Commanded Speeds Vs Actual Spindle Speed
Posted: Wed May 22, 2024 8:42 pm
I recently upgraded the spindle motor on my benchtop mill to a JMC 2.6KW AC servo motor. The servo motor is rated at 2500 rpm with a max rpm of 3000. JMC recommends running it at no more than 2800 for extended periods.
The spindle is belt driven with a 1:8 to 1 ratio. For a max spindle speed of 5000 rpm, the servo would then need to turn 2778 rpms. The servo has an analog instruction gain of 10 rpm/V. Since I want the servo to turn 2778 rpms when Acorn pulls out +10V, I programmed the parameter to 278.
For the Acorn Wizard spindle settings, I set the minimum high speed rpm to 0, and the maximum high speed rpm to 5275 rpm (Since I don't know the actual max rpm).
I then issued the following commands and recorded the actual rpm:
Command Speed ----Actual Speed
m3 S640 ---> 640 rpm
m3 s1000 --> 985 rpm
m3 s2000 --> 1985 rpm
m3 s4000 --> 3845 rpm
m3 s5000 --> 4800 rpm
m3 s5500 --> 5050 rpm
As you can see, while the m3 s640 resulted in an actual rpm of exactly 640 rpms, the actual rpms are incorrect as the rpms increase. So I went back to the Wizard and changed the max high speed rpm to 5050 rpm as observed above. Now all the commanded speeds at 1000 rpm and above are almost spot on, but when I command a speed of S640, the actual rpm is 670.
I tried adjusting the min and max speeds in the Wizard, but no luck. Any idea as to how to fix this?
Thanks... Richard
The spindle is belt driven with a 1:8 to 1 ratio. For a max spindle speed of 5000 rpm, the servo would then need to turn 2778 rpms. The servo has an analog instruction gain of 10 rpm/V. Since I want the servo to turn 2778 rpms when Acorn pulls out +10V, I programmed the parameter to 278.
For the Acorn Wizard spindle settings, I set the minimum high speed rpm to 0, and the maximum high speed rpm to 5275 rpm (Since I don't know the actual max rpm).
I then issued the following commands and recorded the actual rpm:
Command Speed ----Actual Speed
m3 S640 ---> 640 rpm
m3 s1000 --> 985 rpm
m3 s2000 --> 1985 rpm
m3 s4000 --> 3845 rpm
m3 s5000 --> 4800 rpm
m3 s5500 --> 5050 rpm
As you can see, while the m3 s640 resulted in an actual rpm of exactly 640 rpms, the actual rpms are incorrect as the rpms increase. So I went back to the Wizard and changed the max high speed rpm to 5050 rpm as observed above. Now all the commanded speeds at 1000 rpm and above are almost spot on, but when I command a speed of S640, the actual rpm is 670.
I tried adjusting the min and max speeds in the Wizard, but no luck. Any idea as to how to fix this?
Thanks... Richard