jnnewton

I've had my UM2 for a while, but haven't really printed very much (maybe a dozen small objects). I recently tried to print several items at once for a project I'm working on, and It went very badly. The print time was 26hrs. When I came back to check on it, 20+ hrs later, there was filament and printed parts everywhere, the bed was all the way up against the nozzle and the nozzle was still running around in the x and y, scratching / dragging on the bed glass (the bed was not stepping like it was trying to move up though. Bed was still hot, no filiament was coming out of the extruder. I then tried to print a shorter (10 min) print, and everything went fine. So I chalked it up to a one off glitch / bug or g-code error. I loaded up another long print (20+ hrs), and watched it run for about 30min before going about my day. I checked it again about 3 hrs in, no problems, so I went to bed. When I woke up, it had failed again, same manner, bed all the way up on the nozzle, but this time it was still extruding, and it was all up in the fans and just going everywhere. Here's a picture of what it looks like when I come back to it: http://postimg.org/image/pxozlkvz7/ Do we think this is a software or hardware issue? How can I replicate it to verify? Machine: UM2 Software: Cura 15.04 running on windows 8.1 (all updates to OS done). Firmware: "default firmware" Print settings: quickprint "normal" with print support structure. UPDATE: I have found out what causes the mess to start, although I don't know if it's the whole story. The nozzle is dragging in the previous layer, and at some point it will catch enough to pull the part off the glue / bed. I haven't been able to figure out how the plate gets back up to touching the nozzle though.