I decided to try printing in ABS - and deeply regret it. The nozzle clogged. Tried to purge to no avail. I disassembled the print head. The end of the ABS is visible at the top of the heatsink. I have heated to 260c, but can’t push the plug out. The heatsink is very effective, as I can hold it in my hand while the hot end is at 260c. Short of trying to drill it out, ideas?
You can try blocking the cold end cooling fan which purposely causes heat creep and should soften the filament in the cold side of the extruder. Apply constant pressure to the filament and when it starts to move, unblock the cold end fan and keep manually extruding filament while you cool the hot end down.
If you can do a cold pull at the end then you should be good to go.
Thanks for the quick response! I had completely disassembled the SE print head and did get the ABS pushed through as you suggested. When I took it apart, I noticed there was leaking between the hot end and the heat sink. Are these pieces just pressed together, or am I just not seeing a different method? I was hoping to tighten the joint.
The upper end of the nozzle is supposed to touch the bottom end of the threaded rod that goes from the heatsink to the heater block, that’s what keeps it from leaking. To fix a leak, first heat it up a bit higher than your highest build temp (E3D says 300°C, but I think that’s excessive). Then, hold the heat block steady with a pair of regular slip joint pliers, and use a 7mm box end wrench to tighten the nozzle until it snugs up against the threaded rod inside the heat block. Make sure to keep the pliers away from the heater cartridge leads, they are exposed where they enter the heater cartridge and if you touch them with the pliers you can short them out and blow a fuse on your RAMBo board. VERY IMPORTANT-the proper tightening torque is 30 inch pounds! Too much and you will snap the nozzle off in the heat block - I had a customer who did this once and it was a royal PITA to extricate. the broken off stub from inside the heat block. Too little torque and molten plastic will leak our from the interface of the threads and the heat block.
I apologize for the confusion. I have always tightened the nozzle against the hot end. I was asking whether the hot end should be tightened against the heat sink above it. I didn’t see anything about this on the instructions, but I went ahead and snugged them. I am assuming if there was leak here, snug would have to be a better situation. Things seem to be printing fine, so far!