Ultimaker 2 Straight tube flexible filament spool holder

Ultimaker 2 Straight tube flexible filament spool holder

3D printer parts and enhancements

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With this little tower you will straighten and make shorter the bowden tube. This will highly improve print quality of flexible materials (see attached photo of Semiflex filament).

Note that you will have to print Hinge.stl and FlexConnector.stl from flexible material. It still works like a charm (and did not break in the months I used it), so it is time to share. Models of my CAD program (ZW3D) are included in the 7-Zip file.

Achieved results: Printing NinjaFlex and Semiflex in layers of 0.1mm thickness without problems. Printspeed as with normal materials. Retraction still did not work.

Some ideas behind the design:
- Makes it possible to print flexible materials, but still with a lightweight printhead (allowing fast movement)
- The springs on the back will lift the heavy extruder-motor, and act more or less as a kind of gravity compensation.
- As the tower is part of the printer, it keeps the printer relative portable
- Spool holder is oriented such that the filament bends in the direction how it goes through the tube, instead of making a 90deg twist like in the original setup. This prevents additional stresses to build up in the tube/guide.
- When mirrored, two towers can be mounted; dual head compatible.
- Spool holder shaft can be easily taken out of the tower (complete with spool, bearings and 'Spool Holder Centerring'), this makes it possible to easily exchange spool from front of the machine, even when two spools are mounted.
- Filament spool holder has been improved (using bearings for smooth roll-off, using bearings to guide the filament into the extruder)
- Any extruder should work, you can use IRobertI's Alternative feeder V2 (https://www.youmagine.com/designs/alternative-um2-feeder-version-two).
Note 1: you should break the guidance for the filament, because the axis of the motor and the small bearings that guide the filament in the extruder will conflict with it. See photo "Extruder.png".
Note 2: You should also add the small modification in order to be able to print flexible material. You can find it here: https://www.youmagine.com/designs/feeder-bearing-mod-for-flexible-filament
- Note 3: As the extruder is still about 20cm away from the nozzle, retraction still does not work (as far as I have tested).
- Note 4: As I am a little lazy, till now I did not try to align the feeder parameters. I just manually insert the filament, and then set manually the material type by selecting it via the settings in the ultimaker display menus. Don't know if we can tweak the auto-feeder distance, I would expect a parameter in the machine parameters of Cura.

Making a video while inserting material with my other hand was a little difficult, but here it is:

Materials and methods

- Printed parts (as shown in STL files)
- 4x RS 821-396 spring (http://nl.rs-online.com/web/p/extension-springs/0821396)
- 2x RS ball bearing 619-0288 (http://nl.rs-online.com/web/p/ball-bearings/6190288/?searchTerm=619-0288)
- 3x RS ball bearing 893-7420 (http://nl.rs-online.com/web/p/ball-bearings/8937420/?searchTerm=893-7420) (-> Note: these bearings might not be required! I have been printing for a while now without and that seems to work better than with bearings, as sometimes the filament gets stuck in the gap between bearings.)
- Some M3 bolts & nuts (note that you can re-use the bolts of the existing extruder for fixation of the tower to the printer, for mounting the extruder and springs you will need new bolts)
- Some wire&shrink sleeves to extend the wire of the extruder motor



Issues are used to track todos, bugs or requests. To get started, you could create an issue.


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5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg commented ago

Hi Norphi, these bearings are used to make filament roll-off smooth. You should mount them bweteen the 'spool holder shaft' and the 'spool holder centerring'.

973dcd3e790afb307d7a3b2ccb7bd7ec?default=blank&size=40Norphi commented ago

Hi Antonverburg!

Thanks for your efforts to make FlexFilament printable. I've struggled a lot with that stuff!

I'm approaching assembly of the tower but I can't quite figure out what the two 619-0288 bearings are for. Little help?



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53f0ad2f129c1af1749fb14f8d310b64?default=blank&size=40Rich Tech commented ago

Hello Antonverburg

Thank you for uploading the hinge file.

I did print all parts and assemble the unit.

I have had great results. I was able to print with Ultimaker White flex PLA at standard (default speed). The print was over eight hours and I had no problems at all. I found that I could run at 195 deg. c and 40% flow rate. The speed rate was the same that I used to print with standard Ultimaker PLA. I ran a second test part which is a mud tire for a scale model. It is 1.8 inches dia.

I ran it 100% fill and again at 195 deg. c but at 75% speed.

One thing I did was to move the Bowden tube right up to the bearing and the knurled driver.

By doing this, I had no buckling of material at all.

Great Idea thanks for sharing.

Rich Tech

5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg commented ago

Another issue: it seems that the three bearings on top to guide the filament are not required. On my own system I have actually removed them because as the filament could slip in between two of the bearings, sometimes the filament stuck there instead of being guided. Using Roberts V2 extruder the metal ring already does a good job. I will keep you updated, and if I really leave them off finally update the models with this modification.

5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg commented ago

It is correct that hinge was missing. I have added it.

About de differences between video and design: during assembly I saw that I had to break away some parts to make it work smooth, and also some other details broke directly without use because they where too weak. I have changed the models accordingly, but I did not print the new models for myself. That's the reason of the differences. Models should fit, if not let me know, so that I can modify them for you.

53f0ad2f129c1af1749fb14f8d310b64?default=blank&size=40Rich Tech commented ago

Hello again

I notice that the spool holder centering file is different from the video.

Is it possible that The files here are not the current ones.

Thanks again

Rich Tech

53f0ad2f129c1af1749fb14f8d310b64?default=blank&size=40Rich Tech commented ago


I have printed all of the parts and have begun assembly. Looks good so far but I don't seem to have the "Hinge file." I don't see it here on line?


Rich Tech

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5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg commented ago

Added a little video of loading material & startup of a print job.

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Mini profileChristopher Bray commented ago

I would love to see a video of this in operation!

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5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg commented ago

I just replaced the files with files that already have the correct print orientation.

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5aed33055598060b78c7c1d277253e86?default=blank&size=40antonverburg published this design ago