Dg4s-16035 tuning

Forum for Discussing Mach3/4 related issues

Dg4s-16035 tuning

Postby charles.o.Letellier » Thu Mar 07, 2019 3:33 am

Hello I have 3 dg4s-16035 driving 3 sem mt30h4-44 servos with AEDC-5570-W12 encoders 2500ppr(basically identical to us-digital E5 encoders). I have tuned them with great difficulty to a point where they are not buzzing much. But I am unable the make small .0001 movements without at least 5 to 7 clicks of the mpg in mach3 then the movement is readable with my dial indicator. This is causing lost motion. It is not backlash because I am not changing direction while testing this. The gibs are well adjusted and all drive belts are tight. I have the same results on all axis. Need recommendations is this normal? Tuning these drives has taken years off my life I'm sure and more the 3 months so far, Still not sure it is good. Only way to get a critically dampened wave with servoconfig is by turning the gain very low. Much help needed. Very close to giving up.
charles.o.Letellier
 
Posts: 2
Joined: Tue Jan 29, 2019 2:29 pm

Re: Dg4s-16035 tuning

Postby cncdrive » Thu Mar 07, 2019 5:17 am

If that movement is seen in the Mach3 DRO as you described then it is an issue not with the servo drives, because it is an open loop system in which mach3 does not have position feedback from the servo drives and so if the DRO shows that movements then it is a problem in mach3.
If there is lost motion then it is again not a problem of the servo drives, but there are lost or extra steps on the step/dir lines from mach3 or from the encoder. Servo drives not loosing steps/position (they work in closed loop to the motor encoder) even if they are tuned instable, they only loose steps if the CNC controller does not send the signals properly, sending less or more pulses on the step/dir line or setting the direction signal with incorrect timing or if noise is effecting the lines causing extra or lost steps or if there are lost counts on the encoder. In other words they loose position if there is a problem with the signals the drive receives.
cncdrive
Site Admin
 
Posts: 2957
Joined: Tue Aug 12, 2014 11:17 pm

Re: Dg4s-16035 tuning

Postby charles.o.Letellier » Thu Mar 07, 2019 3:38 pm

"setting the direction signal with incorrect timing "
I don't really know what that means. Can you explain that for me? Does it have anything to do with sampling time selection in the servoconfig? I have know idea what to set that at. I have tried 2 to 7 with not much luck.
charles.o.Letellier
 
Posts: 2
Joined: Tue Jan 29, 2019 2:29 pm

Re: Dg4s-16035 tuning

Postby cncdrive » Thu Mar 07, 2019 4:15 pm

Step/dir interface works like that the controller sends a step pulse and the direction signal in the meantime is high or low and depending on if it is high or low the motor will step one step to CW or CCW.
The direction signal should be valid at the time when the step signal is sent or earlier. (not later).
One possible problem can be if the step signal active low setting is incorrect and so the signal is read by the drive inverted and then it is no more guaranteed that the direction signal is valid on the active edge of the step signal, because when is setup to be the active edge in the UCCNC is not the active edge for the drive. For example the UCCNC sending out active high step signals, so the step signals low to high transition edges are to what the dir signals are synronised to by the software, but the drive is reading the active low edges which is the high to low transition and at that time the dir signal can be incorrect, because the dir signal is sync-ed to the other edge of the signal.
This usually causes some lost steps time to time is what the usualy symptom is for the user.

There is an active low setting in the UCCNC and also in the drive, you can change it on both sides.

(Edit: I see you using Mach3 and I wrote UCCNC, and I'm tired to correct the text now, will not do it, but it works the same with Mach3 or any other software with step/dir interface, so what I wrote is valid for mach3 too.)
cncdrive
Site Admin
 
Posts: 2957
Joined: Tue Aug 12, 2014 11:17 pm


Return to Mach3/4 Discussions

Who is online

Users browsing this forum: No registered users and 1 guest