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Slow stepper speeds
« on: March 13, 2020, 06:39:51 PM »
I have just finished a router with Nema 23 motors driven by Gecko 251 drivers controlled by an ESS with MB3 breakout board with Mach4  running on 24v.

In motor settings I have steps set to 250/ unit ,  acceleration 60 and velocity various settings right up to 3000mm/min.
Dimensions are accurate  for the 8mm leadscrew

The highest speed I can achieve  on all axis is about 500mm/ min.
Should I be able to get any higher speed with this setup?

Maybe it has been a poor choice of steppers and drivers.

Art
Re: Slow stepper speeds
« Reply #1 on: March 13, 2020, 07:07:55 PM »
Try upgrading your power supply to 48 volt. Best case your maximum velocity could almost double.
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: Slow stepper speeds
« Reply #2 on: March 13, 2020, 08:18:04 PM »
Hi,
I agree with Steve, use the highest voltage power supply your divers will tolerate. Geckos have a superb reputation for
reliability, if they say 80V...then use 80V.

What model steppers do you have? In particular do you know the inductance? It is a little understood fact that the inductance
of a stepper determines how badly the torque will degrade with stepper speed.

Most stepper manufacturers make high holding torque (desirable) steppers but with commensurately high inductance (highly
undesirable) because they can make them cheaply and thereby appeal to first time buyers.

If you absolutely require the fastest possible axis speed then you will probably have to replace your steppers with the
LOWEST POSSIBLE inductance. This might mean that a (say) 300 oz.in stepper of 1mH inductance is a better choice
than a 600Oz.in stepper but 6.8mH because the smaller stepper will still have useful torque at 1000rpm whereas the bigger
one stalled at 300 rpm.

Craig
My wife left with my best friend...
     and I miss him!
Re: Slow stepper speeds
« Reply #3 on: March 14, 2020, 02:55:30 PM »
Thanks for your replies.

Raising the voltage to 48 volts has made no difference to the speed. The inductance of the motors are  3mH and they are 2.8A motors. I have them set to 2.7A as I only had 2.7k resistors.
Maybe I am expecting too much but looking at some videos of similar machines  on youtube my machine seems much slower.

Art

 
Re: Slow stepper speeds
« Reply #4 on: March 14, 2020, 04:04:53 PM »
While 3 mH is not great, neither is it that bad. With your setup I would expect 1000mm/minute or better, possibly even 2000 mm/minute.

When you state that 500 mm/minute is the best that you can get, do the motors stall or simply refuse to go any faster? If stalls are the issue, try running the motor with it not mounted to the machine and see if it will go faster unloaded.
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: Slow stepper speeds
« Reply #5 on: March 14, 2020, 04:21:09 PM »
Hi Steve,

They just refuse to go any faster. They are very smooth no skipping steps or stalling.
I remember setting up my mill and lathe on mach3 many years ago you could make them skip and stall but that was a very different system.
The machine is a workbee router but I decided not to use the duet controller. I did see that with the duet a rapid of 2000mm per min was possible.

Art
Re: Slow stepper speeds
« Reply #6 on: March 14, 2020, 04:55:52 PM »
If the motors keep running at 500 mm/minute but do not stall, then I suspect a configuration error, possibly in your ESS setup.
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: Slow stepper speeds
« Reply #7 on: March 14, 2020, 05:31:16 PM »
Hi,
the ESS plugin has the ability to assign motors to axes and output pins of the ESS but it has NO motor tuning
features, motor tuning is the sole responsibility of Machs Control plugin.

Craig
My wife left with my best friend...
     and I miss him!
Re: Slow stepper speeds
« Reply #8 on: March 14, 2020, 06:32:54 PM »
I must admit to not being very familiar with the details of setting up a SmoothStepper, especially with Mach4.

There was an option for "Controller Frequency" in the configuration menus for the Mach3 plugin and that could influence how the SmoothStepper generated pulses. It seems that is no longer present in the Mach4 plugin configuration, so it should not be an issue.

I am still curious if Mach4 thinks it is moving the motor faster than 500 mm/minute. In Mach3 there was an on screen DRO showing the current instantaneous velocity. Is there an equivalent in Mach4 that I am overlooking?
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: Slow stepper speeds
« Reply #9 on: March 14, 2020, 07:20:42 PM »
Hi Steve,

Quote
In Mach3 there was an on screen DRO showing the current instantaneous velocity. Is there an equivalent in Mach4 that I am overlooking?

Yes, there is, see attached.

I think your suggestion is good...to OP: MDI some commands, for instance g0 x300 (assuming mm units here) and observe the feed rate
DRO. Does the DRO show what you believe to be the correct G0 rate?

How about MDIing g1 x200 f300....does the feed rate DRO show 300mm/min. If not, why not?

Craig
My wife left with my best friend...
     and I miss him!