ArmDrive Bowden Extruder

by ChiggerPepi, published

ArmDrive Bowden Extruder by ChiggerPepi Feb 10, 2014
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The ArmDrive is a 1.75mm filament bowden extruder, designed to work with the NEMA 17 stepper motor. It mounts directly to any OpenBeam or equivalent sized (15mm) extrusion. With the complimentary mounting bracket, it can also be attached at a 90° angle. The optional bracket is located here: https://www.thingiverse.com/thing:2353189

The MK7 and MK8 versions are each designed to work best for those particular drive gears, or gears with similar dimensions.

The extruder is designed to be robust and reliable, while using as much easy to find hardware as possible.

These files are the result of a surprisingly large amount of work, I hope you find they work as well for you as they do for me.


Update - January 6th 2015

Revision 2

  • Slightly increased the diameter of the post holding the 608ZZ bearing to reduce play and allow more clearance around the outside of the bearing near the swivel shaft area.

  • Increased the radius of the bearing cutout near the swivel shaft area by an additional .2mm to allow for more clearance for problem described above.

  • Significantly strengthened the input filament alignment post.

  • Added more support behind the spring retainer arm on the base-plate to reduce warping over time when under high spring tension.

  • Increased height of the three standalone posts on the base-plate by .2mm to allow for more torque when installing the screws without causing the binder arm to jam.

Update - October 24th 2015

Revision 3 is now available!

  • Increased the rigidity of the upper and lower arm segments in response to feedback about occasional cracked and broken arms.

Update - May 29th 2017

  • I have designed a 90° mounting bracket to make alternate angle installations a breeze.



The ArmDrive was designed to be printed at .2mm layer heights, any other setting may result in less accurate vertical layering.

Suggested print settings:
Layer height: .2
Perimiters: 4
Solid layers Top and Bottom: 4
Infill: .4

ABS plastic is highly recommended. PLA will work in a pinch, but tends to warp over time, especially due to heat created by the NEMA 17 stepper motor.

Drill bit sizes: (confirmed working)
15/64" for the upper and lower arm pivot holes
1/8" for all screw holes excluding the lower arm
7/64" for the two lower arm screw holes

I don't have any metric drill bits for testing, but the hole diameters once drilled should be approximately:
6mm for the upper and lower arm pivot holes
3.2mm for all screw holes excluding the lower arm
3mm for the two lower arm screw holes

Use caution when installing the lower arm on the swivel post! The post is narrow, and will break easily. Be sure to deburr the post and check for roundness. The post is quite strong once the screw is installed. If the post does break off, it is still completely usable as long as it is complete and located in place when assembled. The post merely acts as a standoff.

One binder clip arm is often enough to provide more than adequate tension. There are four spring slots available for your super filament crushing desires, but beware, too much pressure can cause premature failure of the swingarm, and deformed filament.

The alternate lower arm is designed to work with an M4 nut threaded directly on the bowden tube, whereas the standard lower arm uses the 4mm push to connect fitting. Take your pick!

The 608 size bearing is a standard that fits in most scooters, skateboards, rollerskates, fidget spinners, etc... You can find them everywhere!

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i have problems extruding i have to clip arms in the middle, i am underextruding i dont know what to do

Binder clip arms as springs, brilliant!

Hi, love the design and have one on my Kossel Mini. Might I suggest building out the arm so that flexible filament has less chance of buckling? See http://recreus.com/en/content/11-learn.

Not a bad idea, I'll look at what is possible when I get some free time.

Hi, I would like to make some mods to this design. Would you mind sharing the CAD file, STEP file format would be great so I can import import into PTC Creo or Autodesk Fusion 360?


Hi, Don't worry about my request for CAD files, I used FreeCAD to import them and covert them to STEP. It's few step process and not perfect but it works well enough.


Both would work perfectly. I would probably order the one on ebay, I like that style a little more.

As long as it's 4mm, you're good.

Sorry if it's a stupid question, how do you attach this to the 3D printer? I can't find any pictures that show how it's attached. I have prusa i3 rework btw :)

It attaches directly to an aluminum extrusion - OpenBeam or similar - on your printer via the upper two M-25 screws at the top of the first two included photos.

Very cool design!!!! Thank you!

Would it be possible to get a version with the entry guide hole for the filament (from the spool) extruded out another 5-10mm or so, maybe to the edge of the base? I've had that part snap off two times now in trying to remove filament.

Let me know. Thanks!

I have already made the update which includes the modification you describe, but it's only complete for the MK8 drive gear. I can upload those files today, but the MK7 version will only be available when I have time to make the changes.

Made the updates to the MK7 as well and uploaded all the new files. Enjoy!

You're my hero! This extruder has made all the different to my Kossel Clear. I'm printing R2 right now, I'll post a picture when I'm done.

i have cnc machined one --- it is killer thanks so much !!!! here is a little vid !!


Looks fantastic!!!

Would you mind uploading source files for this? I'd like to modify the design a bit to make it fit the mounting pattern for a NEMA17 with a planetary gearbox as well as modify it for the 1/8 BSP connectors that come with e3d hotends.

Anyone know if this will work alright with the mk8 drive gear?

As stated in the "Thing Info" tab, "The MK7 and MK8 versions are each designed to work best for those particular drive gears, or gears with similar dimensions."
So, yes. Just make sure you print the MK8 version.

2 questions
Can we have the original model for change in relation to need.
Otherwise you have quotes of objects (size of holes, distance piece Free ....)
Thank you for your sharing.

I really like your extruder but i'm having a problem printing it out, the little loop that the filament goes through is a little fragile, is there any way you could beef up that section?

Love the design. I have been looking for an easy to load bowden extruder for a while and this looks great. Nice work!

very neat that you used commonly available binder clip handles as the spring. I have tons of the 2 cm clips that come in handy for all sorts of things. way to innovate.