Update 04/26/2016: I will not modify this design anymore, there is a STEP file attached, feel free to alter the way you like.
Update 02/09/2015: Refreshed all stl files to match latest CAD file. Older stl files removed, use DS Mechanical to open older source files if needed...
Update 28/08/2015: Now tested with TPE (flexible filament). Uploaded new DS Mechanical file (v12) with new gears, if you are using old ones - leave it as is...
Update 28/07/2015: Left a bit more space for idler bearing, still there is a small chance that you'll need to cut some plastic during assembly to get a good grip.
Easy filament change quick release geared bowden extruder. Just push the idler arm and pull filament outside, then insert new one and release. That's it! Gear ratio is 1:3.54, for 1/4 microstepping and 1.8 degrees stepper it's 150 steps/mm.
- 6x 10mm M3 allen head bolts
- 2x 30mm M3 allen head bolts
- 4x M3 hex nuts
- 1x 50mm M5 hex head bolt (axis)
- 6-8 M5 washers
- 1x 30mm M4 bolt, at least one M4 hex nut, some M4 washers to adjust spring tension
- ~ 25mm spring
- MK8 gear for driving filament
- 2x 625ZZ bearings
- 1x 608ZZ bearing
Works fine with ABS/PLA/Nylon/TPE (http://www.youtube.com/watch?v=9IM2rGlbEXE, http://www.youtube.com/watch?v=E93ouMbCUXw).
Print all parts, no support needed. I used both ABS and PLA, PLA seems to be better choice. Idler should be printed vertically, shorter part is below. Put axle inside the 608ZZ bearing, put both inside the idler. Once you put the axle and bearing inside the idler they cannot be extracted back. Put one 625ZZ bearing to the back side of the main body, thin support cylinder in the hole can be removed easily prior to pushing the bearing.
Put one M3 nut to the hole in the smaller gear, attach the stepper to the extruder body, put the gear on stepper axis, put one M3 bolt to the hole in the gear to make it sit tight on stepper axle. Push M5 hex bolt to the larger gear, add two washers on opposite side of the gear, attach to the extruder body. Put more washers after the 625 bearing (4-6), put MK8 gear to the M5 bolt, make sure it sits right, tighten it. Check if stepper rotates larger gear, if it rotates smoothly then you can put other 625 bearing to the front side of the extruder.
Put two M3 hex nuts to the back side of the extruder, use lower M3 nut and 30mm M3 allen bolt to attach a strut to the extruder body. Now use M4 bolt to attach a spring to the extruder. Use nuts and/or washers to provide proper load on the spring. If the spring doesn't have enough load then MK8 gear won't get enough grip. Now put idler on the extruder body and use upper M3 nut and 30 mm M3 allen head bolt to fix the idler in place.
Use ~100 mm piece of filament to check the load on spring and grip on the MK8 gear. If there isn't enough grip on the gear then detach the idler, add more washers to the M4 bolt, attach the idler back. Give it a test run, print a simple thing to make sure filament doesn't slip on the gear. If nessesary change the load on the spring again. After the load is set properly there is nothing to adjust anymore, just press the idler arm to change filament.