Dimensional Accuracy
Improve parts that print successfully but are slightly too large, too small or do not fit together.
FDM printing cannot reproduce every dimension perfectly, but well-calibrated printers can produce highly accurate functional parts.
Start by printing a known calibration object and measuring it with digital calipers.
Do not immediately change X or Y motor calibration. Modern printers are usually mechanically calibrated correctly from the factory.
Check extrusion first. Over-extrusion can make outside dimensions larger and holes smaller.
Elephant foot can also interfere with assemblies, especially around the bottom of parts.
Many slicers provide XY compensation or hole compensation settings.
Remember that holes often print slightly smaller than their designed diameter because of extrusion geometry.
Print orientation can also influence accuracy.
Allow parts to cool before measuring them.
For mating parts, include realistic clearance in the CAD model. Two parts designed with exactly the same nominal dimension may not slide together after printing.
As a starting point, many FDM assemblies require a small intentional clearance, but the ideal value depends on printer, nozzle, material and desired fit.
Common causes: over-extrusion, elephant foot, inappropriate CAD tolerances, slicer compensation, material shrinkage.