Single layer model that is useful and takes 43 seconds to 3Dprint
I have 3Dprinted few layer models before, eg. very lightweight airgun pellets for supersonic shots:
https://forum.prusa3d.com/forum/english-forum-awesome-prints-hall-of-fame/3dprinting-supersonic-speed-airgun-pellets/#post-593293
Today I removed the autofocus of a (newly bought, 2nd NoIR) Raspberry v3 camera.
I did that because its Sony imx708 sensor is light sensitive and good for astro photos (12 seconds exposure).
See postings starting here and following — cropped animation shows 2nd starlink satellite I captured:
https://forums.raspberrypi.com/viewtopic.php?t=348014#p2086185 
Plan is to add that camera to my cheap telescope for eyepiece projection like I added Raspberry HQ camera here:
This is v3 camera with autofocus removed:
I did need to superglue a CStoC metallic adapter ring onto the camera PCB centered wrt. image sensor.
Therefore I 3Dprinted single layer ring just fitting inside with a centered cross.
The width of cross needed to be 0.43mm, otherwise PrusaSlicer did not create it with 0.4mm nozzle.
The ring is fixated by CS lens screwed into adapter ring.
The OpenSCAD model and STL file are here, as well as more details:
https://www.printables.com/model/453158-single-layer-cross-for-centered-adjustment-of-lens
I was not able to attach the 43 seconds print Prusa MINI+ .gcode file, obviously the website does not think such a small file can be useful.
(I had problems getting single layer print off the print bed, but it was good enough for the task)
I had to dremel away a bit of the metallic ring (for the imx708 sensor connector) to make it fit onto camera PCB.
This is complete camera after superglueing centered with the help of the cross and camera preview on HDMI display: