Heat-creep is one of the most common causes for extrusion related problems.
In order to reduce the risk for this check the following.
- Make sure the cooling fan for the heat-sink is mounted in the correct orientation (blowing towards the heat-sink).
- Make sure the fan blows with full power and is not obstructed.
- Adding thermal paste to the heat-break where it screws into the heat-sink will improve thermal conductivity and can make a big difference.
- PLA is sensitive for heat-creep, do not print PLA in a sealed chamber.
- Has the surrounding temp increased? This is a common problem during hot summers.
Different materials uses different temperature settings, lower extrusion temperature equals higher extrusion force and if the temperature is too low you risk pushing the bowden tube out of the coupling.
Nozzle clogged due to dirt particles
If dirt particles enters the hot-end there is a risk of getting the nozzle clogged if the particle size is in the range of nozzle diameter, smaller nozzles equals higher risk since smaller particles will block the nozzle. A good solution for this is to use a filament filter (a small sponge that the filament goes through and that cleans the filament before the hot-end. Here is a good design from CreativeTools.
Nozzle too close to build surface
If the nozzle is too close to the build surface the extrusion pressure also goes up creating high extrusion forces. Bondtech Extruders can supply about twice the extrusion force when compared to other extruders but at some point it will of course reach the maximum holding force of the bowden connector.
Hot-end cooling fan
If the cooling fan for the hot-end is not cooling the cold section of the hot-end correctly it will lead to heat creep, this will make the filament soft where it shall be hard and stiff and this will lead to problems with too high extrusion force. Make sure that there is nothing that is obstructing the flow of the fan, make also sure it is running at correct speed and also make sure it blows in the correct direction towards the heat sink, not from the heat sink.
Image from E3D showing E3D-V6 hotend.
It is essential that the thermistor has a good contact with the heating block of the hotend. If not it will not report the correct temperature. This in turn might cause an over temperature that leads to heat-creap (heat travels up to the cold section and makes the filament soft and this results in a clog of the nozzle that creates very high extrusion pressure.