Description
An interactive toy demonstrating the gravitational effects of the black hole, once the object is inside its pull. It roughly follows the "softer" gravity well equation:
z = -A / (r + ε)
The model requires a metal ball to play with :) I used an 11mm ball, but in theory it can accommodate smaller ones and up to 18mm.

Consider printing a test cut of the well first to make sure it's smooth enough inside. For that, move the test model below the plate until only ~1cm is above - to test the settings on the hardest to print area.

Print settings
For everything except the well itself:
* You can go with a standard 0.2mm setting. Brim is not required.

For the well:
The inside of the well is technically a wall; hence, you need to accommodate for that. I printed with HyperPLA and had to reduce printing speed for it to be smooth - perhaps, with regular PLA, you won't face the same problems. That being said, here is how I achieved an adequate result with HyperPLA, but feel free to go slower.
Consider printing a test cut of the well first to make sure it's smooth enough inside. For that, move the test model below the plate until only ~1cm is above - to test the settings on the hardest to print area.

Layer: 0.1mm

First layer: 0.16mm

Seam position: Random (so we don't have a line inside the well)

Wall printing order: inner/outer (the inside of the well is a wall)

Wall loops: 4

Internal solid infill: Monotonic linear

Infill/wall overlap: 20% (can go lower)

Minimum sparse infill threshold: 10mm2

Detect narrow solid infill: OFF (otherwise, it makes circles in the infill instead of lines, which warps a lot)

Speed (feel free to go lower):

* Inner wall: 75mm/s

* Sparse infill: 260mm/s

* Internal solid infil: 175mm/s

* Gap infil: 200mm/s

Acceleration:

* Inner wall: 1000mm/s2

* accel_do_decel: 90%

Jerk XY:

* Outer wall: 10mm/s

* Inner wall: 8mm/s

* Infil: 15mm/s

Brim type: no brim

Assembly:
1. Put the well on the stand. Ensure it is sitting firmly and level to prevent interference with the ball's roll.
2. Put the ball launcher on the column. It goes quite tightly, but it should be okay.
3. Put the metal ball on the launcher and give it a push

Black hole gravity well

0.2mm layer, 3 walls, 15% infill

0.1mm layer, 4 walls, 15% infill

0.2mm layer, 2 walls, 15% infill