To tell the truth, I really wanted to cheat when making this part this past weekend. Greg's extruder is now so well tuned, that it will probably be one of the first upgrades I'll print myself when my repstrap goes on line.
But, it is all about the journey. And I had lots of fun hacking this extruder together
I do not expect anyone making this thing, but here are instructions for the foolish, or the brave (or possibly both)
1) Get a nice strong Maranti decking plank cut-off, and cut 2cm off one side (you have to cut twice to get it squared off)
Open Greg's extruder scad file, modify it to match your hot-end, and keep as reference.
2) modify the 2cm piece you just cut to match the hot-end configuration on screen.
3) Cut another piece of 8cm from the decking plank.
4) Place it on end on the 2cm piece, and mark the hot-end filament feed hole.
5) Using the large gear as guide, mark and drill though the plant to secure the center of the gear shaft using a small drill bit (4mm)
6) Use a 20mm flat wooden drill bit, drill into both sides, leaving a 1cm center piece - it will depend on your plank thickness.
7) drill though using 10mm drill bit.
8) From center of the shaft, mark 45deg to the bottom front (right) of the gear shaft, and from the shaft straight up. Cut.
9) Use M8 threaded rod, or bolt, and mount the large gear to the shaft placing two 608 bearings in the 20mm bearing holes.
10) Place Stepper motor with small gear attached next to the large gear to mark its position. Place it as shown in the photo.
11) Cut 45deg next to the motor mount the reduce weight, and then recess the motor into the plank to align the gears.
12) Glue the newly created piece on the 2cm piece using your favorite cold wood glue.
13) Mount the large gear - you may have to recess the bottom piece around the gear.
14) Cut slot for lever in base of extruder. Create lever using whatever you have available - I used plywood. See photo. The 608 idler is held in place with a piece of M8 rod, and the lever held onto the shaft with a spring. The arrangement of this will change...
15) Mark the drive shaft, and hob it using your favorite method. I used the tapping bit in a drilling machine way.
The gears I had available gives me a highish ratio of 5. The small stepper I had laying around will not suffer too much ;-)