RockLobster 2017-11-17 20:03 edit
Set a job running this morning, waited for it to print the raft which went just fine, came back to this mess.
This is onlt the 5th job Ive run, been imensly happy until now, but I honestly don't know how to proceed, the extruder assembily is fucked AFAIC, do I try and peel it off and print spares or is it a gonner?
Thanks for this mate, I'll try and rescue it tommorow and see how I get on.
Coop I owe you a pint.
4 hours later I'm finally back up and running, and it's busy printing a full set of replacement parts (printing a fan duct without a fan duct is harder than it sounds)
It's aircrash investigation time, so I'm going to give you the narrative of what I think happened, and then my rational afterwards.
At some point during the first few minutes of printing the PEEK nozzle cover came lose and dropped into contact with the bed / part being printed. As the nozzel was still very close to the bed the PEEK cover was trapped and began rubbing, first on the printed part, causing it to become detached from the bed, then on the bed itself. Whilst this was happening the machine continued to extrued plastic, causing the PEEK cover to remain in contact with the bed as it was continously being forced forward on a coloumn of semi-molten plastic, and eventually resulting in the rather messy result pictured above.
Rational as follows.
Whilst removing the plastic build-up, the nozzle cover had clearly been "extruded" on it's own narrower column of plastic, which had then become embeded within the larger mass.
Something non-metalic has been rubbed extensivly on the bed, persumably not molten at the time of doing so.
After recovering an re-assembiling the parts the PEEK cover was observed to have a decent friction fit when cold, but drop from the nozzle either imediatly upon heating, or soon after.
There does not appear to be any mechanical or adhesive retention other than a friction fit.
At the operating temperature, the thermal expansion coefficient is ~10x greater for PEEK than for brass.
tl;dr: the white plastic bit on the end of the nozzle probably fell off, and I recomend removing it befor leaving the machine printing unatended.
That PEEK cap came off one of my frist prints too - not having it doesn't seem to have much of a difference so I probably concur that removing it before it causes an issue isn't a bad idea.
I'm glad I was able to help.
I've had most of the PEEK caps fall off too. I just make sure that there's no curling of the filament and that the print has started well before I turn my back on the print.