This is an optimized version of the "Mechanical Planetarium" model by Zippitybamba. His original model is on Thingiverse here: [https://www.thingiverse.com/thing:4613061](https://www.thingiverse.com/thing:4613061)

I printed a few parts of the original model on my Prusa I3 MK3S, and I wasn't satisfied with how they fit. This sent me down a rabbit hole of refactoring and tuning the file until I could print it with insanely low tolerances of about 0.12mm on average.

The original model is truly excellent and deserves to be on the main page for a long time. I put in a lot of time tuning this, so I thought I should share what I've done.

A quick summary of edits:

• Combined the base and upper mechanism into one file.
• Added toggles for rendering each object.
• Refactored source for ease of reading and editing.
• Switched to the English fork of "Getriebe.scad" named "Gears.scad". Translated by Chris Spencer. [https://github.com/chrisspen/gears](https://github.com/chrisspen/gears)

• Added several customizer sliders to:

  • Compensate for printer Z thickness.
  • Control spacing for meshing of the gears in the base.
  • SCALING! The model is scalable between 50-150% on the X and Y axes only. Object Z heights are controlled separately. Tolerances are corrected so they don't change as you adjust the overall scale. (Scaling to 90% will make it fit on a Prusa Mini)

• Adjusted the length of the Venus planet arm (by 1mm) so the peg doesn't collide with the idler wheel above it.

• Tightened everything up so it could be printed on a well calibrated machine with very minimal post-processing. I only needed to smooth out bits on the top layer due to filament retraction.

I also wrote a quick Windows Batch file to generate all 47 files. A word of warning; It will absolutely hammer your processor since it opens a separate copy of OpenSCAD in the background for each file. If you know your way around OpenSCAD, then I'm assuming that you know how to read and use a batch file. "Here be dragons."

Update: I identified a small issue with the inner pegs on the Calendar Gear. They were protruding 0.1mm above the center bearing. This would not be an issue for 99% of people printing the model, but I fixed the file and posted an update. If you're printing at anything larger than 100% or a layer height below 0.2mm, take a look at your preview.

Update 2: I fixed an issue with non-uniform scaling of the printable planets in the SCAD file.

All credit for this design belongs to Zippitybamba. All I did was clean things up and tweak a bunch of things.

Print instructions

Print Settings

Printer Brand: Prusa
Printer: I3 MK3S
Rafts: No
Supports: No
Resolution: 0.4mm Nozzle. Layer Varies: 0.2mm and 0.25mm
Infill: 15% Grid
Filament: Prusament, Mika3D, and Sain Smart PLA

Notes:

I generally used three perimeters for all objects with the exception of the Mercury Axle. I used five perimeters for that so it would print essentially solid with no fast infill moves. I split the Mercury Axle in half and printed it vertically one piece at a time. I joined the halves using a small piece of aluminum rod that I wedged into the hole in the middle.

I also tweaked my perimeter extrusion widths extensively so it would always print full perimeters. In PrusaSlicer it's on the "Advanced" tab under "Print Settings". I adjusted the "Perimeters" and "External Perimeters" while checking the preview until the white "Gap Fill" was replaced with a yellow perimeter.

Watch out for Elephant's Foot. If you're using PrusaSlicer, go back into your Advanced Print Settings and adjust the "Elephant foot compensation" until you have a crisp bottom edge.

If you use Cura, or some other slicer, poke around in your settings and look for similar options.