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Nema 23 cant go fast HELP ME!

Posted by burnley1 
Nema 23 cant go fast HELP ME!
November 24, 2015 10:42AM
Hello everyone!
I have a question about RPMs of stepper motors.

I have a kit from Longs motor: Nema 23 425oz motors, 350W 36V power supply and DM542A microstep driver
[www.longs-motor.com]

I can get only like 240rpms with my Nema 23 425oz, If i go faster (with Arduino), the motor just stops and produces strange noises (high pitch noises, but it doesnt move) and vibrations. What to do?All the thing is with no load on the motor shaft.,

Can u please help me what to do?

Best regards
Maticsad smiley

Edited 1 time(s). Last edit at 11/24/2015 10:47AM by burnley1.
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 10:57AM
How fast do you need it to go?


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Re: Nema 23 cant go fast HELP ME!
November 24, 2015 10:58AM
Which controller, which firmware, what step rate? See alse here in the wiki...
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 11:05AM
Quote
enif
Which controller, which firmware, what step rate? See alse here in the wiki...

The motor has 200 steps per rev, on the driver i have set the 400 pulse/rev, so i am halfstepping. I cant do full steps with this controler right?
Controler is in the link: [www.longs-motor.com]
Arduino has 16MHz quartz crystal.

I wanted to go faster, expected like 1500 rpms or more like 2000.

Thanks
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 11:50AM
You can't get a stepper to go that fast, even with no load. You'll need a different type of motor.

You can do full steps with that driver, but at 2000 rpm you need 400k steps per second. I don't think the driver can keep up with that pulse rate.

If you need precision and speed like that you need to look at servo motors and drivers.


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Re: Nema 23 cant go fast HELP ME!
November 24, 2015 12:55PM
Your first link shows a pulse-torque diagram which stops at 5000 halfstep pulses per second, which would correspond to a max of 750rpm. The actual speed you can reach with the 16MHz Arduino, depends also on how your software is implemented.
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 01:01PM
If you only can go 250 RPM something is wrong.
At 3000 RPM = 3000*400/60 = 20,000 steps per second which an arduino should be able to do.
You can run this fast but will have no power at this speed. See torque chart.
What are your current settings?
What program are you using to run the stepper?
Does the motor get warm/hot when running?
How are you measuring the RPM?
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 02:10PM
You're neglecting the motor inductance and detent torque. As you try to drive it faster, you get less current through the windings so torque drops. Eventually the torque falls below the detent torque and the motor can't turn. You might get it to go faster than 250 RPM but I wouldn't expect it to go 10x faster.


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Re: Nema 23 cant go fast HELP ME!
November 24, 2015 03:13PM
I have just this settings from 400 and up to 25600.
So thats why I cant run it with full steps, only half steps or less... true?

But I saw many tutorials and examples where folks turn this kind of stepper motors to run on high speed.
The characteristic - graph torque(pulse) of this motor is in the attachement. The seller sent me that graph, they used the same driver and the same power supply and motor that I used.
Attachments:
open | download - M(pul).jpg (60.2 KB)
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 03:17PM
Quote
george4657
If you only can go 250 RPM something is wrong.
At 3000 RPM = 3000*400/60 = 20,000 steps per second which an arduino should be able to do.
You can run this fast but will have no power at this speed. See torque chart.
What are your current settings?
What program are you using to run the stepper?
Does the motor get warm/hot when running?
How are you measuring the RPM?

Actualy i set the delay in microseconds on the output pin on arduino. The delay time was 500us so it is 0.0005s.
If we calculate this time to frequency we get 2000 Hz - that is 2000 pulses in one second.
That means if i go with 400 steps/ revolution i get 5 revolution per second and 300 RPM.
I measured by counting and compare with the delay i set in the arduino code.

While running on that 300 RPM it doesnt get hot, it gets hot when i speed it up and the motor stops and start vibrating <- there gets hot.
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 03:26PM
The curve shows pps- pulses per second. If you use 1/2 stepping, 400 pulses represents 1 rev. which figures to 17.5 rev/sec which is 1050 rpm where you are getting almost no torque.

Sw5-8 control stepping. The one entry missing from the table is all switches on- that may give you full steps, or might fry the driver. Check the manual.


