With mating parts, you’ll have to design them so that even with the uncontrolled error in the dimensions, they will still work together as designed. In almost all cases this will mean that if you have two parts that should fit together, you’ll need to design one part smaller than the other. For a standard 0.4 mm nozzle, here are general rules of thumb for fits based on a hole and shaft join, although you’ll have to experiment and learn the actual values for your printer.
•Clearance fit: A difference of 0.5 mm and above between the diameter of the hole and the diameter of the shaft. This results in a theoretical gap of at least 0.25 mm between the shaft and the hole.
•Transition fit: A difference of 0.15-0.4 mm between the diameter of the hole and the diameter of the shaft. This results in a theoretical gap of 0.08-0.2 mm between the shaft and the hole.
•Interference fit: A difference of around 0.1 mm or less between the diameter of the hole and the diameter of the shaft. This results in a theoretical gap of 0.05 mm or smaller between the shaft and the hole.
•Because these rules relate to the difference between the parts, they can also be used for non-cylindrical parts. When considering non-cylindrical mating parts, like a square hole and a corresponding square protrusion, the above-mentioned rules may apply to the difference between the closest planes of the mate. For example, to get a clearance fit for a 30 mm square rod, design the hole so that a gap of 0.25 mm is maintained (i.e. a 30.5 mm square).