Nozzle comes loose
I have two Prusa MKS3+ and have the same problem with both, the replacement hardened steel nozzle keeps oming lose in the hot end.
I have a torque wrench (purchased, not made) that is supposed to do 2.5NM. It certainly feels tight as use it, but I am finding over a few weeks the nozzle gently becomes slighty loose. I can always tighten it further after a few weeks.
Is this normal at all? I'm only printing PETG at the moment.
Its a bit of a pain as I keep needing to readjust the Z level.
Any suggestions welcomed.
Thanks
Rob
RE: Nozzle comes loose
Do you tighten the nozzle when it is hot? Also there are different metals (hotend, nozzle) involved that have different thermal expansion behaviour. This can cause the nozzle to come loose over time.
RE: Nozzle comes loose
Walter,
Thanks for this. I unscrew the fan, and the shroud and heat the end to 280C, I put a adjustable spanner on the hot end that just fits and doesn't cramp the wires and tighten the nozzle using a T-handledTorque wrench to 2.5NM.
The nozzle is a hardened steel nozzle as opposed to a brass one.
If this is normal behaviour and every 2-3 weeks I need to do it and everybody else does it, thats fine.I don;t have anybody to ask where I live and both Prusa's are the same.
Am I the only one?
Thanks
Rob
If you search you will find several threads here in a similar vein. Some combinations of nozzle and heatblock material with very different thermal expansion coefficients are particularly susceptible.
Cheerio,
RE:
Yes, given the different combinations of materials used in nozzles, heaterblocks and heatbreaks, it’s really a case per case scenario. Best solution IMHO would be to get all these parts made from the same metal. For instance, nickel plated copper for nozzle and heaterblock and the bottom of the heatbreak made from copper too.
This way there’re no different thermal expansion coefficients to consider and a low(ish) torque of 1 Nm, or even less, would be enough to keep everything nicely tightened, no matter how much you heat up the hotend. You could do cold nozzle changes as well, provided there’s no solidified filament connecting the inside of the nozzle and the bottom of the heatbreak ( a cold pull would take care of that ).
Of course, if you want to use a hardened steel nozzle for abrasive filaments it’s a different story but, in that case, you might use instead a copper nozzle with hard tip insert ( ruby, TC, diamond..)