Hot End PTFE Tube issues
How often do you need to adjust your hot end because of the PTFE tube? I have to do it almost every three days because [I'm guessing] it shrunk. I thought after 1-2 times it would stop shrinking but that doesn't seem to be the case. I have had many very long prints fail because of it (causes the Bondtech extruder to start clicking). It's over 2mm shorter than it was when it was new.
RE: Hot End PTFE Tube issues
I have Bondtech heatbreak for several months now and I never had this problem so far -that is, there was no need to take hotend apart during that time.
But the way you described that (and you're not the only one having that problem), it made me thinking how this could be solved with stock heatbreak. I'll try to explain...
Yes, PTFE tube shrinks inside heatbreak because of high temperature. After tube becomes shorter, we get a gap on both ends and filament will start to deposit at the bottom side (where temperature is getting close to melting point). And sooner or later, that deposit will manifest itself as clog.
What is important in this case, is the fact, that PTFE tube doesn't shrink endlessly. I assume, it will shrink mostly during first few heat-ups. After that, PTFE tube won't shrink substantially anymore -it will keep it's length.
What I would do is... Cut new PTFE tube 2mm longer than recommended length. That is, instead of 43.4mm, make it 45mm long (don't forget chamfer on both sides). Now, make sure that heatbreak is clean inside, assembly the hotend and secure those 3 grub screws while pushing hotend upwards. Yes, I know, nothing new so far... here it comes:
Now, without inserting filament, set nozzle temperature to 260°C (in case you print PLA and PETG) and leave it at this temperature for about (I'm guessing now) 15 minutes and then cool down the nozzle. By making a pause inbetween (so hotend fully cools down), repeat this process few times (let's say, 5-times).
After you did all that, PTFE tube has shrunk to it's final length, and won't shrink anymore (so my theory). Finally, you loose those three grub screws, push hotend upwards and secure grub screws again.
That's it. Now I'm really curious if my thinking is correct.. 😏
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