feat: end cap

README.md

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+# Parametric Monorail
+
+## Design differences
+
+Injection molding has vastly different requirements to 3d printing.
+Due to this the original rails print absolutely horribly due to the copious amounts of supports needed.
+Surfaces printed on supports just never look good.
+
+Because of that, I decided to instead of having a support part on the bottom, I'd carve out space for
+two stacked 1x2 plates, as well as a special two-high printable brick you can use for compatibility with the
+old support mounts.
+
+_These are 3d printing optimized, compatible rails, not replicas. Replicas print horribly due to support._
+
+## Printing
+
+To be compatible with standard bricks, the following print settings are recommended
+
+- Nozzle: 0.4, this is equivalent to 1 LDU.
+- Layer height: 0.1, though 0.2 will also do. Refrain from using 0.15, since that does not cleanly divides the LDU.
+- Supports: Tree (normal supports may print faster, but lead to way worse results. But ymmv).
+
+My prints were done on a modified SecKit SK-Go2 running Klipper, with 10k acceleration and 150mm/s print speed for a good
+balance of speed and quality. A short rail will take about an hour to print.
+
+### Filament
+
+| Color             | RAL Color  | Pantone | PLA                                                                                                         | ABS |
+| ----------------- | ---------- | ------- | ----------------------------------------------------------------------------------------------------------- | --- | --- |
+| Light Bluish Gray | `RAL 7040` |         | [dasfilament 20,56€/kg](https://www.dasfilament.de/filament-spulen/pla-1-75-mm/8/pla-filament-1-75-mm-grau) |     |
+| 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.
+- 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) release toxic gases when _burned_
+- FDM printing can cause fine particle emission
+- ABS when heated to normal printing temperatures can release styrene fumes