Using a Bowden cable on the reprap prusa cold end


This post is to document something that I thought was fairly standard , but after talking to a few people I discovered it isn’t. Some people (I’m looking at you jkeegan) even thought it wasn’t possible. I have been using thin hdpe tubing for some time to enable my extruder to unspool filament by itself.

The benefit of the tubing is that it removes the effect that pulling has on the carriage positioning. The cable has a small washer between it and the extruder, and butts against a 3mm hole I drilled in the handle of my extension cord reel. That arrangement allows all of the pulling force of the extruder to be focused on spinning the reel as opposed to lifting the z axis off of the bed.

I used this setup most of the time I was working with the cupcake, and just set it up again for my gen 6 prusa.

Downsides: it does probably require more torque. You also need to be smart about using as little hdpe tubing as possible, as it seems like the friction scales non linearly. You also want the line to be as straight as possible between the spool and the extruder. My setup in the video is about as long as you want it to be. I could easily see using 10cm of tubing and simply setting the spool on the top of my prusa. That ought to have very little drag compared to the current rig. PTFE tubing might be worth looking into as well

I may end up building a bracket to allow mounting the reel on top. That seems like it would be a pretty manageable setup.

Just because I know someone will end up asking where I got that reel from: home depot is the answer, but you can also find it at amazon here

The hdpe tubing I believe is used for cold water lines such as ice makers. I picked it up at home depot as well.

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