Stepper motor 128 vs 256 microsteps
Hi,
I own 3 Nema 23 425oz. I want to buy a fourth one, but I don't know what to choose.
1. Which is better, 128 or 256 microsteps ? Is the difference noticeable ?
2. How can I calculate the number of microsteps of my current steppers ?
Could anyone enlighten me :) ?
Thanks a lot !
Re: Stepper motor 128 vs 256 microsteps
The drives control the microstepping amount.
Your steppers are likely 200 steps per revolution, or 1.8° per step.
Re: Stepper motor 128 vs 256 microsteps
I see :) Is there anything noticeable that would push me to use a 256 micro stepping driver instead of a 128 one ?
Re: Stepper motor 128 vs 256 microsteps
I should think that unless you are trying to go very fast there's no point in going more than 16 or 32 microstepping. You certainly I won't get better resolution.
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Re: Stepper motor 128 vs 256 microsteps
Quote:
Originally Posted by
JohnHaine
I should think that unless you are trying to go very fast there's no point in going more than 16 or 32 microstepping. You certainly I won't get better resolution.
I might be wrong, but doesn't increasing the number of microsteps decreases speed ? As I understand, a stepper will go 200 steps per revolution (generally, unless they're half steps or quarter steps), and the driver will use microsteps to make one stepper step. So, 128 microsteps means that the stepper will turn 1 physical step every time the driver makes 128 "electrical" steps. Therefore, increasing the number of microsteps without changing their frequency will increase the time per revolution, thus slowing down the machine.
Or am I way off the track here ?
Re: Stepper motor 128 vs 256 microsteps
Quote:
Therefore, increasing the number of microsteps without changing their frequency will increase the time per revolution, thus slowing down the machine.
Yes, but it doesn't work that way.
The g-code has the speed in it, and the control outputs the correct number of steps to achieve that speed. If you are using 1/32 stepping, than it will need 8 times as many steps as if you were using 1/4 stepping.
The only time it hurts your speed is if you're control can not output steps fast enough.
For CNC use, almost everyone uses 1/8 or 1/10 stepping.
Re: Stepper motor 128 vs 256 microsteps
Quite correct, if you feed the driver with a given step frequency and increase the microsteps the motor will go slower. Therefore the CNC motion controller has to increase the step frequency to compensate to give the same feed rate. But how far it can go will be limited by its own internal clock frequency.
The reason you might want to use a higher microstep number is that if each step asks the motor to move a smaller amount the motor can run smoother, especially if you want it to go quickly. But it's all tradeoffs, as the motion controller may not be able to pulse fast enough, etc. Getting better resolution by microstepping however is not very reliable as it depends on making small adjustments to the relative currents in the phase windings, and the angular position of the motor probably will not respons linearly to these unless it's specially wound - in which case it is probably making other tradeoffs like torque, maximum speed etc!
As stated above, for CNC people don't seem to use more than 8 or 10 microstepping.
Re: Stepper motor 128 vs 256 microsteps
Interesting :) But why are they selling drivers advertised as going up to 256 microsteps since we're only using 1/8 or 1/10 (respectively 8 mcs and 10 mcs) ?
Re: Stepper motor 128 vs 256 microsteps
Steppers and drives are used in lots of applications other than CNC machines, and in many applications, 256 microsteps may work better. Just not for CNC use.
Re: Stepper motor 128 vs 256 microsteps
Quote:
Originally Posted by
JohnHaine
The reason you might want to use a higher microstep number is that if each step asks the motor to move a smaller amount the motor can run smoother, especially if you want it to go quickly.
Actually it is the opposite, microstepping helps reduce cogging and resonance at lower speeds at the expense of some torque. Modern drives will morph to full steps as the speed increases beyond the point where microstepping is useful.
http://www.cnczone.com/forums/gecko-...ml#post1643134
Microstepping: Myths and Realities | MICROMO
bob
Re: Stepper motor 128 vs 256 microsteps
Quote:
Originally Posted by
ger21
Steppers and drives are used in lots of applications other than CNC machines, and in many applications, 256 microsteps may work better. Just not for CNC use.
Ok, I'm happy with that answer :) Well, that's good to know, because I was about to pay 40 more dollars for a 256 mcs stepper+driver pack. I'll go with the 128 one then :) You just saved me $40 :D !
Quote:
Actually it is the opposite, microstepping helps reduce cogging and resonance at lower speeds at the expense of some torque. Modern drives will morph to full steps as the speed increases beyond the point where microstepping is useful.
Good point :)
Re: Stepper motor 128 vs 256 microsteps
What drive do you plan on buying?
Re: Stepper motor 128 vs 256 microsteps
This one, what do you think ?
Re: Stepper motor 128 vs 256 microsteps
They look like Leadshine digital drives, so they should be OK. Hard to tell what you're getting from China sometimes, though.
Re: Stepper motor 128 vs 256 microsteps
Would you recommend something else (so I don't waste my money on chinese surprises) ?
Re: Stepper motor 128 vs 256 microsteps
No, not really, I can't guarantee that anything I'd recommend would be better, as I don't have any personal experience.
Re: Stepper motor 128 vs 256 microsteps
You mean any personal experience with Chinese orders ? Because looking at the number of your posts, you have plenty of experience ;) I'm assuming you always buy your hardware in the US ?
Re: Stepper motor 128 vs 256 microsteps
I've recently purchased two chinese spindles, and two Leadshine AM882 drives. But they won't get used for at least another year, so I can't comment on their quality yet. Those are the only CNC items I've purchased from China.
Re: Stepper motor 128 vs 256 microsteps
I see :) Well, i'll do the experience, since most of what I will order will come from China :)
Re: Stepper motor 128 vs 256 microsteps
Here is an explanation for using high orders of microstepping:
Microstepping: Myths and Realities | MICROMO
Based on that I would suggest that you don't set your microstepping to any more than 10 or 16 though the driver may be more capable. The problem may be that you send the drive a number of pulses that should cause the axis to move a certain distance, but actually the motor can't create enough torque to move at all! As someone said earlier in CNC we tend to use smaller microstep factors as we are moving heavy slides with lots of friction. If you were moving a pointer on a dial or something with very low friction the situation would be different.