Would anyone happen to know if there’s a specific brand/type of 4mm OD bowden tube that is the most flexible? The generic transparent bowden tubes are not as flexible as we need them to be. Any tips appreciated!
Well there’s always McMaster 
Only referring to 4mm OD. We currently use 3mm OD tube and it’s really flexible, but we’re switching to John Guest’s embedded fittings and they don’t make them for 3mm tube (even though they advertise they do), only 4mm tube. So now we have to search for a flexible 4mm tube. Need to know a company that makes a really flexible 4mm tube or at least the type of material that would make it flexible.
For example, I noticed that the semi-transparent tubes tend to be more flexible than the fully transparent tubes. Or maybe it’s the same? What material are the semi-transparent tubes?
Have you tried PFA or FEP? Both are fluoropolymers that are more transparent than PTFE and available in tube form.
@Whosa_whatsis I have not, first time hearing of FEP. Are they more flexible? Do you know any good suppliers?
Our issue (and reason we went with 3mm OD tube) is that the 4mm OD tube is not flexible enough. And because our Delta Go is small, whenever the hotend got too close to the extruder, the tube would be forced to bend a lot and that causes a lot of compressed pressure on the tube, causing it to want to push the hotend away from the extruder. If that makes sense.
Sounds like your tube is too short.
Not sure about FEP, it might be a little stiffer. I think what I’m using now is PFA, and I prefer it over PTFE.
PFA is usually a little more expensive than PTFE, looks like FEP is cheaper. For my own purposes, the short lengths on Amazon are sufficient.
@Whosa_whatsis McMaster has PFA rated at 38mm bend radius whereas FEP is 15mm and 38mm bend radius.
And yeah for the 4mm tube we’re testing right now, it is a bit short. Need to add probably 25-50mm, otherwise the bend force is pretty strong when the hotend is homed to the top.
FEP coefficient of friction is substantially higher than PTFE which will degrade performance in Bowden systems - flex filaments most particularly.