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ForumCSMIO/IP controllers and Software - discussion forum: CSMIO/IP with simCNC softwareCan you suggest the appropriate v …

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Can you suggest the appropriate values or ratios of the motor speed, acceleration, and jerk among the values shown?

#1 · 20 June 2025, 10:09

Hello
I am operating an old nc milling machine converted to an ac servo using csmio-a and simcnc. The reason is that speed errors frequently occurred during PID tuning recently, so after researching, I found out that it was a problem with the motor tuning variables, as shown in the attachment. Can you suggest the appropriate values or ratios of the motor speed, acceleration, and jerk among the values shown? I would really appreciate it if you could divide the stiffness of the machine into upper, middle, and lower and suggest the values for each. For example, if the speed is 50, the appropriate acceleration and jerk values are 1000~1500 and 10000~12000, respectively.

For reference, the values in the attached file are the values that worked well after a long time. Originally, they were 100, 1500, 50000, which are the default values of simcnc. At that time, an error occurred every time.

Uploaded files:

#2 · 21 June 2025, 14:14

Hi, Could you please clarify what kind of "speed error" you're getting?

Is it a specific message from SimCNC or the servo drive?

Any screenshots, error codes, wuld really help to better understand the issue.

#3 · 23 June 2025, 23:58

There are two errors that occurred, as shown in the attached file. I assume that the PID error is caused by simcnc and the speed error is caused by a servo alarm (mostly overcurrent). When I first started the machine, these two errors kept occurring, and I thought the cause was an external scale or PID tuning problem, but I recently determined that the speed, acceleration, and jerk values of the motor tuning were the cause. In particular, the speed value of the motor tuning is set to 100 by default in the motion kit, which is 100mm per second, so it is a very fast speed of 3600mm per minute. When I lowered this to 30mm per second for the z-axis and 50mm per second for the xy-axis, everything went smoothly. So I roughly set the acceleration and jerk values to 1500 and 20000, but I wrote this because I was curious about the appropriate example values for the acceleration and jerk values. Please refer to it.

Uploaded files:

#4 · 24 June 2025, 11:20

I don’t know your particular machine, but V:100, a:1500, and j:50000 seem reasonable. If your machine was working with those settings before and has now started experiencing issues, it could indicate mechanical problems or drive-related issues. In any case, those values are relatively “gentle,” but as I mentioned, it really depends on the specific machine and drives you are using.

#5 · 25 June 2025, 09:06

Thank you for your reply. I guess I'll have to adjust the acceleration and jerk values based on 1500 and 50000. The absolute range of the value changes is quite large. Anyway, thank you for your valuable reply.

#6 · 26 June 2025, 10:43

I’d really recommend focusing on diagnosing the root cause of the issues. Based on what you’ve described earlier, your configuration parameters shouldn’t be causing problems like "overcurrent" errors.

Please check the mechanical setup, connect to the servo drive using diagnostic software if possible, and monitor values like motor current, following error, etc. Reducing dynamics might help temporarily, but in my opinion, it’s not a good long-term solution.