how to salvage a failed print

Today I was printing a part on my prusa and it stopped extruding. I still don’t know why, but I do know that the printhead was a full cm above where the piece was, and it was happily just spinning along.

Since my part was essentially the same outline at the point where it was as where it stopped extruding, I thought up a quick hack to salvage the print.

In pronterface I paused the printer. Next I got it extruding again. I typed M114 and then enter into the dialog box at the bottom right corner. That sends a command to the printer to report back its position. Check out the Z value that it gave back to you. I then jogged the extruder down until it was just smushing into the print. I typed “G92 Z” ,then the z value from above, and enter.

That tells the printer that it is now at the point that it was really at previously. Since I lost all of that print while the printer wasn’t extruding, it essentially just chops that part out and tells it to start printing on top of the print again. I feel like this isn’t making any sense, so hopefully I can clarify it later. I then hit resume, and watched my new (shorter) print finish up!

Note: as you can see in the top photo, there is a line that is probably pretty weak on that part. A bit of ABS glue will definitely help strengthen that up (while making it look ugly) and I think that if I were faster to catch the stopped extrusion, then the print still would have been hot enough for it to bond properly.