About This File
This is a very simple modification to the Main Body of the Stealthburner Clockwork 2, to improve performance when printing TPU.
I found that when printing TPU, particularly the softer Shore hardnesses, the extruder would frequently skip, stutter and misbehave, causing poor quality prints. After studying the CAD files, I reasoned that as the direct drive outputs the filament into a bore in the Main Body, before the PTFE tube, the filament might be compressing at this point, and jamming up in the higher friction printed plastic.
To remove this issue, I continued the 4.2mm bore for the PTFE tube all the way up into the direct drive chamber. This allows the PTFE tube to be extended, and carefully cut (with a scalpel, or craft knife), to exactly match the direct drive gear. With this change, the filament outputs from the direct drive gear directly into the PTFE tube, with no opportunity to touch the higher friction printed plastic, and no space to jam up in.
I have found that this simple modification dramatically improves performance with printing TPU on my printer. Hopefully it'll do the same for you.
Note that getting the length of the PTFE tube exactly right with this arrangement is a little bit tricky. Cut the tube too short, and you'll be left with a gap that the TPU can compress into (giving you the same problem), but too long will cause it to foul/drag on the direct drive gear. Easiest thing to do is to sort this out first, before you build the rest of the Clockwork.
Fit a length of PTFE tube to the Toolhead & holder of your choice, and cut it so that ~25mm is extending from the top. Slot this into the CW Main Body, and the tube should end approximately half way across the direct drive gear chamber. You can then use the sharp scalpel/craft knife to follow the contour of the chamber, as shown in the photograph attached.
Hope this is helpful!