Ender 3 with direct drive has severe stringing printing TPU I recently upgraded my Ender 3 Pro with a direct drive kit, primarily so I can print soft materials like TPU. I bought a spool of Overture TPU to try it out.
I'm getting really bad stringing on every print, to the point where it's pretty much unusable. This is my first time printing with TPU, so I'm at a loss for what to do.
Direct Drive mod -
After modding the printer I did a few prints with PLA, and it works great with very little stringing. So I assume I assembled the mod correctly and that's not the issue.
Material -
Reviews of the Overture TPU on Amazon mostly say it has low stringing and are generally positive, so I'm assuming it's not just bad filament.
Temperature - The consensus in the Amazon reviews seems to be that 230°C is the sweet spot. I did a temperature tower from 205 °C to 230 °C by 5 °C, and the print quality and stringing was pretty much uniform throughout.
Retraction - I tried with retraction off, then with 1 mm, 2 mm, and 6.5 mm, in various combinations with temperature and speed. Results varied in details, but all were pretty bad.
Speed - I tried slowing down to 15 mm/s (from Cura's default of 50). Results got even worse.
Following are photos of a stringing test with various combinations of settings.

PLA for reference - 205 °C - Layer thickness 0.2 mm - Retraction 1 mm

TPU - 205 °C - Layer thickness 0.2 mm - Retraction 2 mm - Print speed 15 mm/s

TPU - 230 °C - Layer thickness 0.2 mm - Retraction 1 mm - Print speed 15 mm/s

TPU - 230 °C - Layer thickness 0.2 mm - Retraction 1 mm

TPU - 230 °C - Layer thickness 0.2 mm - Retraction 2 mm

TPU - 230 °C - Layer thickness 0.2 mm - Retraction 6.5 mm

TPU - 230 °C - Layer thickness 0.12 mm - No retraction

TPU - 240 °C - Layer thickness 0.2 mm - No retraction
Is there something else I should try to reduce stringing? Is it possible that I just got a bad spool of TPU? Or is it more likely something's wrong with my printer?
Due to the flexible characteristics of TPU, stringing is a known &quot;complication&quot; with this material.

                
             is a video from Matterhackers:

no retraction - stringing is expected
dry filament - ensure the filament hasn't been exposed to the air for extended periods - use an oven or dehydrator if needed

There are many other tutorials and videos covering the process.
Tom Sanladerer has also a video covering the use of flexible filament.

ensure correct alignment of hobbed bolt and feed hole
consider to use a piece of PTFE tubing downstream of drive mechanism
use 3 mm (usually 2.85 mm nowadays) filament for better results (if possible)
bed temp - 40 °C with glue stick on bed
print slower
adjust extrusion multiplier by testing various settings

Obviously some of the above references don't apply or are being observed.