DMM DYN 4 spindle servo tuning tip
- dbtayl
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14 Feb 2026 02:50 #342921
by dbtayl
DMM DYN 4 spindle servo tuning tip was created by dbtayl
Want to get information out there that might help somebody. Short version: If you're having trouble with a DMM DYN4 used as a spindle getting "lost phase" errors and not being able to hit the top rated RPM, lowering the gains might help.
Longer version:
My little baby BT30 benchtop mill is set up with a DMM DYN4 servo as the spindle- drive is DYN4-H01, motor is the 1 kW 86M-DHT-A6MK1. I'm using it in position mode with quadrature inputs. I don't have an index pulse on it, so I haven't tried rigid tapping. The spindle is driven with a 28:44 motor:spindle pulley ratio, using GT3 belts.
DMM was very helpful in getting it set up- provided a tuning procedure and debugging help. Great customer service. Despite that, performance was disappointing- notably the "lost phase" errors, which occurred at high speeds (4000 motor RPM and above, or thereabouts) or under anything but light cuts. Checking the drive's diagnostics page, I could also see the "on position" signal getting inconsistent as RPM increased, even under no load.
I figured it needed more gain- not holding position under no load -> needs more gain. That made things worse, if anything. Adjusting the torque constant (current smoothing) and integration gain settings (two things DMM clearly instructed NOT to change) maybe kinda helped a little bit, but still far from what I expected.
I eventually got fed up and decided to try LOWER gains... works great. Totally unintuitive to me. The chatter I was experiencing cutting 304 stainless also seems to have been resolved. I'm still working up to pushing the limits of the machine, but so far I haven't seen anything to indicate those gains will be too low under heavy cuts.
Every machine is probably different, but FWIW IIRC I ended up with a main gain around 20 and a speed gain around 15. IIRC the integration gain is back at 1 and the torque constant at 127 (per DMM recommendations for this application), but I'm not at the machine to check any of those numbers right now.
Hope that helps somebody! Mods feel free to move if this belongs somewhere else.
Longer version:
My little baby BT30 benchtop mill is set up with a DMM DYN4 servo as the spindle- drive is DYN4-H01, motor is the 1 kW 86M-DHT-A6MK1. I'm using it in position mode with quadrature inputs. I don't have an index pulse on it, so I haven't tried rigid tapping. The spindle is driven with a 28:44 motor:spindle pulley ratio, using GT3 belts.
DMM was very helpful in getting it set up- provided a tuning procedure and debugging help. Great customer service. Despite that, performance was disappointing- notably the "lost phase" errors, which occurred at high speeds (4000 motor RPM and above, or thereabouts) or under anything but light cuts. Checking the drive's diagnostics page, I could also see the "on position" signal getting inconsistent as RPM increased, even under no load.
I figured it needed more gain- not holding position under no load -> needs more gain. That made things worse, if anything. Adjusting the torque constant (current smoothing) and integration gain settings (two things DMM clearly instructed NOT to change) maybe kinda helped a little bit, but still far from what I expected.
I eventually got fed up and decided to try LOWER gains... works great. Totally unintuitive to me. The chatter I was experiencing cutting 304 stainless also seems to have been resolved. I'm still working up to pushing the limits of the machine, but so far I haven't seen anything to indicate those gains will be too low under heavy cuts.
Every machine is probably different, but FWIW IIRC I ended up with a main gain around 20 and a speed gain around 15. IIRC the integration gain is back at 1 and the torque constant at 127 (per DMM recommendations for this application), but I'm not at the machine to check any of those numbers right now.
Hope that helps somebody! Mods feel free to move if this belongs somewhere else.
The following user(s) said Thank You: tommylight
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