I also do what Chanman mentioned, but instead of setting on LOAD, I use UNLOAD. Keep the lever pressed the whole time, while push the HIPS filament through the extruder and the nozzle, and also when you pull the filament out.
Do it for couple of times until you hear a sound similar to the uncork of a bottle.
When this happen to my Replicator I use a Guitar String, The smallest One, With the Hot extruder I push the string from the bottom of the extruder Until I can see the Other end of the string coming out from the top. To the other side the string will be full of melted plastic, you can clean and repeat the operation.
Usually in makerbot PLA and ABS burn in the extruder, and solidifying, cause of too much temperature, this can be caused by :
-The spring inside the extruder filler has weakened, There is a little spring that push the filament on a toothed pulley, that pulley push the filament in the extruder, if the spring is weak the filament can slip on the pulley, or even stopping, burning.
-Plate not leveled, the extruder hit the plate and the plastic remain in the extruder burning.
-Particular ABS or PLA mixed with wood,carbon,metal etc etc, They have a lot of friction and easily clog the extruder.
Hi, I was having similar issues but I managed to open and do a general clena up inside the extruder. I still got two or three failed print then eventually last night I got one successful print. The extruder seems to be printing very thin. And I noticed that after the raft is done and a few layers of the part are made the platform went a click down in the z axis (increasing the gap between part and nozzel) anyhow I kept observing and it managed to print the part fine. I was observing temperature of the extruder too and it seem to fluctuate between 207 to 213. Not sure why. One reason could be that my printer is in a basement which is cooler and there can be a slight draft. I will print again today and see how it goes. I’m posting updates at www.instagram.com/in rethink if you would like to see. Also try to change the default settings from standard to low and see if it makes a difference When I was printing on standard it failed. The last print I did was on low and it came out nice but the resolution of the print looks like it was on high. I also need to update the firmware and desktop software. Not sure at this point if it will help or make things worse. A little unsure about taking that step. All the best.