Choosing 0.9 degree steppers.

bot

Hello,

Choosing a stepper motor seemed almost easy, until I started finding out that I knew next to nothing about how to select one properly, specifically for the Duet Wifi.

Typically, I would go for the highest resolution (0.9) with the highest holding torque (only real indication of torque I know of) with the lowest phase inductance but also current rating close to 2A.

This is the motor I currently plan to use for all axes: ACT Motor 17HM5424, see specs at bottom of chart here: http://www.act-motor.com/product/17hm_en.html

Would this work well, specifically at high rotational speeds? I want to run them geared down 2:1, to give double the resolution on XY.

CodonExe

Step Accuracy of ±5% seems a bit high to me. What kind of gear pack are you going to use?

Aussiephil

Hi bot,

check out this thread https://www.duet3d.com/forum/thread.php?id=5
has a huge amount of information in it.

It's common to under current most of the steppers anyway so anything up to 2.8A with very low inductance is still a good match.

deckingman

@CodonExe:

Step Accuracy of ±5% seems a bit high to me. What kind of gear pack are you going to use?

That's kind of the standard step accuracy that all steppers seem to be spec'd at (at least all the ones I've looked at) but it's non-accumulative. So whether it moves one step or 100 steps, the positional accuracy will still be 5% of a single step.

dc42

I've written a wiki page about this at https://duet3d.com/wiki/Choosing_stepper_motors. The motor you linked to looks to me to be a good choice for the Duet WiFi.

bot

@CodonExe:

Step Accuracy of ±5% seems a bit high to me. What kind of gear pack are you going to use?

Gearing will be done with gt2 belts and pulleys.

And thank you dc42, I was trying to look for that page but forgot where I had seen it. Obviously it's the one place I should have looked first.

W3DRK

For what it's worth, I built my Kossel 250 with OSM 7HM19-2004S 0.9 deg steppers.

http://us.stepperonline.com/09deg-nema-17-bipolar-stepper-motor-2a-46ncm-17hm192004s-p-122.html

You can get 3 of them shipped UPS from California for about $54. While I await my Duet Wifi they've been working perfectly at 1 amp with DRV8825 drivers forced into fast decay mode using pretty aggressive acceleration settings with Smoothieware. Warm to the touch and no missed steps.

Dieter

dc42

@W3DRK:

For what it's worth, I built my Kossel 250 with OSM 7HM19-2004S 0.9 deg steppers.

http://us.stepperonline.com/09deg-nema-17-bipolar-stepper-motor-2a-46ncm-17hm192004s-p-122.html

You can get 3 of them shipped UPS from California for about $54. While I await my Duet Wifi they've been working perfectly at 1 amp with DRV8825 drivers forced into fast decay mode using pretty aggressive acceleration settings with Smoothieware. Warm to the touch and no missed steps.

Dieter

My delta uses the same motor with a different winding, the 17HM19-1684S which is rated at 1.68A rather than 2A. I chose that one because it is a good match for the Duet 0.8.5. For the Duet WiFi, the -2004S is an even better match and should maintain torque up to higher speeds.