I wanted a bomb-proof extruder so I can print fast and reliably, so I hand-made one. That's the plan anyway...
I will of course print one of Adrian's new Mini extruder's and have a go at using a NEMA11 motor in a Bowden configuration at some point, but for now here is how this one was made and assembled.
Top shows the filament drive path and Pneumatic Push-fit connector for standard 4mm or 6mm PTFE tube.
Middle is Idler bearing block.
Bottom right is Nema17 motor mount.
Close up of Pneumatic connector - tapped and screwed, PTFE tube can easily be fitted and removed.
I decided on a 10mm belt-driven drive-train (belt is 280mm) Pulley's are 16 and 40 teeth.
I wanted a straight-through filament drive so it's easily mounted on my RepStrap and could be made to tilt as printed build-height increases.
Underside - Excessive use of bearings for a belt-tensioner I know.
I mounted the 4 springs recessed inside the bottom block, so I can just use normal wing-nuts on the top idler block, this makes it much easier to take apart to clean and reduces the total height by using dead space for the springs inside the extruder body instead of sticking out the top.
This has 3mm ABS coming out of the 6mm Push-fit Pneumatic connector, but it's just as easy to screw in a 4mm for 1.75mm Filament drive.
I'm sure this design could easily be printed so If it all works well I will try to print a copy of itself and post some design files. And I really like the Herringbone Gears, so I expect that will replace the belt-drive in a printed model.
I also think the internal compression springs idea could be incorporated into other extruder designs, it really makes filament change and cleaning a much easier job than having to remove the springs each time.
I have also made a new 1.75mm hot-end for this Bowden driven Extruder, I'll post that and how I made it tomorrow.