Building a 3D motor printed motor is one thing, ... Though it did delete one: the MK3S removed the optical encoder sensor used in the MK3, and with it the ability to sense filament movement.

Unterpremstaetten, Austria — The AS5305 magnetic linear motion encoder IC from austriamicrosystems targets linear motion and off-axis rotational measurements in applications such as industrial drives, ...

Motor rpm is found by measuring the time between pulses. Divide 60 by the product of the encoder PPR and the period of time between output pulses in seconds to determine rpm: rpm = 60/(PPR t ).