I managed to blow out my Rostock MAX’s hot end yesterday. Not sure what the issue is yet, but right now I’m suspecting a combination of back pressure and too high a temperature (thermistor was reading 240C, but I don’t know how accurate that is).
As a result, the PEEK insulator bent to a noticeable angle (I should have snapped a photo, but I’ll guess 30 deg or so) during a print and I hit the emergency stop and manually removed the Bowden & filament.
The upper mounting section came off easily, but I had to apply quite a bit of force to get the nozzle off - when it did, it did so with a piece of the PTFE liner and some filament inside. That’s soaking in acetone now.
Separating the heating block and the PEEK insulator is likely to be a problem - I may need to drill it out in the end. I’m strongly tempted to replace the insulator with a machined heatsink - with the PEEK, the Bowden clamp was still too hot to touch, which suggests a large melt zone. I also need to find a better way of attaching the thermistor than the RTV silicone I was using.