We Are Learning 3D Printing Through Our Personal Experience…
One of the most annoying issues with 3D printers that extrude thermoplastic materials is when the filament jams inside the extruder causing a failed print and if the problem persists you need to figure out what is causing it. The problem is that there could be numerous thing that are causing the filament to jam and stop extruding from the nozzle and you need to check them one by one until you resolve the issue and are able to continue printing again. One of the most common causes, the one you should start with, is to check the build plate and try to level it again as often after a few prints the position of the build plate may change a bit along the Z axis and this may cause trouble for the filament to either stick properly or to come out normally from the nozzle.
If it the filament happens again after a bit of normal operation after you have realigned the build plate and you are sure that it is not the cause, then you might want to check the thermal insulation of the heated block of the extruder. Usually, as is the case with MakerBot Replicator 2, the heated block to which the nozzle is attached is insulated with special kind of insulation material that is taped with Kapton tape. If the insulation needs to be replaced as it is not functioning properly anymore you may need to replace it or it can cause the filament material to jam inside the nozzle. If you are having trouble with the insulation the actual temperature of the block that melts the filament may be lower than it is needed for normal operation with the specific type of filament used and this may lead to the filament jamming as it is not hot enough to come out at the desired speed from the nozzle. An easy thig you can usually do to check if this is the cause for the filament jam is to increase the extrusion temperature with 10-15 degrees Celsius over the normal one you use and if the jams do not happen anymore then it could be the insulation.
Based on our experience we have found out that anther cause for filament jams could be the nozzle that the extruded thermoplastic material goes through, even though it might seem just fine it can still be the cause. So you should always have a few nozzles as spare to replace them over time as they do wear out and the process is faster if you use composite filaments such as ones that contain chopped carbon fiber or other materials as a part of the filament.
Another different kind of issue that can appear over time that can cause jams or problems with proper extrusion of thermoplastic is the feeding mechanism of the extruder of the printer. If the extruder uses a spring to provide tension to the filament feeding mechanism after a while the spring may soften up and the tension may get inconsistent or too little for proper feeding of the thermoplastic material into the nozzle and as a result cause a jam.
Sometimes the 3D printer jams can be caused by various other things such as low quality filament, the use of exotic material that is not designed to be used with your specific 3D printer and so on, so it is not always easy to figure out what is causing the issues and you need to start checking and eliminating them one by one until you find the culprit.