I wanted to provide the extruder stepper motor with a smaller drive gear so that this brings a little more force on the filament and clogs the nozzle less easily. When using a smaller gear, the position of the direct extruder MK8 no longer fits, so I redesigned, printed and replaced the parts around the stepper motor. As material I used PETG, because PETG tolerates a bit more temperature compared to PLA. I was able to successfully test printing with temperatures up to 260° with the setup.

Smaller gear -> more pressure

If the filament is squeezed into the nozzle with more pressure, the nozzle will not clog as easily. In addition, the original setup has too much freedom of movement after the drive for printing with TPU, whereby the soft material easily forms a loop which then does not land in the nozzle, but comes out to the side. For printing TPU, I was also able to achieve an improvement here.

Direct drive to 7.5mm

Originally, the MK8 uses an extruder gear with 11mm diameter, here in direct comparison with a 7.5mm gear:

For the use of the 7.5mm gear I have renewed the construction around the stepper motor as follows:

E Steps/mm

To ensure that enough filament is conveyed, I had to set the value E Steps/mm on the printer display from 93 to 145.

Conclusion

Admittedly, I am not sure if this should have been the case. A clogged nozzle usually happens when I change from PETG to PLA, but mainly because I process PLA with less temperature and then there might still be some PETG left over: Nevertheless the change minimizes the probability of a clogging, because the filament is squeezed with more force mostly nevertheless by the nozzle.
Filament feeding problems still have a cause. For example, in my printer, after some time the PTFE tube dissolved inside. See: MK8 extruder, Nozzle: Nozzle clogged - PTFE Teflon used up