How often do Bowden couplings need replacing

[TommyDee]

I love this subject as it is rarely considered and only a moot issue for many.However, I run replacement tubing on a system that wasn't intended to use them.Furthermore, this system requires the extruders (2) to be installed using a 135 degree rotation.

And on the spool side is a cartridge bulkhead that come off the printer and of course, the bowden tube comes along as an umbilical cord.So here's the real deal with all push-to-connect fittings; the grippers are sharp; they grip a sharp edge into the material; they rarely rotate freely; and they leave a nasty groove in the bowden tube if you twist the tube in the fitting. This is when the tube gets stuck.... and this is when the fitting grippers break due to lack of options - you yank on it.

Again, umbilical rotates on cartridges when changing cartridges; fail!
Remove extruder by ccw twist of 135 degrees and ; fail!

No matter how hard you try, this failure mode was plaguing me on my Cube3's. I went through nearly 2 dozen when I said enough! Bowden tubes were getting shorter and shorter. I needed a solution.

I came up with one but that's not the point of the comments; the point is, as Aardvark pointed out, good and bad fittings. The failure mode described here is only to say that PTFE tubes in Push-to-Connect fittings are not sanctioned by the fitting manufacturers (OEM's based on design criteria, not copy cats wanting to sell product) and do cause this possibility of getting 'stuck' in the fitting if the tube is rotated. Not an immediate failure mode, but in short order it will wear a groove deep enough to catch the grippers.