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109 lines
5.8 KiB
Markdown
109 lines
5.8 KiB
Markdown
# Brick Monorail
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Parametric Lego-compatible monorail tracks, designed specifically for 3d printing.
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Two orders of magnitude cheaper than buying used.
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Since the parts are made parametric, you can have any length or curve radius you want,
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but these are the original tracks you can replicate
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As an overview, or why it's worth a try: They print rapidly on modern printers, and cost barely anything.
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| Preset | Cost | Time | Image |
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| ----------------------------- | ----- | ---- | -------------------------------------------------------------------------------- |
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| C15 | ~10ct | 45m |  |
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| C7 | ~5ct | 15m |  |
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| S25 | ~12ct | 1h |  |
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| S10 | ~5ct | 15m |  |
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| S5 | ~5ct | 15m |  |
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| S4 | ~5ct | 15m |  |
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| Classic Full Curve (R28 90°) | ~25ct | 2h |  |
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| Classic Half Curve (R28 45°) | ~12ct | 1h |  |
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| Classic Full Straight (L32) | ~20ct | 1.5h |  |
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| Classic Half Straight (L16) | ~10ct | 45m |  |
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| Classic Quarter Straight (L8) | ~5ct | 15m |  |
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You can also generate your own custom rails with any length, radius or angle.
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Todo: ramps, switches, train assembly
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## Design differences
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Injection molding has vastly different requirements to 3d printing.
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Due to this the original rails print absolutely horribly due to the copious amounts of supports needed.
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Surfaces printed on supports just never look good.
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Because of that, I decided to instead of having a support part on the bottom, I'd carve out space for
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a 1x2 plate, which you can fit there for the same effect.
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The monorail tracks are also solid now, which is not something you can do in injection molding but leaves
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a really nice surface finish at the bottom of the rail for us.
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For now, I also use non-baseplate aligned joints for curves. While this means you can't just snap the rails
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on a baseplate, it enables you to use straight rails at non-90 degree angles which I think is an absolute
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win over the original design since the 45 degree curves are useless outside of joining them with switches.
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_These are 3d printing optimized, compatible rails, not replicas. Replicas print horribly due to support._
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### Optional Differences
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#### Operating on r25 instead of r28
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What difference do these three studs make?
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With this radius we can take advantage of the pythagorean triples `3/4/5` and `7/24/25` to stay on the stud
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grid with turntables.
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- Curve C15
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- Curve C7
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- Straight S21
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- Straight S7
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- Straight S6
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- Incline I4
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How it fits
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- Two C15 and one C7 make exactly a 90 degree turn, where every part stays on the stud grid.
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- An s-curve with C15 moves over 20 studs, diagonals can be done with any length divisible by 5
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- An s-curve with C7 moves two studs, but diagonals require a full S25 to land cleanly again.
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## Printing
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To be compatible with standard bricks, the following print settings are strongly advised
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- Nozzle: **0.4**, this is equivalent to 1 LDU.
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- Layer height: **0.2**, less than that is barely better and just causes more problems than it solves.
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If you want to go lower, it's advisable to use heights that satisfy `0.4 % h == 0` such as 0.1.
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- **Make sure your initial layer height is either 0.2 or 0.4!**
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- Supports: **yes**, normal, don't use tree supports.
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- Set your "Initial Layer Horizontal Expansion" to a value that works for you, for example -0.2mm to compensate for elephant's foot.
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Alternatively, you can trim the extra plastic off by hand.
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My prints were done on a modified SecKit SK-Go2 running Klipper, with 10k acceleration and 150mm/s print speed for a good
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balance of speed and quality. A short rail will take about an hour to print.
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### Filament
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| Color | RAL | PLA Supplier | ABS Supplier |
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| ----------------- | ---------- | ------------ | ------------ |
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| Light Bluish Gray | `RAL 7040` | dasfilament | |
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| Light Gray | `RAL 7005` | | |
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- 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.
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- 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.
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_Notes for newcomers:_
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- Most bricks are injection molded from ABS, however I find PLA to be much more easy and safe to handle.
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- PLA starts to deform at 60°C, so don't leave it in the sun or in your car.
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- PLA is brittle. While ABS deforms with force applied to it, PLA will just snap.
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- ABS is harder to print, an enclosure is a must, and warping can be difficult to handle.
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#### Printing Safety
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In case you are new to 3D printing:
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- Most filaments (including PLA) can release toxic gases when _burned_
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- FDM printing can cause fine particle emission
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- ABS when heated to normal printing temperatures can release styrene fumes
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