0.9° extruder motor  

Re: 0.9° extruder motor

Thomas

The MM upgrade uses Bondtech drive pulleys: http://shop.bondtech.se/ec/drivegears/drivegear-kit-175-direct.html

These drive pulleys are much more precise and require exactly 140 steps per millimetre of filament. They are required to ensure sufficient torque during loads and unloads during which time the motor power is increased to around 750 milliamps.

The other thing is that during unloads, high speed retraction is required - the filament is retracted about 92mm at speeds up up to 5400 mm/min so that it does not cool before reaching the cooling tubes where the tip is formed in preparation for the next load.

Your tests showed that it is unlikely for the 0.9 degree stepper to be able to achieve that speed (due to MCU limitations, I guess).

Because of the lower steps of the Bondtech pulleys, the printer's minimum layer height is now increased to 70 microns.

Peter

Re: 0.9° extruder motor

but Thomas did his test just by replacing the 1.8° stepper by a 0.9° version.
wouldn't it be necessary to increase the current to 0.75 amps as well ?

Re: 0.9° extruder motor

but Thomas did his test just by replacing the 1.8° stepper by a 0.9° version.
wouldn't it be necessary to increase the current to 0.75 amps as well ?

No because he is not pulling a blob of filament through PTFE and SS tubing. That's what requires the increased torque (and the Bondtech pulleys).

The stepper drivers can handle much higher speeds, but the limitations are in the motor and the MCU.

Peter