When it comes to printing we all know why we use teflon tubes to guide our filament.
But not too many know why we won’t use Polyurethane, PU tubes…
Both claim to offer a high chemical and abrasion resistance combined with low friction features.
If you ever tried PU tubes though you quickly went back to PTFE once you realised how damn noisy they can be.
Won’t take long at all and all you hear is terrible squeaking.
In my jobs I learned that one can abuse almost anything if it fits the purpose…
And we abused PU hoses and tubes a lot, not just to get air and liquids through them…
After printing some TPU gears and sleeve bearings I noticed that printed PU does not really make much noise at all…
But also that, at least for low load conditions, they make great replacements for metal parts.
So what’s the problem with those PU tubes then ?
Only one way to find out - putting some into the P1…
Glow filament is really bad, so I tried it with the PU tube in order to find out what the issues might be…
None, no noise, no failures, no transport struggles…
Whiskey Tango Foxtrot ??!!
And by hand the PU tube let me feed the filament much easier as well…
So it seems all those years back someone managed to pull a great hoax and ever since everyone avoids PU tubes for no reason…
What about normal filaments then…
There we go - like nails on a chalk board LOL
PETG wasn’t too bad though…
CF anyone ? No noise and easy to push…
What could possibly cause such a big difference and make those filaments that eat our costly PTFE tubes go through PU so nicely ?
It’s the surface 
The glow filament is like coated sandpaper, the CF filament finer but similar and even TPU runs through PU tubes better is the surface of the filament is textured.
The noises are the result of two very smooth surfaces rubbing and both are surprisingly resilient on their surface…
If you print filled filaments a lot and they keep eating up you teflon tubes try some cheap PU tubes to see if in your case they outperform the teflon as well.
If, for whatever reason, you want to try PU tubes with normal filaments and find it too noisy:
Run some 000 steel wool through the tube.
Pulling with a good string works best but if you won’t use too much pushing can work as well.
You don’t really want to sand the inner surface, just dull it a little bit so the shine is gone.