ObXidian nozzle comes off on its own after a few prints  

RE: ObXidian nozzle comes off on its own after a few prints

First, I would check whether the problem that the heater block is not tight on the nozzle, or that the nozzle is not held tightly by the thumbscrews. I've had problems with both using a standard brass nozzle. One way of telling which is to try to move the nozzle and watch whether the heater block moves as well (I find placing a mirror on the heat bed makes it easier to see what's happening). I think I now have the heater block tight on the nozzle, just by retightening it from time to time. I've done this 3 or 4 times over a few weeks. If it's the thumbscrews, they might be fractionally short, and in that case you could replace them or just use a M4 bolt of the right length and tighten it with an Allen wrench instead of by hand.

RE: ObXidian nozzle comes off on its own after a few prints

I have no problems with the thumbscrews. It is the nozzle in the heater block. I think it could also be the tension from the heater cable. I have now installed the hot end absolutely stress-free with a pre-bent heating cable (on the lower end) in the following cable order: hotend thermistor cable, hotend heater cable and finally the print fan cable (as in the assembly instruction).

The main reason is of course the expansion coefficient of the different materials, so I'm hoping for a nickel-plated copper block from E3D or Prusa 🙂

RE: ObXidian nozzle comes off on its own after a few prints

This also happens with my nextruder obxidian nozzles on the MK4. The nozzle itself is still tight in the heatsink, it's just the heatblock that gets loose on the nozzle. Thinking about  adding a grubscrew to fix the heatblock to the nozzle. I'll have to acquire some hardware for that as I don't have taps that small. The idea is to use one of the additional screws provided with the heater cartridge.

For me it hasn't resulted in print issues yet, but it is a nuisance.