Flex Filament Direct Drive Extruder (Max Micron and other Prusa

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Note: Updated ExtruderV4_1 uploaded Feb 9 2017 - some minor changes can improve performance, but also note that tolerances in the filament path are much tighter, so make sure your printer is building very accurately. I've seen many extruder mods for flexible filament, some of which may be better. However, I wanted to design my own and make it a direct swap-out for my stock one. Honestly, it's almost the same basic design with just a few tweaks to get flexible filament to feed better and not curl up or work its way out of the extruder. I also didn't want to have to get more screws and such. • Direct replacement for Max Micron (and most other Prusa i3 clones) • No extra screws or springs needed, use the ones off the stock setup. • Better, more reliable feed into the extruder gear with a longer, better-directed tube in arm • No place for flexible filament to worm its way out of the extruder like it does at times with the stock unit. Notes: I highly recommend using concentric supports if you print with either part flat on their side. About 18% support coverage is recommended. Use at least 3 nozzle widths for shell and at least 1mm top/bottom layering. 15-20% infill works fine as long as the outer shell is thick enough. Add alternating shell with infill if you have it in your slicer. If using ExtruderV4_1, be aware that you can't pull hot filament out because the filament path is very tight with that piece. You need to back out the filament 3-5mm to release from the nozzle and then let cool before pulling through or hot plastic may stick to the extruder's throat and block the next filament from being able to load.