Advice selecting stepper motor

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

I have a custom drawing machine, effectively like a CNC machine but with a custom pen holder.

In my current design I have an X and Y motor, but I am going to switch to a more conventional design with two Y motors and an X motor, as here: OpenBuilds ACRO System

So I need an additional stepper motor. My current motors are Casun motors like this: (42SHD0001-24B) High Torque 12V DC NEMA 17 Stepper Motor for 3D Printer - NEMA 17 Stepper Motor, DC Stepper Motor, Stepper Motor Manufacturers

They have a current rating of 0.4A but a reasonable torque. I am struggling to find a matching motor - most seem to have a higher current rating, e.g. 1.68A.

The question is - can I mix motors with different rating? At the moment I am using a bench power supply set at 12V and 0.4A. I'm using an arduino with a CNC shield and A4988 drivers, like this: https://www.amazon.co.uk/dp/B0799JLFV4?ref_=pe_3187911_248764861_302_E_DDE_dt_1

Or should I replace the existing motors and use a matching set of three?

Thanks.

2

You can use different stepper motors but each must have its current set on the driver.

Have mixed NEMA 14 and 17 before with no issues here.

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3

Thanks. It's a while since I set up the shield with the drivers, I will check that they are adjustable. So presumably I would adjust my power supply to the max current rating, 1.68A in this case?

4

LemmyC:
So presumably I would adjust my power supply to the max current rating, 1.68A in this case?

Don't set the current at the power supply because it will drop the voltage to achieve the lower current. Make sure it is set well above the max that could be required so that the power supply limits never kick in.

Set the current limit on your stepper drivers.

I have some of these Sparkfun stepper motors that take 0,33 amps

...R

5

Thanks. I saw that one and thought the torque looked relatively low but translating N-m to Kg-cm to it's similar to my current motors which appear to be 2.65 kg-cm. Do you think these would be capable of moving a gantry along a frame as per the CNC frame cited previously?

6

If I could machine wood with NEMA 14's then that gantry is easy peasy for NEMA 17 :grin:

7

:smiley: :smiley:

8

Your existing motor is a massive 30 ohm, so its not allowing the A4988 to work properly with only
12V supply.

For a drawing robot you probably need a lot less torque than a NEMA17 generates, but they are usually
the cheapest(*), so stick with them, perhaps get some 1.5A ones and try running at 0.75A each, that
may be enough torque and they will run 4 times cooler...

With low-impedance motors like this you'll get much more top speed, even from 12V.

(*) NEMA11's and 8's are very cute (& costly), but much less torque. NEMA14 is more likely to be a
possible compromise but will probably be more expensive than stock '17's

9

MarkT:
With low-impedance motors like this you'll get much more top speed, even from 12V.

(*) NEMA11's and 8's are very cute (& costly), but much less torque. NEMA14 is more likely to be a
possible compromise but will probably be more expensive than stock '17's

I got a batch of 5 NEMA 14 for less than 20 CDN !
They sufficed chomping wood albeit at a reduced rate of feed until I got the hang of CNC / GRBL then picked up a batch of NEMA 17 at waaay more than that.

Something like this would be ideal for just drawing machines.