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View Full Version : What limits stepper motor speed?



Sterob
5th Oct 2016, 10:31 PM
I am fairing new to CNC and have the typical Chinese CNC components in my Router and I was wondering what was the 'weak link' in my machine in regards to motor tuning.
Is it the Break out board or the stepper drivers them selves, or both?
Where would I gain the most benefit from replacing a component.

In my future there may be a Ethernet SS Break Out Board and/or Gecko motor drives.

Just spit balling and interested in peoples experiences.....

Steve

MasterSpoon
6th Oct 2016, 01:01 AM
Bit of an open question there Steve

What is limiting it will depend on what your current setup is, I'm pretty sure the cheap control units / motor drivers were known for being rubbish and binning them in favor of a Gecko unit was generally seen as a good move. I run a Taig CNC Mill with the Gecko G540 but have been running this setup ever since I got the mill so no idea how well / bad the cheaper controllers run.

You need to budget $500ish at least to go to a Gecko setup
Gecko G540 Stepper Drive + 48Vdc 7.3A Power Supply [G540-PS] - US$327.00 : Homann Designs!, Your preferred CNC Supplier (http://www.homanndesigns.com/index.php?main_page=product_info&cPath=53_27&products_id=182)

This runs off your computer's printer port.... so yeah, no laptops, no new computers, you can get a SmoothStepper but that's another couple hundred

I think most people with the cheap 6040 type gantry "Mills" just accept that it's not a quick machine. You need to draw the line in the sand somewhere as to how much you spend to improve it.

BaronJ
6th Oct 2016, 07:02 AM
Hi Steve,

Take a read of this link.

LinuxCNC Documentation Wiki: Stepper Motor Speed Limitations (http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Stepper_Motor_Speed_Limitations)

Ryan in Melbour
6th Oct 2016, 04:04 PM
Steve, that is a good link.
I was going to say the inductance of the stepper motor themselves, closely followed by the size and inertia of the of the motor by your link looks to have it covered.

I just wanted to check what we are talking about when we say speed here as well, is it the speed at which you can run the machine or how quick you can accelerate the motor up to a given speed.

Ryan

Sterob
6th Oct 2016, 09:41 PM
Bit of an open question there Steve

Yeah, I know...sorry....:B
Just looking for general opinions. I thought there might be an obvious limitation I could eliminate first.
I should open the control box up and try to ID the Drivers.



This runs off your computer's printer port.... so yeah, no laptops, no new computers, you can get a SmoothStepper but that's another couple hundred

My BOB is the chinese AKZ250 so its USB. Documents say not to use any other USB devices when using it but thats pretty hard these days.
I don't want to revert back to a Parallel port. As you say, that will make acquiring PC's more difficult.
I would move to a Ethernet Smooth Stepper if I was to change, I think.
Money is not a problem....I'll spend it if its needed.


I think most people with the cheap 6040 type gantry "Mills" just accept that it's not a quick machine. You need to draw the line in the sand somewhere as to how much you spend to improve it.

Yes, I agree. My machine works well ATM and being super fast is not a requirement.
The USB load concerns me as dose what to do if the BOB fails.....move to a ESS I guess.

Steve

Sterob
6th Oct 2016, 09:46 PM
Hi Steve,

Take a read of this link.

LinuxCNC Documentation Wiki: Stepper Motor Speed Limitations (http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Stepper_Motor_Speed_Limitations)


Thanks Baron.:2tsup: Great info there. I'm try to absorb it....lol

I'll have to check my motor inductance's and see how they compare...I'm guessing, not too well( compared to High Quality items )...lol

Steve

Sterob
6th Oct 2016, 09:51 PM
Steve, that is a good link.
I was going to say the inductance of the stepper motor themselves, closely followed by the size and inertia of the of the motor by your link looks to have it covered.

I just wanted to check what we are talking about when we say speed here as well, is it the speed at which you can run the machine or how quick you can accelerate the motor up to a given speed.

Ryan

Certainly is. Baron is a good man...lol

I am referring to traversing speed which include accel and desel rates.

I guess I wouldn't want to buy a new BOB and find the Drives and/or the Steppers can't take advantage of it. All my components may be of similar ability and therefore 'matched'.
I may have to replace them all in one hit to see a well balanced improvement?......dunno.
Steve