CR-10 flexible filament extruder bracket with adjustable spring tension

thingiverse

**Intro:** I was exploring the usefulness of oiling the filament when I found that the extruder was slipping on the filament because it was so smooth (after oiling). I realised that in the current design of the extruder, there is no way to tune the tension of the extruder gear on the filament. After searching the internet, I was surprised that I could not find any other readily available design for our stock extruder to adjust the spring tension, hence I designed this to allow for the spring tension to be adjusted. Video of how the tension can be adjusted can be found here: https://youtu.be/szChddRyo70 Note that my design would end up sacrificing one of the mounting holes. **Note:** I recommend printing this in a material with better heat resistance than PLA (I reprinted in PETG) as mine warped from the heat from the extruder motor below it, resulting in a crooked filament path. **Parts list:** - 1 x M5 30mm bolt (a shorter bolt would make installation difficult) - 1 x M5 washer - 3 x M5 nut **Assembly:** - print out the bracket (duh!) - insert one of the nuts into the hole. It is friction fitted into the slot. Make sure it goes completely in (see pic). I found it easiest to screw the nut onto a bolt and use the bolt to guide the nut in. - screw in the M5 bolt almost all the way and insert the other 2 nuts. There should be a small part of the bolt exposed (2-3mm) to ensure a good hold on the spring when it is installed (see pic). - using 2 wrenches, tighten the 2 nuts against each other so that they are locked in place - when the bolt is unscrewed all the way, the nut should be more or less flush with the surface (see pic). This would be equivalent to the stock tension. - insert the PTFE tube with the appropriate cuts for extruding flexible filament - install the bracket onto the z-axis bracket with the extruder arm - insert the M5 washer against the stock arm where the spring goes (without this, the spring will turn against the plastic part when you tighten the tension which may strip the plastic, see pic). - install the spring and the bowden tube and you are done!! (see pic) Do note that in terms of dimensional tolerance, I used the CAD file provided by SizZLeR to jump start the design but most of the holes were too small for me (the dimensions by joshvv was perfect for me). Hence in the .stl that is provided, they are sized back up to fit my tolerances. In the included Fusion 360 file, you will find many sketches inside that are used specifically just to enlarge the holes. Use that to adjust whatever hole size that you need to meet your needs. I would really love to hear your comments on the design and what you think about it, thanks! **Update:** *29 Oct 17* I have included a new version for those who are using the extended arm. I found that the screw's position makes it difficult to release the filament. In the extended version, I took the opportunity to also include a cable bracket. *30 Oct 17* I have redrawn the extire extended arm from scratch in order to match the bracket that have designed. The original arm design that I have was a little loose and caused the roller to shift off-axis resulting in the filament getting jammed. The new version 3 of both the stl files are meant to be used as a pair. I have also used the opportunity to design a filament guide into the arm which requires a PTFE tube to be insert to guide the filament in smoothly. *2 Nov 17* Due to some of the minor tolerance issues,I completely redrew from scratch the entire set of bracket and arms and modelled them parametrically so that the alignment of the filament guides would be perfect (at least parametrically). After more than 10 iterations, I believe this is the ultimate in terms of accuracy for the filament guide. Hence I have deleted all previous version and only left behind one version. In this new version, there is also no longer a need for a PTFE tube for the roller portion. You would only need 1 piece (around 5cm long) for the feed from the outside into the rollers. *3 Nov 17* The screw holding the idler gets bent over time if the tension is tuned too high. Hence I designed a version 2 that holds the screw in both the top and bottom position such that it is secured and unlikely to get bent over time. This however requires support to print (and is quite a pain to remove). I included a pic of the new design on how it looks.