Preset	Cost	Time	Image
C15	~10ct	tbd
C7	~5ct	tbd
S25	~12ct	tbd	(todo)
S10	~5ct	tbd
S5	~5ct	tbd
S4	~5ct	tbd	(todo)
Classic Full Curve (R28 90°)	~25ct	tbd	(todo)
Classic Half Curve (R28 45°)	~12ct	tbd	(todo)
Classic Full Straight (L32)	~20ct	tbd	(todo)
Classic Half Straight (L16)	~10ct	tbd	(todo)
Classic Quarter Straight (L8)	~5ct	tbd	(todo)

You can also generate your own custom rails with any length, radius or angle.

Todo: ramps, switches, train assembly

Design Options

For now, I also use non-baseplate aligned joints for curves. While this means you can't just snap the rails on a baseplate, it enables you to use straight rails at non-90 degree angles which I think is an absolute win over the original design since the 45 degree curves are useless outside of joining them with switches.

Classic

PETG/PVA support interface is mandatory to get satisfactory results

Uses the classic shell design from the injection moulded parts. PETG/PVA supports are a must if you want the part to come out clean!

There's also an option that makes the side studs solid.

Solid

This one is optimized for 3D printing, with the rail solid and flush to the bed. Prints entirely supportless.

Requires additional pieces per rail:

2x printed standoff, these are inserted into the bottom, and need to be fixated there (glue, melting). If you don't use any original Monorail tracks you can also simply place a 2x2 plate there (this changes the height).
8x 4274 (technic pin with stud)

Prints a lot faster than the classic option.

Operating on R25 instead of R28

What difference do these three studs make? With this radius we can take advantage of the pythagorean triples 3/4/5 and 7/24/25 to stay on the stud grid with turntables.

Curve C15
Curve C7
Straight S25
Straight S10
Straight S5
Straight S4

How it fits

Two C15 and one C7 make exactly a 90 degree turn, where every part stays on the stud grid.
An s-curve with C15 moves over 20 studs, diagonals can be done with any length divisible by 5
An s-curve with C7 moves two studs, but diagonals require a full S25 to land cleanly again.

Printing

To be compatible with standard bricks, the following print settings are strongly advised

Nozzle: 0.4, this is equivalent to 1 LDU.
Layer height: 0.2, less than that is barely better and just causes more problems than it solves. If you want to go lower, it's advisable to use heights that satisfy 0.4 % h == 0 such as 0.1.
- Make sure your initial layer height is either 0.2 or 0.4!
Supports: yes, normal, don't use tree supports.
- Multi-material is highly recommended: use PETG or PVA as a support interface layer. This is the only way to get these parts to print cleanly.
Make sure you have your flow and z offset calibrated perfectly. These parts have very small tolerances, it is absolutely vital you have this right or you will end up with parts that have insufficient or too high clamping force.

I print on a modified Voron 2.4 with toolchanger capability through Stealthchanger.

Filament

Color	RAL	PLA Supplier	ABS Supplier
Light Bluish Gray	`RAL 7040`	dasfilament, Prusament
Light Gray	`RAL 7005`

None of these colors will be an exact match, just the texture of 3d printing it can make a huge difference, but usually fall close enough in the range.
The original rails will be in Light Gray, not Light Bluish Gray, but since I barely own any pre- 2004 color change bricks I chose to match my other bricks instead.

Notes for newcomers:

Most bricks are injection molded from ABS, however I find PLA to be much more easy and safe to handle.
PLA starts to deform at 60°C, so don't leave it in the sun or in your car.
PLA is brittle. While ABS deforms with force applied to it, PLA will just snap.
ABS is harder to print, an enclosure is a must, and warping can be difficult to handle.

Printing Safety

In case you are new to 3D printing:

Most filaments (including PLA) can release toxic gases when burned
FDM printing can cause fine particle emission
ABS when heated to normal printing temperatures can release styrene fumes