Printable push to fit bowden nut-couplings

by Erik, published

Printable push to fit bowden nut-couplings by Erik Aug 12, 2010
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More details on the Bowden extruder system: http://reprap.org/wiki/Erik%27s_Bowden_Extruder

I just made a serendipitous discovery:
I printed a very narrowly fitting freely rotating coupling and it had such a good grip on the PTFE that I printed another with just a little more contact area. You don't need the nut anymore for the Bowden cable!
I had been looking for push to fit couplings ever since Charles Pax showed me how good they fit to 1/8" PTFE cables. Now it appears that they are definitely printable!

The current push to fit coupling can be removed sideways. If you pull it sideways at the top first, you can pull it out with the plastic filament inside. It's a huge benefit to not have to pull back the plastic first.

A variant with a clip that you can pinch with your fingers would perhaps be even better, but this one is so simple and very functional and it hardly takes up any space.

I also included a cable to cable coupling, you just put in two cables sideways.

When done correctly, this type of friction from printed parts could be used for the extruder drive mechanism too, replacing the metal pinch-wheels that we currently use. In any case it can already withstand more than the force the force that the filament is driven with, and that's with ultra-slippery PTFE!

It would also allow us to print fasteners! Though perhaps a simple plug and a cam mechanism will better do the trick. And if you get a similar friction fit on the filament itself, you can start ysing that as structural material too (with some creep, but you could re-tension things once in a while).

Which other non-printed parts can we eliminate by a superior (I'd like to think this is an improved part, but only time will tell) printed alternative?


The Darwin one has its 5 mm bolt holes 33.5 mm apart.
The Mini-Mendel one has the 60mm apart, and should fit an M3 bolt.
The hose-to-hose coupling is to connect two pieces of PTFE bowden cable.

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Printable push to fit bowden nut-couplings by Erik is licensed under the GNU - GPL license.

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Are those for 1/8" inner-diameter or 1/8" outer-diameter tubing?

Where do I find the cold end for this type of extruder? The part with the hobbed bolt, motor, etc.

While testing this out, I accidentally printed one too loose in PLA, and found that wrapping a bit of blue tape around the PTFE makes it stick really well.

Sorry. I added the part to the parts list!

What kind of PTFE tubing are you using and where did you source it?


(click on the part in the list to find the supplier(s), currently only one in the UK.

Where is the parts list?

Hello Greg,
The parts list is removed by Makerbot since that functionality wasn't seen as part of their plan. I believe that parts lists (or Bill of Materials, in short BoM) are important to replicating more complex projects and very desirable for open source collaboration. On YouMagine, a website that we're developing, you're able to host designs including a BoM. You'll find that it's very community friendly and pro-open source collaboration.