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Re: Nema 23 cant go fast HELP ME!
November 24, 2015 03:31PM
Quote
the_digital_dentist
The curve shows pps- pulses per second. If you use 1/2 stepping, 400 pulses represents 1 rev. which figures to 17.5 rev/sec which is 1050 rpm where you are getting almost no torque.

Sw5-8 control stepping. The one entry missing from the table is all switches on- that may give you full steps, or might fry the driver. Check the manual.

I also tried the combination of ON ON ON ON - thinked that would be fullstepping but its not, its much more precious than 400steps/rev.
Someone on the forum told me about inductance, that I should have around 90-100 volts of voltage from powersupply for 6.8 mH of inductance.... what do you think?
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 03:59PM
How did you test it? Did you wrote a small sketch where you change the delay between pulses to get a rpm? Did you use an acceleration profile or just go from 0 to 240rpm from the start of the sketch?
Re: Nema 23 cant go fast HELP ME!
November 24, 2015 04:04PM
Yes I put a delay of 500us between logic 1 and logic 0 in at some digital output.
I also tried a acceleration from 0 to something, but motor stops at some rpms...
Re: Nema 23 cant go fast HELP ME!
November 25, 2015 03:01AM
How do you try to accelerate your stepper? Do you made your own sketch? Do you use a firmware like Marlin or Teacup?

Quote
the_digital_dentist
You can't get a stepper to go that fast, even with no load. You'll need a different type of motor.

You can do full steps with that driver, but at 2000 rpm you need 400k steps per second. I don't think the driver can keep up with that pulse rate.

If you need precision and speed like that you need to look at servo motors and drivers.

The standard polulu A4988 can have a maximum of 500kHz. With well programmed firmware and a modern controller this is possible. Just reached 525kHz with Teacup on a STM32F411 at 108MHz.

Edited 1 time(s). Last edit at 11/25/2015 03:15AM by Wurstnase.


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Re: Nema 23 cant go fast HELP ME!
November 25, 2015 06:17PM
Because of the drop-off in torque with RPM, stepper motors can't start at high speeds. You need to start it turning at a slow speed, and then accelerate it slowly.
Re: Nema 23 cant go fast HELP ME!
November 25, 2015 06:44PM
Quote
burnley1
Someone on the forum told me about inductance, that I should have around 90-100 volts of voltage from powersupply for 6.8 mH of inductance.... what do you think?

Let's do some sums. The current in one winding goes from maximum positive, through zero to maximum negative, and back to maximum positive every 4 full steps. So if you run the motor at its full rated current of 3A, the controller has the time for 2 full steps to change the current from +3A to -3A. You are looking for 1500rpm, which is 25rps, so there will be 25 * 200 = 5000 full steps per second, which is one full step every 200us. Therefore in 400us the driver needs to achieve a change in current of 6A. The voltage needed to achieve this is V = L*I/t = 6.8mH * 6A / 400us = 102V. And that doesn't take account of the additional back emf generated by the rotation.

So that person was right. If you don't need the full torque, then you could run the stepper motor at lower current and you wouldn't need so much voltage. But even at half rated current, you would need at least 51V, and the PSU in that package is only 24V. Being realistic, even 500rpm will be difficult to achieve.

A stepper motor is not a good choice for these speeds. A DC motor (brushed or brushless) would be more suitable.

Edited 1 time(s). Last edit at 11/26/2015 05:32AM by dc42.



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Re: Nema 23 cant go fast HELP ME!
November 26, 2015 01:26AM
I like math thumbs up


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Re: Nema 23 cant go fast HELP ME!
November 26, 2015 02:11PM
Re: Nema 23 cant go fast HELP ME!
December 01, 2015 02:44PM
Thanks for your time and thanks to other aswell!!!
I tried powered the drivers to the 50V instead of 36V and I the max rev. per sec grew from like 5 to 6.5 rev/s.
I think i will sell those 3 motors (L=6.8mH) and buy new motors with lower inductance (L=3.8mH).
What do you people think about that?

Im working on my own CNC machine, thats why I need some more speed.
I have ball screws right now but i think i will use toothed rack instead of ball screws for higher speed movement.

Regards from Slovenia
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