Spun nut
I'm trying to assemble an old Mk3 kit plus a MMU2S upgrade, though my issue is kind of general. I'm on that step where you mate the extruder to the X-carriage (with the two screws that sort of go behind the extruder). While checking that nothing was binding, I realized that somehow I managed to spin one of the nuts in the extruder body that anchors one of the 40mm bolts which holds together the two halves of the extruder. I think I may have initially had a crossthreading that I fixed, but that put too much stress on the plastic.
So I can assemble the part but if I try to tighten down, it just spins instead of letting me tighten it properly. And the nut is set pretty deeply down in the part; I tried to get it to "bite" by using a battery powered screwdriver but that just heated up the plastic and let the nut bed in a bit more without actually binding it.
Any ideas how I might save this without ordering another part?
RE: Spun nut
If you don't particularly care about getting the nut back out in the future (hex nuts are easy to find, the square ones a lot harder outside of Europe)... superglue, or melt it in more by heating it with a soldering iron? Even if it doesn't adhere to the PETG, it should act as a filler and at least stop it spinning enough that you can get far enough to print a new one yourself.
RE: Spun nut
I used rubber cement to help hold the nuts in place while assembling. But if you are already at that place where the nut is buried - something less viscous would be better. Keep the screw in place, but loosened a bit, and try dabbing finger nail polish or an enamel paint into the slot. Let it dry and try again.
RE: Spun nut
I had exactly the same issue with a new mk3s kit so contacted support who are sending a replacement part.
RE: Spun nut
So in the end I figured out that I could use a shorter screw and slowly tighten things down quite a bit so that the nut bedded in. Then I gently loosened the screw and by some miracle the nut stayed in place. I quickly assembled the part and went on. It doesn't appear that anything was improper afterwards. If I have to disassemble the extruder in the future (which I'm sure I will) then I'll have to hope that the nut doesn't spin again, but by that point I should have been able to figure out PETG and print a spare set of parts.