UPDATE 3: Uploaded the STEP file of the assembly.
UPDATE 2: Beefed up the springs and made them M3 nut trap-compliant. Big thanks to neo0815 for beta-testing with 3mm filament.
UPDATE: I added the version with M3 nut traps. The inserts work well in this piece, but are hard to get outside of US.
Adjustable geared extruder for a printer I'm designing. Designed with E3D hot end in mind, but should work with any standard 16mm diameter hotend. If using it with another extruder, add your own PTFE tube.
Filament: 1.75mm with PTFE tube insert, or 3mm without the tube.
For 3mm, you'll need to widen the top filament guide a little.
Inspired by Greg's Accessible Extruder and this guy: http://www.thingiverse.com/thing:494637
Printed in Colorfab XT, but ABS would work.
Item | Qt
M3x0.5 EZ-Lok Flush Brass Insert | 10
M3x0.5 Set Screw | 1
M3x0.5 16mm Hex Bolt | 6
M3x0.5 20mm Hex Bolt | 2
M3x0.5 8mm Hex Bolt | 3
M3x0.5 25mm Screw | 2 (4 if using bolt hotend retainers)
M3x0.5 Locking nut | 2
608-2RS Bearing | 3
M8 Hobbed Bolt 50mm long, hobbed in the middle (sourced from Lulzbot) | 1
M8 Locking nut | 1
M8 Washer | 2
NEMA 17 Stepper Motor | 1
Insert the PTFE tubing from the bottom and use a blade to slice it off to match the profile of the hobbled bolt guide. The closer you get to the hobbled bolt, the better this will work with flexible filament.
Start with inserting the threaded inserts. You want to push them in all the way using pliers. Try not to damage the plastic. Screw in a bolt into each to expand the inner diameter. This pushes them into plastic and opens up the threads on the other end. The small gear insert is put in from the inside. Use needle nose pliers.
Insert the idler bushing into one of the 8mm bearings, and insert the bearing into the idler. Secure it with an 16mm bolt.
Connect the lock clip to the idler, and connect the assembly to the main block.
Connect the spring tensioners to the springs using the 20mm bolts, then connect the springs to the main block and the lock clip using the 25mm holts. Secure them with lock nuts. Make sure not to over-tighten things. They should be able to swing smoothly.
Press the hobbled bolt into the large gear. Make sure it's pressed all the way in. Add 2 M8 washers. Press in the remaining 8mm bearings into the back and the front of the main block and insert the bolt. Finger-tighten the M8 nut to keep the M8 bolt from sliding off.
Put the small gear on the motor shaft and connect the motor to the main block. Do not tighten the motor bolts until the gears are spinning without too much play. secure the motor. insert the M3 set screw and righten it.
Tighten the M8 lock nut. Be careful not to over-tighten it.
Recommended: Apply a small amount of lithium grease to the gears.
Insert a piece of filament and check the tension. If should grip well, but not grind through the filament.