I’ll preface this that I don’t have experience with TPU, but I have successfully printed PLA, ABS, HIPS, PETG and nylon, as well as specialty filaments from Taulman, 3DXtech and Polymaker.
To avoid stringing, dial in your retraction settings. Here is a good retraction test print:
Start printing with your default settings. If you get stringing, increase your Retraction Distance (under Material in Cura 2). Typical settings are between 0.5 mm and 1.0 mm, but might be a bit higher with TPU (guessing it is a bit gooey like PETG). Don’t increase your Retraction Distance too far, then you can get blobbing when the extruder re-pressurizes the nozzle as it starts the next section of print. The “Goldilocks” setting for most materials is the distance just far enough that it stops stringing so that you can maximize your print speed. Also check your Retraction Speed, for higher quality I have it between 5 and 10 mm/s (also because the Cura default PLA setting of 24 mm/s was grinding my filament).
As kcchen said, slow down (although going too slow can cause problems too). Ringing is caused by the belts having to stop and start the mass of the toolhead. Since the effect is on the outside of the print, the critical setting is Outer Wall Speed (under Speed in Cura 2). You can try 10 mm/s or perhaps as slow as 5 mm/s. Here’s a ringing test print (I haven’t tried it myself however):
Fan settings will also affect print quality: More fan for better part accuracy, less for stronger parts and it’s strongly dependent on material (PLA loves fans, ABS hates them). Again, I’m not sure how TPU will behave, gotta find that “Goldilocks” zone. In theory, the Aerostruder will make for more uniform parts because of the fan shroud, I notice that one side of my prints turns out better than the other on my 'Mini because the Hexagon toolhead only has one directional fan.
You might consider the new water-soluble PVA support materials such as PolyDissolve S1 over HIPS. Water seems easier to use and the results seem better than Limonene (watching co-workers do some dual-prints with soluble support, not sure if TPU plays better with HIPS or PVA):
We haven’t had the best of luck printing with the Dual V3 yet, but haven’t spent the time hashing out the processes either. It might be that Simplify3D is better than Cura 2 for processing dual prints. The general consensus is to avoid the headaches of dual printing if at all possible and use breakaway support, but it might not be practical with TPU.
It’s all process development as you try to get the most out of your machine and filament. Having a collection of good test prints will help you characterize your process and make the best quality prints (or trade-off quality for speed, etc.) Good luck, and please post pictures of your results on the forum!