Tuesday, August 11, 2009


Simple Pinch-Wheel Extruder Plans

Hi all,

Following up from my recent post [here] about our success with a simple pinch-wheel extruder (made from things around the workshop), some folks suggested it would be a good idea to post plans since the design seems both functional, and doesn't necessarily require any printed parts or precision metal working.

The measurements will depend on the toothed gear and idler pully's that you use -- we don't have any part numbers for ours, since they came from the "random bits we've saved" box. The extruder's DC gearmotor is the same used in the Makerbot Plastruder, which they list as a Kysan 1156006 [Makerbot Partslist] [Makerbot store link].

Here are some illustrations:

And a few pictures that focus on the extruder:

Hope that helps! :)

COOL! Thanks SO much! :-D
Thanks a lot! The extruder is the last piece of the puzzle for me, I've got everything else on my 'Strap working. I was planning on doing a pich wheel extruder, and this looks to be not too hard to make.
BTW, do you have a source for that toothed gear you're using?
the toothed gear came out of something that we took apart -- likely an old plotter or printer or something. we tried to find something in the 'random bits' box similar to the toothed gear that Zach used for the Makerbot plastruder ( a #A 6A51M017DF0306 , 10.3mm OD, 6mm bore, i think: details are in the Makerbot plastruder partslist, that's linked to in the post, or on Zach's blogpost about it: http://blog.reprap.org/2009/01/pinch-wheel-extruder-prototype-v11.html ).

i also managed to measure the extrusion rate: at full speed, the extruder used 20mm of the 3mm diameter ABS filament in about 18seconds. that makes the extrusion volume at about 7.85mm^3/sec. (i'm not sure how that compares to other extruders, i haven't been able to easily google the extrusion rates of other popular extruder designs).

hope that helps! :)
As a benchmark, I get about half that flow rate with the original screw drive and a GM3 gearmotor.
Thanks nophead -- that's really helpful. I e-mailed Zach to ask about the Makerbot plastruder's volume, and here's what he had to say:

Hey Peter,

My partner Adam did some quick tests:

Extruding at ~210 degrees C:
100mm/84.9sec = 1.18mm/sec

Without a nozzle, same extruder, same settings:
100mm/79.1sec = 1.26mm/sec

These are the feedrates of the 3mm diameter filament, not any extruded plastic.

Another simple no-print pinch-wheel extruder variant that I use successfully is very similar to this! I just do this differently:
1 - replace your flat plastic backplane with short length of aluminium angle - ie it's shaped like an L.
2- the vertical section of the L holds the motor just like your backplane, and the horizontal section has a hole/s to bolt the 'hot section' to.
3 - my "transition zone" (ie the PTFE zone) is squeezed between the horizontal arm of the L and the washer-with-three-bolts trick seen in http://farm4.static.flickr.com/3400/3204174499_6af75c3f0f.jpg?v=0

hope my description makes sense. :-)
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