512,393 active members
2,733 visitors online
Register for free
Login
Page 1 of 4 123
Results 1 to 12 of 39
  1. #1
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Lets talk about encoders

    Hi everyone...So I'm fairly new to the world of encoders and I'm trying to understand why a lot of servo drives have options for different count/rev encoders. I come from the world of Mach3, and it would seem that the servo drive could be dumb to that so long as the steps/unit is set correctly in mach3 config.

    So the real reason behind my questioning, is I want to add linear encoders to my mill, but I highly doubt the counts/distance will be an even number line on a rotary encoder. so how does that effect the drive? I would think that so long as I have a quadrature encoder and set my steps/distance correctly in mach3 that this would work fine. maybe?

  2. #2
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    34659

    Re: Lets talk about encoders

    What are you doing with the encoders? And what kind of motors/drives are you using? Typically, the encoder data has nothing to do with the drives in Mach3.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Re: Lets talk about encoders

    currently I'm running some closed loop steppers from leadshine, which have a shaft encoder built into the stepper. I'd like to actually use a linear encoder to replace it the rotary encoder.

    Yeah, and I guess I don't understand the relationship between mach3, the drive, and the encoder. I know mach3 has nothing to do with the feedback loop, but how does the drive interperate the signal from mach and from the encoder? logically I would think if mach sent 5 pulse signals, the drive would want to read 5 encoder signals. and any deviation from that is the error read by the drive.

  4. #4

    Re: Lets talk about encoders

    Linear encoders are all metric as far as I know. Normally available in resolutions of 0.1, 0.5, 1, 2, 5, and 10 microns, this is true for both glass and magnetic scales. 1 micron resolution = 25400 pulses / inch, or 0.000039 inch / pulse.

    If you are planning on closing the loop at the drive level, I don't know how a drive would react to being fed with an encoder that it was not calibrated for. Depending on the drive, it may be possible to set the scaling.

    To really take advantage of linear encoders, you would need a real motion controller between Mach3 and the drives and close the loop at the controller. Dynamotion or Galil would be good choices.

    I have 1 micron magnetic linear encoders on all of my machines and have had very good luck with them.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    34659

    Re: Lets talk about encoders

    but how does the drive interperate the signal from mach and from the encoder?
    I think that they are two separate loops. Or the steps/unit is locked to the encoder resolution.

    Mach3 knows nothing about the encoder. It just sends steps to the drive.

    The drive just makes sure the motor goes where the steps have told it to go.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  6. #6
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Re: Lets talk about encoders

    thanks for the responses guys. I'll take a look at my drivers to see if the encoder is truly configurable or if it's just preset values.

    I've never really looked at the dynamotion board as I din't know they had a mach3 plugin. But I wish I had known about it before I bought my smoothstepper boards. haha.

  7. #7
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Re: Lets talk about encoders

    According to the manual, I can set that to be any value I want. So maybe I'll give that a try first.

    but i guess on that topic, what exactly does the drive do with that information? Maybe for this drive it helps determine the microstepping?

  8. #8

    Re: Lets talk about encoders

    Quote Originally Posted by CS900 View Post
    .............. what exactly does the drive do with that information? Maybe for this drive it helps determine the microstepping?
    Lets say Mach3 sends out 100,000 pulses, that drive takes that information and moves the motor (or table) 100,000 encoder pulses. With the loop closed at the drive, the drive looks at the current position and keeps moving the motor until the 100,000 pulse distance is reached.
    Jim Dawson
    Sandy, Oregon, USA

  9. #9
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Re: Lets talk about encoders

    That's what I thought was happening. Seems like the encoder itself it's fairly arbitrary and pretty hopeful I can close the position loop at the drive.

  10. #10
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    34659

    Re: Lets talk about encoders

    What drives do you have?
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  11. #11
    Registered
    Join Date
    Aug 2006
    Posts
    575

    Re: Lets talk about encoders

    there's a link in post #3 to them.

  12. #12
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    34659

    Re: Lets talk about encoders

    I would think that the encoder resolution needs to match the one on the motor, or it won't work correctly, as the drive is expecting 1000 counts/rev? (Or is it 4000?)
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

Page 1 of 4 123

Similar Threads

  1. Lets talk spindle lubrication
    By CS900 in forum Benchtop Machines
    Replies: 2
    Last Post: 03-30-2016, 06:08 PM
  2. Lets Talk About End Mills
    By Evanrigs in forum Uncategorised WoodWorking Machines
    Replies: 1
    Last Post: 09-03-2014, 01:29 AM
  3. lets talk bearings (Mini Mill x2)
    By ZipSnipe in forum Mechanical Calculations/Engineering Design
    Replies: 9
    Last Post: 05-03-2013, 06:57 AM
  4. Lets talk about BRUTE machines....WOW
    By carbidecraters in forum Uncategorised MetalWorking Machines
    Replies: 13
    Last Post: 05-16-2010, 08:23 PM
  5. Lets talk financing
    By carbidecraters in forum General MetalWork Discussion
    Replies: 11
    Last Post: 04-18-2006, 08:00 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •