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Customizer Push-me-pull-you Extruder Drive

by chowderhead, published

Customizer Push-me-pull-you Extruder Drive by chowderhead Feb 3, 2013

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I'm potentially faced with producing scads of copies of prints and need a way to increase productivity of the printer. This extruder drive uses a regular 'ol hobbed bolt and pushes two 1.75mm filaments simultaneously. It will be attached to a pair of these rocking awesome x-carriages: http://www.thingiverse.com/thing:45883, each fitted with a 1.75mm x 0.35mm J-head hot end. The carriages will be placed on the x axis, splitting the build volume equally between the two hot ends.

My thoughts are that I'll halve the x dimensions of the printer build volume in Cura, making plates of parts that will build in a 100mm x 200mm x-y space. Duplicate parts should be produced on the printer twice as fast as I've been able to in the past.

This does work, at least with a single filament, which is all I can test with at the moment.

The rub is that I only have a single J-head at the moment and I'm desperately hoping someone better equipped might want to help me out and test this thing...


02.13.13 - changed the Customizer code to only render extruder end, idlers and caps, the motor end is now an stl. Changed the motor end to have beefier rod mounts as I snapped the wimpy original ones off. Some other structural mods to the motor end to improve printing and strength.

Several prints have now been produced and experience thus far is good. Plugged up the hobs and had to clean them out and printed idlers having a bit more spring stretch to try and combat that issue, will update as experience permits.

The 1" x 9/32" (od) x 0.047" (wire diameter) springs on the one pictured work great with hard PLA but squish ABS too much. I'm looking for the right spring for ABS.

Measure the distance from bolt head (the inside where a washer would go) to the center of the hob and enter this value for Cap To Hob in the Customizer. Enter your spring dimensions in the Customizer. In Customizer, render one each of Extruder end and Idlers and caps and print at 100% infill.

Print gear_sun.stl, input_half.stl, output_half.stl, output_carrier.stl and planetgears.stl.

There are two M3 nut traps in the interior of the extruder end where the hobbed bolt passes through. Carefully press an M3 nut into each before proceeding.

Assemble the gearbox per http://www.thingiverse.com/thing:41876 using the hobbed bolt for the output shaft. Make sure all four M3 nuts are in the extruder end (four holes on the pedestal - nuts pressed into interior side) so that idlers and springs can be mounted.

The extruder end requires:
3 each 608 bearings
2 each of M3 x 30mm screws, M3 nuts and M3 washers for mount-side spring mounts
2 each of M3 x 16mm screws and M3 nuts for idler-side spring mounts
2 each of M3 x 30mm screws and M3 washers (between idler and end) for idler pivots
2 each of M3 x 16mm screws and and M3 nuts for mounting in-out caps
2 each M4 nut for Bowden sheath lock
2 each 8mm diameter x 16mm smooth rod for idler shafts
1 each M8 nylon locking nut
2mm id x 4mm od PTFE (teflon) tubing for Bowden sheath

1) Put the 608 bearings and their shafts in the idler holders.
2) Push the spring ends into the idler holders and run the M3 x 16mm screws through them and tighten into the nuts (traps provided)
3) Use the 30mm M3 screws to attach the idler holders to their pivot points (the idler shaft is exposed) with a M3 washer placed between the extruder end and the idler holder
4) Put the M3 x 30mm screws through the other ends of the springs, spin on a nut and then a washer and thread the screws into their holes in the extruder end.
5) Push the PTFE tubing through the appropriate hole in the in-out caps (has the M4 nut trap in it
6) Thread the M4 nuts onto the ends of the 4mm PTFE tubing, trim and ream, make sure 1.75 mm filament can freely pass through
7) Affix the caps to the extruder end with M3 x 16mm screws.

Take a picture and show me you built one!

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Very interesting design! I just had a midly similar idea, so I decided to poke around on Thingiverse and see what else I could find like it. My idea isn't for bowden extruders, so it will have to have 2 separate drive gears hobbed into the bolt.It will also include a rocker arm mechanism actuated by a 5V solenoid to select which filament is being driven, meaning it will only be able to extrude 1 filament at a time.

This design works incredibly well, but I abandoned it to pursue something similar to your suggestion. Still only one hob, but servo controlled to activate the desired filament...

Have you seen this?
Though it is for switching dual head extrusion in one print, it is not that far from your concept.

Yeah, I saw that. Really sweet how they want to patent it. Wait until I put the the new PMPY extruder drive with servo selection of filament up with a sweet CC-By SA and NO PATENT!

Take a guess what I think of their kickstarter project...

I did think that it was "odd," for lack of a better word, that they would patent their idea on top of opensource ideas. Five second later I realized their patent would mean nothing and a clone would be thingivers soon.

It made me chuckle and then I thought of your one motor dual extruder...

nice idea
only thing i see is, eventual grinding dust will fill the idler wheel twice as fast.
is it easy to open and clean?

Not so easy with these 0.047" wire springs. Haven't got my second hotend yet to shake the thing out - bound to be teething issues.