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NEMA 23 gShield config

Posted: Thu Oct 02, 2014 6:53 pm
by FaVo
Hi all,

I'm still planing a Shapeoko 2 with NEMA 23 Motors for the X- and Y-axis.

Now I wonder if the following specs would fit to the gShield v5:

Specifications of the NEMA 23 Stepper
  • Size: 56.4 mm square × 56 mm, not including the shaft (NEMA 23)
    Weight: 0.7 kg (25 oz)
    Shaft diameter: 1/4″ (6.35 mm) “D”
    Steps per revolution: 200
    Current rating: 2.8 A per coil
    Voltage rating: 2.5 V
    Resistance: 0.9 Ohm per coil
    Holding torque: 13 kg-cm (180 oz-in)
    Inductance: 2.5 mH per coil
    Lead length: 12 in
I'm completly new to cnc machines and so any help would be great :-)


Re: NEMA 23 gShield config

Posted: Fri Oct 03, 2014 8:55 am
by FaVo
Or would this motor fit better?
(and it is a little bit cheaper)

  • Current: 2.5A
    Voltage rating: 4.5V
    Resistance: 1.8 Ohm
    Inductance: 6,5MH
    Holding torque: 1.8Nm
    Weight: 1.1kg
    Shaft: 6.35mm
    Steps per revolution: 200 (1.8°)

Re: NEMA 23 gShield config

Posted: Fri Oct 03, 2014 12:32 pm
by Auzze
these are the motors i use on my Shapeoko.. ... 14791.html

Holding Torque:
165 Oz-in/110Ncm
Brand Name:
Current / Phase:
Step Angle(degrees):
Model Number:
Model Number:
NEMA23 stepper motor
Lead wire:


Re: NEMA 23 gShield config

Posted: Fri Oct 03, 2014 9:02 pm
by cvoinescu
The second one is a better fit, because of the lower current and higher impedance. Ideally, you would buy one with a current rating between 1.5 and 2 A; if it's over 2 A, your drivers won't be able to supply it, so you won't get the rated torque. (I chose 1.7 A for my NEMA 23 motors because that's a perfect fit for the driver chips on Pololu modules, the gShield, TinyG etc.)

Re: NEMA 23 gShield config

Posted: Fri Oct 03, 2014 10:16 pm
by FaVo
Thanks for your replies.

I learned, that the gShield can provide up to 2.5A with attached cooling. So that would be the absolute maximum.
But another question is the max torque for the belt... I'm using 9mm width belts that should take a bit more torque than the normal belts but what would be a doable torque in general?

There exits a NEMA 23 Motor that has 2.8A but has a torque of 425oz/in (3NM). But I think that would be too much for the belt?`Or can I use this motor and reduce the max torque via the gShield? I'm not sure what's the best way to go...

Re: NEMA 23 gShield config

Posted: Sat Oct 04, 2014 11:29 am
by cvoinescu
I doubt the belt will be the limiting factor. You don't want a motor heavier than about 700 g, mostly because there's absolutely no point to it. Why would you want to be able to apply, say, 600 N to the gantry or X carriage, when you know that 100 N on your tool will flex the machine too much to be usable?

Re: NEMA 23 gShield config

Posted: Sat Oct 04, 2014 3:09 pm
by aeleus
I'm planning my first build and also thinking of using the gshield with the NEMA 23's listed on inventables. Those motors can draw 2.8A giving 140oz-in.

I understand that the gshield won't provide that current, but my thinking is that I'll have the extra capacity when (or if) I upgrade later.

Any downside of going with the NEMA 23's over the "stock" 17's with the gshield? How much torque can I expect running this way?

Re: NEMA 23 gShield config

Posted: Sun Oct 05, 2014 11:52 am
by FaVo
Since the gShield can only provide 2.5A max you cannot expect the full torque of the motors but that will still be enough.
You can upgrade later to another controller to get the full power out of the motors. You have to think of the y-axis since it has 2 motors on one channel. But that should be ok.

One more thing about the gShield: If you want to use it's maximum current (2.5A) you must install a heat sink! You can't get 2.5A out of it without a heat sink!

The more power your steppers have the better it will be if you plan to upgrade your whole maschine. e.g. double the x and y profiles to get more stiffness... or mount a bigger spindle. Then there will be much more mass to be moved by the motors and a little extra torque will help here...

Like cvoinescu said... it doesn't make sense to use ultra power motors with the stock configuration. That will end up in bending/flexing and loose of accuracy if you use the extra power.
But if you plan to upgrade the x and y axis it can make sense to use bigger motors.

I would say you can use the NEMA 23 steppers listed on inventables without any downside...

Re: NEMA 23 gShield config

Posted: Sun Oct 05, 2014 8:21 pm
by aeleus
Thanks FaVo, that's very helpful.

I just need to figure out what spindle to get now... :?