New stepper motors?

New stepper motors?

Postby BOJO » Sun Apr 06, 2014 4:27 pm

Hi,
I have an old ISEL Gantry table and have just replaced the old ISEL Control rack with a new
based on Axemotion Pulsar and Gecko G230V. Using KAY for driving the machine.
I have not changed my old round motors and are having trouble getting more speed without loosing steps
especcially on the Z-Axis that is rather Heavy with a Suhner UAL 23 1850W spindle.

Will I benefit a lot changing to new Square steppers? Looking at NEMA 23 type with and without brake.
I have a brake for the Z-Axis.
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Re: New stepper motors?

Postby PaulRowntree » Sun Apr 06, 2014 4:47 pm

The magnetic field of old round motors (like the SloSyns) decrease over time, but the newer squares are more stable.

You won't be able to use the Gecko (203?) to their full power with the NEMA23 motors. The 2013 can drive at up to 7A, while the NEMA23's are usually limited to ~3-3.5 A
http://www.geckodrive.com/geckodrive-st ... rives.html
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Re: New stepper motors?

Postby mike1966 » Sun Apr 06, 2014 10:10 pm

nema 34 motors have a lot more power and will work with the gecko drives.I bought mine from cncrouterparts.com they are 7.5amp 960oz only $150
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Re: New stepper motors?

Postby BOJO » Mon Apr 07, 2014 9:34 pm

Thanks for your answers.
I have found adapter plates so that I can use NEMA 34 steppers on my NEMA 23 mounts.
It will add about 1 kg to my Z-Axis but more than double the torque will handle that I suppose.
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Re: New stepper motors?

Postby martin54 » Tue Apr 08, 2014 7:51 pm

If your looking at nema 34 motors to take advantage of the geckos output then you would be best looking at changing your power supply as well, not much point spending money on decent drivers & motors & then running them at 30v DC
If you putting together a system it is best to try & balance the components you use.
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Re: New stepper motors?

Postby BOJO » Tue Apr 08, 2014 9:20 pm

I just found Nanotec NEMA 23 motors with 3 Nm torque 4,2 A
Then I will not have to modify my motor mounts and can use my existing end switches.
I just need new couplings as my shaft is 1/4" and the new motors 8 mm axis.
I Think that these may be a good match for my machine as I have 1,1 Nm old steppers today.
My powersupply is 48V 10A and I that will fit also for these motors?

But will this make difference? I need smoother action for 3D work and more torque for my Heavy Z axis (motor 4,8 kg).

Theoretically these motors are almost 3 times the torque and I dont Think that my old motors are up to the original specs.
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Re: New stepper motors?

Postby PaulRowntree » Tue Apr 08, 2014 9:36 pm

Check out the Gecko site... there is a lot of information there on matching the components. In particular, this page

http://www.geckodrive.com/support.html

is a treasure trove of information. There is a formula (REALLY badly formatted) about 2/3 of the way down that SHOULD read

V power supply in volts = 32 x sqrt( Winding Inductance in milli-Henrys )

My guess is that the strong motors have high inductance, and therefore require a higher power supply voltage to get optimal performance. With 48V, the optimal inductance is only 1.2mH.

Cheers!
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Re: New stepper motors?

Postby BOJO » Tue Apr 08, 2014 10:25 pm

That formula gives 57 V maximum for these motors wired in parallel.
So probably that would work with 48V.
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Re: New stepper motors?

Postby martin54 » Wed Apr 09, 2014 12:56 am

That seems a bit strange because most of the nema 23 motors will run up to about 80v, I have 2-4.4 & 1-3.1 Nm motors on my machine running at about 70v DC.
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Re: New stepper motors?

Postby BOJO » Wed Apr 09, 2014 6:17 am

According to the specs:
http://www.sorotec.de/webshop/Datenblae ... 8L3008.pdf
These are 3.2 mH wired in parallel.
Maybe I am missing something here, othervise these seem to be a good match for My machine.
32*sqr 3.2 = ~ 57 V
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Re: New stepper motors?

Postby BOJO » Sat Apr 12, 2014 10:35 am

Now I have ordered the 3 Nm Nanotec steppers with an original brake for the Z-axis. I will report back with the results. Will it be a big difference to my old round steppers?
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Re: New stepper motors?

Postby PaulRowntree » Sat Apr 12, 2014 2:49 pm

There is no way to answer this, without having the old and new motors side by side to compare.

You could easily hook up a lever arm to each shaft and measure the holding torque with a set of fish scales. Turning torque is tougher to measure, since you want to know the entire torque vs rotation speed curve. I think you will have to ask the CNC machine for this answer ...
Good luck!
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