1:1,000,000,000 Scale models of the planets

Billion-to-one scale models of all eight planets. We had Pluto too, but a map pin was used for this instead of 3D printing.

• The giants (Jupiter, Saturn, Uranus, and Neptune) are printed as two halves, and have a recess for a length of M10 threaded bar to be epoxied in. This is used to mount the planet to a display board, with the metal shrouded in some black heat shrink wrap. They also have holes for fitting 10mm wooden dowels inside to aid alignment of the two halves, which were also glued together with epoxy.
• There are a series of holes in Saturn. These are for cut off bicycle spokes to be inserted to support the rings, so they're at 26.7º to the ecliptic. The rings themselves were designed in three segments, and printed in transparent PLA, and include the major ring elements. These where then bonded together with epoxy via a lap joint, and this was overlaid with some fibreglass on the underside to give it a bit more strength. There are clips to glue the rings to the bicycle spokes - print these in transparent PLA too.
• The larger rocky planets (Venus, Earth, and Mars) are also in two parts, but as they're so small each of the two halves just mounts onto a length of 3mm diameter glass fibre rod.
• Mercury was printed as single piece, with a mounting hole towards the print bed. You'll want a brim and a bit of luck. A bicycle spoke was used for mounting this one.

Once printed, each model was assembled, then sanded and painted. We used an initial spray of a good thick automotive primer and a bit more sanding, before hand painting in acrylic. For Saturn, the planet itself was first painted, and then the rings were assembled.

I printed all the planets in a grey PLA on an Ender 3 S1. For the giants, I basically went as corse as the printer would go (0.28mm layer height?), and obviously the smaller the planet, the finer the print resolution had to be.