Beware of HF Nozzle Creeping Out of Hot-End!
The availability of new High-flow nozzles is great for improving printing speeds. However, I have discovered something I did not expect: The increased force exerted on the nozzle by the extruder is enough to cause it to creep out of the hot-end. I tightened the thumbscrews as much as I dare, as I am concerned about damaging the nozzle tube. This is something to keep an eye on.
Obviously this will lead to print quality issues (z-axis errors), as well as bed leveling and nozzle cleaning problems. If the nozzle gets pushed out too far, the filament can jam at the top of the nozzle. It would be nice if there was a groove in the nozzle tube where the lower thumb screw engages to prevent the nozzle from creeping downward.
RE: Beware of HF Nozzle Creeping Out of Hot-End!
Can you explain more what you mean? There are two grooves in the nozzle, each about 3mm wide and roughly 23mm apart, matching the distance between the thumbscrews (the camera angle isn't perfectly square, but it's close):
The nozzle is threaded into the heater block. If it's properly tightened ("The specified torque value is 1.5 Nm (13.3 lb-in). The use of a torque wrench is recommended"), it seems very unlikely to push out from the block.
If you mean that the entire hot-end assembly is sliding down out of the heat sink (including the heater block), make sure that (with the thumbscrews loosened) you have pushed the nozzle far enough up that the copper ring on the nozzle is not visible. (That picture somewhat awkwardly shows the copper ring; a pair of pictures with this one as what not to do and another showing it fully inserted would be better). On my printer, as I get the nozzle in all the way there's actually a little "pop" as the top of the nozzle pushes into the filament guide hole in the Nextruder's main plate.
RE: Beware of HF Nozzle Creeping Out of Hot-End!
Thank you for responding David. I am not certain why it happened to me. Both thumbscrews were tight, but I found that the nozzle had slipped about 3-4mm out of the hot end. I had to loosen the thumbscrews to push the nozzle back up. Perhaps I had not inserted the nozzle far enough in the first place?? I cannot rule out this likely possibility.
I did a quick test, and found that I could loosen the thumbscrews 1/2 turn and the nozzle would not slip down. I could feel where the thumbscrews engaged the grooves. In the future I will verify this engagement when I install nozzles. A light tug on the heater block with the thumbscrews slightly loose will confirm whether the nozzle is inserted all the way.
Regarding use of a torque wrench per the instructions, this is not feasible with thumb screws.
RE: Beware of HF Nozzle Creeping Out of Hot-End!
Regarding use of a torque wrench per the instructions, this is not feasible with thumb screws.
Indeed not; perhaps I could have been more clear. That linked text is to the instructions for tightening a nozzle into the heater block, not for tightening the entire hot-end assembly to the heat sink. I don't recall ever seeing anything more specific than "do not overtighten" for the thumbscrews.
RE: Beware of HF Nozzle Creeping Out of Hot-End!
On re-reading your messages, I think part of my misunderstanding what you meant is that you -- and Prusa sometimes -- are using "nozzle" as a shorthand to refer to the combined assembly of nozzle + heater block + silicone sock + heater + thermistor -- those parts which together slide up and down when the thumbscrews on the heat sink are loose. I generally -- and Prusa sometimes -- refer to that assembly as the "hotend" which is part of the extruder, e.g., https://www.prusa3d.com/product/nextruder-hotend-brass-0-60-mm/ I'm still used to the V6 era where the "nozzle" is just the conical bit of brass that you see at the bottom 🙂 E.g., https://www.prusa3d.com/product/nozzle-v6-0-4-mm/ Where you wrote "nozzle creeping out of hot-end" I should have understood you to mean "hotend creeping out of heatsink" (or out of extruder) as I use the terms. Not at all trying to criticize, just clarify... terminology keeps changing along with the technology!
RE: Beware of HF Nozzle Creeping Out of Hot-End!
You are correct David. I am referring to the assembly that is held in place by the thumbscrews. I apologize for using incorrect terminology. I should have looked it up!!
Your pointing out that the grooves mate up with the thumbscrews made me aware, and I will adjust my procedure when changing nozzles.