Flexion HT Extruder for the Prusa i3 MK2S

Version history:
- v2.0 - Extra Chub - March 9th, 2018
Changes and fixes:
- Self-tapping fan screw holes no longer require hulk-like strength to screw into.
- Alignment and tolerances for mounting the stepper and extruder are improved and much tighter.
- Overall strength and rigidity has been improved at the cost of a bit more material and print time.
- Better cable management options and a slot for a zip tie to hold stepper cables.
- Even better thermal performance. The heatsink is now fully ducted, forcing the cold end cooling fan to pull in significant quantities of air from beneath the heatsink, over and through its cooling fins, before finally exhausting the now-hot air out and away from the print head.

- Blower fan nozzle height has been tweaked for better aiming of the air flow at the area immediately beneath the nozzle.

- Y-axis print area loss has been reduced to 10mm.
- Stuff that I've forgotten about still changed, but may not be on this list :).
- v1.0 - December 19th, 2017
- Initial release

IMPORTANT: The Prusa/E3D hotend cartridge thermistor does not fit in the Flexion hot ends. You can use a NTC 3950 100K Thermistor as a drop-in replacement however - your MK2S will never know the difference.

This is a complete extruder and hotend holder design that allows you to mount a Flexion or Flexion HT for i3 style printers for use with your Prusa i3 mk2/s. No special hardware is needed, you can reuse the fasteners you'll obtain from the old extruder body.

I've attempted to make this feel as 'native' to the mk2s as possible, to the point that you can even use the original fan nozzle. It mounts on the stock x-carriage and no parts need to be altered or swapped out, save for the extruder body and extruder cover.

The convective paths for air cooling have been planned carefully, and you should be able to access the full temperature range of the Flexion HT hotend without any plastic parts sagging or deforming even when using PETG.

There is one caveat, and that is that you will lose 12mm of build area along the Y-axis. This is, unfortunately, unavoidable due to stepper motor clearance issues on the extruder. Personally, it's a small price to pay. To compensate for this, see the final step at the end of this page/assembly guide.

Compatible with the regular Flexion as well as the Flexion HT upgrade. Single extruder only. NOT for the E3D version of the Flexion.

If you've been using one of the Noctua hotend fan upgrades, then by all means, continue to use it! :D They should be totally compatible with this new extruder.