Hello Guest it is November 20, 2019, 10:05:54 AM

Author Topic: Jogging Servos  (Read 4434 times)

0 Members and 1 Guest are viewing this topic.

Jogging Servos
« on: December 14, 2010, 11:36:22 AM »
I have just started messing around with a servo drive. I am using a Gecko 320X driver, a US digital 500 Line count encoder and a servo from Keling. In testing the servo I can control it from the MDI ok but when I am jogging it, I will work one direction ok but the other direction is hit or miss, and when I do get it to go the other direction it will only go once the I have to the reverse direction a few times then it will allow me to reverse again.

  I think it is in my setting in Mach because the Dro will not move if the motor is not moving.  I hope this is not to confusing the way I have described it.  Does anyone have any idea to point me in the right direction.

Thanks,
Tom

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: Jogging Servos
« Reply #1 on: December 14, 2010, 01:13:35 PM »
Sounds like you have either got duplicate pins assigned or duplicate hotkeys.
Hood
Re: Jogging Servos
« Reply #2 on: December 14, 2010, 02:43:22 PM »
Thanks Hood, I checked the pins and even changed the hot keys but still the same thing.  I forgot to mention that I am using a Smooth Stepper, is there a setting that needs to be set? I am using a C-10 BOB could that cause an issue?

Thanks,
Tom
Re: Jogging Servos
« Reply #3 on: December 14, 2010, 02:46:27 PM »
 I forgot to mention that it all works fine when I am using the stepper motor.

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: Jogging Servos
« Reply #4 on: December 14, 2010, 02:47:33 PM »
It could be the bob I suppose.
If you want to attach your xml and screenset I will see if I get the same problems here.

Hood
Re: Jogging Servos
« Reply #5 on: December 14, 2010, 02:59:54 PM »
Thanks Hood here is my xml the screen is the standard 1024

Tom

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: Jogging Servos
« Reply #6 on: December 14, 2010, 04:58:01 PM »
I see in the SS Config that you have 1MHz enabled for X Y and Z axis, with the motor tuning you have you only need 27KHz or there abouts so I would set that down in the SS config to 32KHz.
 I also see you have high values set for the filtering, there is a good chance that is your problem, try setting the filtering low, maybe around 3 and see if that helps.
Hood
Re: Jogging Servos
« Reply #7 on: December 15, 2010, 12:36:09 PM »
Thanks Hood I seem to have it working, I made your changes and a few other that I don't quite remember but it seem to be working now.

I have another question for you if you don't mind.  I thought that servos were a lot more powerful then stepper motors, I am currently test the servo on my rotary axis on my router, I have it tuned as per Gecko, but as the rotary in turning I can grab it and make it stop.  It seems no more powerful then my stepper motor.  The servo that I am using is from Keling  KL34-180-90 Nema 34 and a Gecko 320X driver.

Was I wrong in my thinking or is there something that I can do to get more torque from the servo?

Thanks,
Tom

Offline Hood

*
  •  25,856 25,856
  • Carnoustie, Scotland
    • View Profile
Re: Jogging Servos
« Reply #8 on: December 15, 2010, 02:12:18 PM »
Servos have a power and torque rating just the same as steppers but the difference is a stepper has its max torque at zero and it decreases the faster you go and it drops off rapidly. A servo has usually also got its max torque at zero but it is usually constant right up to its rated speed and then it also has a peak rating which can come in to play when needed (if your drive can supply the current etc)
Problem is Keling along with many other hobby orientated suppliers mislead you in a way by stating the peak torque in the bold writing. Most industrial orientated suppliers state the rated torque and there is a big difference. Often peak torque is 3 or more times the rated torque so if you have motors that are sold as 9Nm peak then you will likely only have 2 or 3Nm rated torque.
 This is a problem because you look at the steppers on your machine and see they are 9Nm so you get servos of a similar size but then you discover that the stated torque is actually the peak so really you have much smaller motors than the steppers.

Hope that makes sense ::)


Hood
Re: Jogging Servos
« Reply #9 on: December 15, 2010, 10:04:01 PM »
Ahh I see, I guess I should have done some more research. But I only bought one to test.  Do you have any suggestions on where to but good dc servos and drivers?

Thanks again,
Tom