I’ve just noticed that the tensioning screw no longer works on my extruder head. That is, if it’s dialed all the way back (untensioned), it slips. I can get it to start if I dig my thumbnail in behind the nut, but it won’t work for very long …
Is this a common failure? Not sure what I’d have to replace. Seriously considering buying a new head at this point - I’ve torn it down completely some 20-30 times in the last year or so.
What toolhead? SE 0.5mm is common on the Mini 2, but it supports half a dozen toolheads, and some tension very differently.
Assuming it is the most common SE 0.5mm, I would guess that the tensioning isn’t working due to a bad spring, or it’s been broken during one of the 20-30 times you’ve torn it down.
Also, that’s a lot of tearing down, so I kinda have to assume that you’ve been doing something wrong this whole time to necessitate continually taking it apart, or you love changing nozzle sizes and are a glutton for punishment.
Some detailed pictures of your tensioning on the toolhead would help the most, and if you don’t mind taking it apart a 21-31th time this year, shots of the internals might help with seeing if something is broken.
It’s the standard 0.5 mm head that comes with the mini 2 - or did three years ago, anyway.
Many times I tore it down because the filament kept getting stuck in the plastic tube. So, I did the tear down / warm it up in the oven routine many times before I realized my fan was dying. Not long after that, the other fan died.
Overall, though, the worst I’ve done that I can see is strip out the threading for one of the screws in the heatsink.
Apart from that, maybe the threading on the tension screw or nut got damaged? Not sure, but it looks ok to me.
Anyway, attached are the pictures. And for however many times I’ve done this, the grounding wire crimp ring broken finally broke off this time just so I could get these shots. 
Everything here pictured looks ok, but the tensioning screw, spring and nut aren’t present, and would be one of the more likely things to be the cause of failure.
That’s because I took them out to get a separate shot of them. Apparently, the forum software didn’t like it.
Yeah, these threads are stripped:
Should look like this:
Cheap to replace though: E3D Titan Thumbscrew - 3DJake International
Be sure to replace the little M4 nut too.
Thanks! I appreciate it.
