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I ran into a strange issue that I've not seen before. While jogging a motor on my test setup, I noticed the motor not spinning at full speed.
With my steps/unit set at 12800, any velocity settings above 640 cause this to occur. Is it a strange coincidence that it's exactly 20%? It sounds like the motor accelerates to full speed, then slows down. As I increase velocity above 640, the motor actually spins slower. This is jogging at 100% jog speed, but it also does it during rapid moves from MDI.
I have the kernel speed at 200Khz. When set to 100Khz, I don't see this issue, but can't spin the motor as fast.
At 200Khz, the max velocity is about 890, but the motor spins fastest at 639-640, and goes slower as I increase velocity.

I hadn't seen this behavior in the past, and the only thing that's changed is swapping my MB2 for the UB1 breakout board.
I tried UCCNC versions 1.2037, 1.2043, and 1.2047.
I'm using a Leadshine AM882, and I actually tried two different drives. The drives were originally set at 1/32 microstepping. I changed it to 1/16 with no difference.

I made a quick video. Listen to the sound of the motor, and you can hear the difference. I didn't record it at 890 velocity, but it spins much slower at that setting.

I'll send an email to Weerasak at CNC Room and ask his opinion.

https://youtu.be/TAEueiJ9_S4

Also, the UCCNC is displaying the velocity that the motor should be spinning, not what it actually is.
So, if I set the velocity to 800, field 868 will show 800, when the motor is clearly spinning much slower.

Hi Gerry,

I reported the issue to my collegue, he will check it out soon.

Hi Gerry,

You have never experienced this behavior with MB2. Was it run in 5LPT mode? Remember that the UB1 has its own board ID with minor change of firmware.

If you experienced it with both 5LPT and UB1 mode already, I guess that I will leave it with UCCNC team to find it out in UCCNC software.

Yes, I changed the jumper and tried both 5LPT mode and UB1 mode, and there was no difference.
Thanks for looking. Can you try what I did and see if you see the same issue?

Gerry,

My collegue started to check this issue.
He set the steps per units and velocity just like on your video and how you described, he checked velocity settings 640 and 800 and a few other values.
He tried to jog 100% and around that speed and G0 rapids from MDI. He measured the step frequency and also connected a motor to hear the sound pitch differences by ear.

So far he could not reproduce the issue.
Could you please send me your profile file with which this issue happens?
My collegue thinks it is probably some other settings dependent which he could not figure out what it could be, so having the profile file would be helpful.

Profile attached.

If you need a copy of my screenset, let me know and I'll send you a link.

Thanks Gerry, I will give it to my collegue now and will report back asap.

I'll go out and try a new profile, with only one motor setup, to see if it makes any difference. Just need to warm up the garage first.

OK, thank you for that, it could be also helpful to know if for example the issue could be reproduced at you with the default not yet changed profile.