[2014-07-02] Added a configurable fan duct (preset for a long nozzle).
[2013-09-13] Fixed supports, bottom-width, outlet hole alignment, 25mm motor bolts.
[2013-09-11] Added an optional nozzle stabilizer, fixed the body groove
[2013-08-24] Wider idler hinge, better supports, longer endstop bumper.
About Tweety Extruder
Gain a little extra height on your Prusa i3 with this simple direct drive extruder. Requires an inverted "mini" x-carriage or you can use the "Universal 24-to-30mm GT2 X-Carriage" http://www.thingiverse.com/thing:135353, also included here.
My one previous attempt at an extruder was the Compact Extraptor http://www.thingiverse.com/thing:120971 and as a conglomeration of extruder and mounting part it's pretty good. But it requires long back-to-front screws and was kind of bulky. With Tweety I started the code over from scratch, centering everything on the filament pinch point, and made it possible to use shorter M3 screws.
The optional "nozzle stabilizer" was added to limit how far the hot-end may be pulled downward if it collides with an object while the Y bed is moving from front-to-back. This is a weak point of vertical x-carriage setups like the i3. The nozzle acts like a lever, pulling the assembly downwards. For this reason most fatal "head crashes" occur when the bed is moving in the minus-Y direction. By limiting the movement of the hot-end closer to the platform, the stabilizer should improve reliability in cases where a rising overhang or small blob could sabotage a whole print.
The SCAD, and the STLs included, are set up for a 2engineers 50:1 geared stepper motor, MK7 filament drive gear, 3mm filament, and a 608 idler bearing. The SCAD is highly parametric, so it should be relatively easy to adapt for your specific motor and dimensional preferences.
Print the parts, then connect them in the following order:
- First: Insert M3 locknuts deep into the nut traps in the extruder body.
- Assemble the idler with the axle and a 608 bearing.
- Attach the idler to the body with an M3x20mm bolt or 3mm filament.
- Add idler tensioner shoulder bolts, 2x M3x30mm, with nuts
- Attach the motor to the body with 2x M3x25mm bolts
- Insert the hot-end into the extruder.
- Add a short M3 bolt to the fan mounting hinge.
- Attach the fan to the fan mount or fan duct.
- Attach the hot-end clamp and fan mount with 2x M3x30mm bolts.
- Attach the assembled extruder to the x-carriage with 3x short M3 bolts.
Customizing the SCAD
This SCAD has lots of tunable parameters. You can change the filament width, motor size, idler axle offset, mounting height, and much more. Most parameters can be altered and produce a usable object, but there may be a few that create some weird results. Experiment and let me know if you need help.
As usual, all the parts that will come into contact with the hot-end must be printed in ABS (or any heat-tolerant material).