Can't Alter Axis Velocity

[CL_MotoTech]

So I conservatively set my X&Y to 140 ipm while I tested the machine but would like to change it to faster now that all is working. With the machine in estop, I click in the velocity field, type "160", hit enter. The number is in the field. I can click in other fields, the 160 stays put. When I hit apply the velocity reverts, except it's no longer 140, now it's like 140.216 on the X. Meanwhile the same is happening on Y, except the value it revers to is 139.953. If I enter "140" and hit enter, click apply or save, it reverts back to that 139 number. And of course I get a warning on startup that X&Y should be set to the same velocity, but I can't get them to change.

Any ideas?

[Robertspark]

What are your steps per unit for EACH axis?

What is the kernel speed setting for the UCCNC motion controller?

[CL_MotoTech]

25hz.

Something like 10,100 steps for each axis after calibration.

I guess I am limited by Kernal frequency. That makes sense in retrospect.

Aren't most stepper drivers basically limited to 25hz? I'll step up to 50hz and see what happens.

[Robertspark]

Cheap drives tend to be 100khz.... Better drives 200khz.

140ipm / 60 X 10,100 is your problem

Do you really need 10,100 steps per inch!

1 step equals 0.099 thousands of an inch....

[cncdrive]

The issue is that your steps per times the velocity is higher than the kernel frequency.
In this case the UCCNC will lower the velocity parameter to the maximum possible with your steps per value.
You could make the velocity higher with setting the kernel frequency higher. (If your drives are OK with that, however if they are not then there is no point to set them higher in the UCCNC.)

[CL_MotoTech]

I'm using an MX3660 to drive X,Y,Z. Then a Gecko G540 on C. I'll have to find the manuals to figure out what kernal frequency they will handle as I don't recall.

I've upped the Kernal Frequency to 50hz for now. I'll give it a shot.

As to why I am using 10k steps per inch, the Gecko is tied to 10 microsteps, so I just started there with the MX3660. With 5tpi screws, that's just how the math works out. I could set the MX3660 for half that, or even less.

With Mach I have successfully run my machine at 180ipm on X&Y, so I would expect similar or better performance from UCCNC. That said, I'm not really married to that velocity, I can run less and be okay with it. The machine is small enough (G0704( that really fast rapids really don't mean much.

[Robertspark]

Mx3660 will handle 200khz
https://www.google.com/url?sa=t&source= ... 5810168409

G540 will also handle 200khz

https://www.geckodrive.com › ...PDF
Web results
g540 manual - Geckodrive

Note kernel frequency is in kHz not Hz....

Your math is correct for the leadscrew
1/ (5tpi /( 200 * 10)) = 10,000 steps per inch.

[CL_MotoTech]

Thanks gentlemen. I appreciate the help.