M542 driver - motor vibration at low speeds

[birchy]

Jonathon, I understand the basics of machine structure and resonance and that I may need to add dampers at some point, however the motor itself is noticeably vibrating at very low speeds when it isn't even bolted to anything. The machine castings and framework are obviously amplifying the vibration but I think that will always be the case until the motor is made stable.

Regarding the drives and motors, it wasn't a case of "I blame the Chinese", the question I was asking is could it be a problem due to the low cost setup? At the end of the day, you get what you pay for, etc, etc. I bought the motors, drives, BOB and PSU as a 3-axis kit from Zapp a few years ago. If I was buying again, I'd probably buy the parts individually via eBay or AliExpress but go for better quality. Having said that, there seems to be plenty of others using the same setup and not having any issues.

Jonathon - I believe you use (or have used) LinuxCNC? Have you used it with these motors and drives? If so, maybe you could share a known working .ini file? The LinuxCNC latency/jitter test on my PC settles at 15600ns (with CPU at 100% load), so I have this set at 16000 in stepconf. I'm guessing this may be causing the RTAPI error but don't yet know enough about the system to understand what's going on.

[Jonathan]

Jonathon, I understand the basics of machine structure and resonance and that I may need to add dampers at some point, however the motor itself is noticeably vibrating at very low speeds when it isn't even bolted to anything.

The motor is entitled to resonate when not connected to anything. The motor is after all a mechanical system, which will have an associated resonant frequency.

Regarding the drives and motors, it wasn't a case of "I blame the Chinese"

I wasn't being entirely serious there!

the question I was asking is could it be a problem due to the low cost setup? At the end of the day, you get what you pay for, etc, etc. I bought the motors, drives, BOB and PSU as a 3-axis kit from Zapp a few years ago. If I was buying again, I'd probably buy the parts individually via eBay or AliExpress but go for better quality. Having said that, there seems to be plenty of others using the same setup and not having any issues.

Better drivers can help suppress the resonant effects induced by stepper motors, as I mentioned earlier. However that doesn't necessarily mean you need better drivers - if the system works, even with the motor vibrating, you might as well just use it.

Jonathon - I believe you use (or have used) LinuxCNC? Have you used it with these motors and drives? If so, maybe you could share a known working .ini file? The LinuxCNC latency/jitter test on my PC settles at 15600ns (with CPU at 100% load), so I have this set at 16000 in stepconf. I'm guessing this may be causing the RTAPI error but don't yet know enough about the system to understand what's going on.

Yes I use LinuxCNC. The motors on my CNC router are the same and the drivers are PM752 (like you, I bought them from Zapp a long time ago). I'm currently not at home, so can't check what settings I use, however that shouldn't be necessary. The value you've set to 16000ns in stepconf is the one which determines the kernel frequency and thus determines if you get the real time error. I'd find out what the minimum you can set this number to is without the real time error occurring, then add a bit just to be sure.