Make sure you print a few test pieces before one of the large plates; some people have reported that the default tolerance is too large for them and the track won't snap together. Change the tolerance variable in the customizer to .20 or .15 to make the fit on the pieces slightly tighter!
This is a set of modular marble track pieces that work well with 3/8" bearings (or other similar, small marbles.) By default, the track "unit" is 20x20x20mm; the open pieces of track are half-height, and the drops are double height. Print it out and use it (like I have) to avoid whatever important work you're supposed to be doing.
- the OpenSCAD file (which is parametric, and should work now),
- two track set STL files (which are about 160x160, so should print on an i3)
- individual STL files for each piece in the standard sets
- an 8mm marble (which probably needs a raft/brim, and may not be heavy enough)
Updated on 21 Apr 2017: The .scad file now has better support for parametrization; if you use Thingiverse's customizer, you'll get a full set with one of each piece, which should make changing/remixing easier. I also squished the pieces together a little more in the track sets, which should reduce print time a little.
Prints well at 40mm/s and .3mm layer height on my cheap i3 clone. The pieces have (by default) .25mm of extra lateral room at the connectors; if your printer is nicer than mine, you might need to change this in the OpenSCAD file and re-generate the pieces / track sets.