Fits in 3D Printing: Loose, Sliding or Tight?
How much clearance a 3D-printed part needs depends on what it's supposed to do. A cover meant to come off easily needs a different fit than an end cap meant to sit firmly. Instead of using one universal value, the fit should be chosen by function and verified with a short test print for important parts.
Three practical fit types
Loose fit: the part should go in easily, come off without force, and forgive minor print deviations. Typical: lids, guides, parts that are removed often. Sliding/plug fit: the part should go in in a controlled way, with little wobble, while still being removable. Typical: adapters, guide parts, end caps. Tight fit: the part should clamp noticeably and hold without extra fastening if possible. Risk: too little clearance can make the part impossible to assemble, or cause it to crack when pressed in.
Defining clearance unambiguously
Example: a tube with a 30.00 mm outer diameter, desired opening 30.40 mm. Total difference: 0.40 mm. Radially, i.e. per side: 0.20 mm. Vuolti generators state this logic clearly, so it's always unambiguous which value is meant.
Material changes the feel
PLA often feels different from PETG at a tight fit. Differences come from, among other things, toughness, elasticity, surface friction and print parameters. So don't carry the same theoretical clearance value over to every material unverified.
Orientation matters
A round plug part printed horizontally can behave differently than the same part printed vertically. This especially affects roundness, overhangs, layer steps and mechanical load.
Test matrix
For critical fits, a small test series is worthwhile — variant A with little clearance, variant B with medium clearance, variant C with more clearance. The exact values depend on your print system.
Create a custom-fit end cap