D-Bot Fully-Supported Extruder

This is a from-scratch redesign of the D-Bot extruder. I'd had issues with high filament pressure when printing very quickly causing the filament to bow out and either break or wrap around the hobbed gear, plus I want the option to use softer filaments with the D-bot.

This extruder design keeps PTFE support tubes in very close proximity to the bearing and hobbed wheel, so there's no possibility of filament bending out of the extrusion path.

The hardware needed to assemble it is pretty basic:

MK8 extruder gear (from the stock extruder)
625ZZ bearing (from stock extruder)
3x M3 8mm bolts (from stock extruder)
6 M3 washers
3x M3 30mm bolts
2x M3 nuts
Small length of 4mm OD/2mm ID PTFE tubing
2x M3-sized tensioner springs. (There are good options in the set of springs from Home Depot that is called out in the D-Bot parts list -- generally you want a somewhat stronger, small spring about 5mm in diameter, 20mm long, so it can compress down to 12-13mm)
Bowden connector (fro