.
No clearance in the design
Two parts drawn exactly the same size won't fit. Printed holes always come out slightly small.
- Add clearance for the kind of fit you want, usually 0.1 to 0.4 mm per side for FDM.
- Use the tolerance guide to size holes and pegs.
Over-extrusion
- Calibrate the flow rate, then measure a test cube again.
Elephant's foot
- If only the bottom is too big, see elephant's foot.
Model in the wrong units or scale
A part 25.4 times too small or large was saved in inches and opened as millimetres, or the other way round.
- Check the size in the STL viewer and rescale with the unit converter.
Shrinkage
- ABS, ASA and nylon shrink as they cool. Scale them up by about 0.5 to 1% if it matters.