0.9 deg/step Motors for a Delta (Anycubic Predator)

ignacmc

Re: Delta stepper upgrade - advice welcome

I have found an interesting motor from LDO: LDO-42STH60-2004MAC 0.60 Nm, 0.9 Degree Stepper. https://caribou3d.com/en/stepper-motors/261-ldo-060-nm-09-degree-stepper-motor-ldo-42sth60-2004mac.html

Could it be a good choice for a Predator? It only costs a couple of euros more than the LDO-42STH48-1684MAC. The more torque the better? I intend to use it with a Duet 2 Wifi or a Duet 3 Mini 5+

dc42

@ignacmc I suggest you check the maximum speed before loss if torque using the calculator at https://www.reprapfirmware.org/emf.html. Longer motors such as that one have higher inductance, so loss of torque starts at a lower speed.

The rated current of that motor is good for Duet 2 and Duet 3, but perhaps a little high for Duet 3 Mini.

ignacmc

@dc42 Thank you for your quick response David. After introducing the 42STH60 data on the calculator I obtain:

Approximate peak back EMF due to rotation per motor: 11.3 V at 200.0 mm/s
Approximate peak back EMF due to inductance per motor: 12.0 V at 200.0 mm/s
Step pulse frequency: 32.0 kHz at 200.0 mm/s
Speed at which torque starts to drop (low slip angle): 204.3 mm/s @ 55.6 kHz
Speed at which torque starts to drop (high slip angle): 280.6 mm/s @ 76.3 kHz

I think I will go for the intermediate model LDO-42STH48-1684MAC (https://caribou3d.com/en/stepper-motors/244-ldo-040nm-09-degree-stepper-motor-ldo-42sth48-1684mac.html). I don't think I need such big torque in my Predator delta printer.
It has a rated current of 1.68 A. Updating 42STH48 values in the calculator now I obtain:

Approximate peak back EMF due to rotation per motor: 9.0 V at 200.0 mm/s
Approximate peak back EMF due to inductance per motor: 12.0 V at 200.0 mm/s
Step pulse frequency: 32.0 kHz at 200.0 mm/s
Speed at which torque starts to drop (low slip angle): 226.9 mm/s @ 61.7 kHz
Speed at which torque starts to drop (high slip angle): 309.7 mm/s @ 84.2 kHz

Does it look better now?

dc42

@ignacmc yes those figures look good, also the -1684 is a better match for the Duet 3 Mini than the -2004.

ignacmc

@dc42 Thanks David. I will order them inmediately.
The fact is that I have a Duet 2 Wifi installed on the printer and a Duet3 Mini5+ waiting on my desk. Wondering if 2209 vs 2660 worth the effort to do the transplant....

dc42

@ignacmc my delta is still running a Duet 2 WiFi. It's a little noisy during homing (I think the homing speed excites a resonance in the motion system) but very quiet during printing, so I don't think I would gain anything except perhaps quieter homing by replacing the Duet 2 with a Duet 3 Mini.

ignacmc

@dc42 Thanks! I will follow your advice and keep the Duet3 Mini for future projects