A press fit needs to hold on its own, without extra hardware
Unlike a sliding or rotating clearance fit, a press fit is designed to grip: the shaft or pin is deliberately made slightly larger than the hole, so the material itself deforms elastically on assembly and holds the joint together by friction. Too little interference and the joint is not really retained; too much and it either will not press together or cracks the surrounding plastic on assembly. This is a narrower target than a clearance fit, which is exactly why a staged calibration approach matters more here.
How the plan works
A material-specific exploratory interference range is offered as a starting point, generally tighter for rigid materials and looser for TPU, if you have not yet measured your printer's actual behavior. If you have a measured interference value from your own calibration, it is used directly instead. Either way, the output is a planning dimension for the shaft or pin against a fixed nominal hole, explicitly not a guaranteed retention force.
Worked example
An 8 mm nominal shaft in PETG, no measured interference supplied: the tool suggests designing the shaft near 8.15 mm (midpoint of the 0.1 to 0.2 mm exploratory range) and recommends printing a staged set of test pins across that range to find where the fit actually transitions from loose to properly retained to too tight to assemble.
A common mistake
A frequent error is testing an interference value once at room temperature and assuming it holds regardless of how the assembled part is later used. A press fit that grips well at room temperature can loosen if the part sees regular heat cycling, since the two mating surfaces expand and contract slightly differently over time. For a part with real thermal exposure, test under those conditions too.
Limitations
This is a planning interference for your CAD model, not a guaranteed manufacturing tolerance or a calculated retention force. Confirm fit and holding strength on a printed test piece before committing a design that depends on a reliable press fit.