Makergear M2 Extruder Motor Debugging

While sorting out an extrusion problem on the Makergear forum, I suggested marking the motor shaft and the filament drive shaft to see if the motor pinion inside the gearbox had worn out: if the motor turns and the filament gear doesn’t, then it’s dead inside.

For future reference, you mark the motor shaft thusly:

Makergear M2 - filament drive motor - rear shaft
Makergear M2 – filament drive motor – rear shaft

Two marks on the filament drive gear tell you if the shaft is turning and if the gear is slipping on the shaft:

Makergear M2 - filament drive gear
Makergear M2 – filament drive gear

A closeup of an earlier, much coarser, drive gear:

M2 - Filament Drive Gear
M2 – Filament Drive Gear

It all worked out well in the end!