Circles and holes not round (oval holes)
Round holes and cylinders come out slightly oval or flat-sided, usually squashed in the same direction every time.
Also described as oval holes, egg shaped holes, circles not round, out of round, elliptical, flat sided circles, squashed circles
Try these in order
Most likely and quickest to check first. Change one thing at a time so you know what fixed it.
Loose belt on one axis
If circles are always squashed the same way, one axis loses a little movement each time it changes direction.
- Tension both belts so they feel and sound about the same when plucked.
- Tighten the grub screws on the motor pulleys, with one sitting on the flat of the shaft.
Play in the bed or print head
- With the printer off, try to rock the bed and the print head by hand. Tighten the eccentric nuts on V-wheels until there's no wobble but the wheels still turn.
- Check the frame and gantry screws are tight.
Model saved at low resolution
Curves exported with too few facets print as polygons instead of circles.
- Re-export the STL with a finer resolution from your CAD program.
- Look for flat sides on curves in the STL viewer before slicing.
Very small holes
Holes of a few millimetres or less come out smaller and less round than larger ones.
- Model small holes slightly oversize, or print them undersize and drill them out to the exact size.