This is a modular marble run I created using tinkercad after seeing a similar one somewhere on the internet.. I thought I can make one myself using a 3d printer..
I design the cube to be the main structure to hold on to the tracks so you can make whatever design you'd like..

i use 5mm magnetic balls that is inserted into the cube frames to help snap the cubes together when assembling any design for the tracks..

you could also use clips i design to hold the cubes together if you dont want to use the magnetic balls

The marble run currently only have 5 tracks..

1. slope..
2. straight..
3. double straight..
4. corner turn..
5. u-turn..