Customizable Air Trimmer
Suitable for holes starting at 30mm. I've used this design to regulate the airflow of a 3d printer enclosure. Perfectly circular holes are easy to make using a cheap hole saw set.
The aperture with this design is always 0-48% of the hole size (50% for the blades minus the centerpiece), regardless of the number of slices. The cap needs to be pressed into the support until it clicks in place. It is recommended to fit the cap before inserting the trimmer into the hole.
Needs OpenSCAD (or the Customizer) to regenerate. I included some pre-generated models for common metric and imperial hole sizes. The hole depth is 15mm (~0.6in), but can be easily cut to a shorter length in your favorite slicer without having to install OpenSCAD.
The default wall sizes are optimized for a 0.4mm nozzle and 0.2mm layer height.
Consider thickening the cap height for holes >100mm.
Update 2019-01-06
The author remixed this model. Imported from Thingiverse.
Now parametric