Fully Printed Optical Filament Sensor

This all printed 1.75mm filament sensor with optical endstop. All Parts are printed (except endstop itself of course). Works with transparent filament and unidirectional. Haven't been tested for reliability yet. I printed it with PLA but should work with PETG, but I did not try yet.

Biggest benefit of this solution is very low resistance to filament moving I mean comparing it with switch based filament sensor sold on Amazon. At least one I got there is quite resistive to filament movement comparing to this one. Theoretically as resistance is low it should not wear for long time, but needs validation in practice.

I used HESAI optical endstop from [Amazon](https://www.amazon.com/gp/product/B0719K9Z9R/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) but I believe it should be quite generic.

For this sensor plugged into regular endstop and SKR v1.4 board setting for FIL_RUNOUT_INVERTING is false. I beleive for v1.3 it should be the same.

Update:

case_btm.scad - added some pa